The Moragne Plumeria

Fifty years ago, a dedicated amateur made the first controlled crosses of these fragrant tropicals.

Richard A. Criley & Jim Little
Published April 01, 1991

Plumerias, which are native to the semideciduous forests of southern Mexico and south into Panama, were described as early as 1522 in the Badianus Manuscripts by Francisco de Mendoza, a Spanish priest who was one of the first explorers of the region. According to this collection of Aztec lore, the Indians used the plants for medicinal purposes that ranged from poultices to emetics. Soon the hardy shrub with beautiful fragrant flowers was a favorite of the Spanish, who planted it around their churches, monasteries, and cemeteries, and took it with them as they explored the world.

The plumeria has also acquired religious significance in India, where it is known as the temple tree or pagoda tree. There, Buddhists and Moslems regard the tree as a symbol of immortality because of its capacity to produces flowers from stems severed from the parent tree. Hindus use the flower as a votive offering to the gods.

The flower’s botanical name honors the seventeenth-century French botanist, Charles Plumier. Some horticultural historians say that the common name, frangipani, was derived from the French word, frangipanier, meaning coagulated milk, which its sticky white latex resembles. Others believe it honors a twelfth-century Italian who compounded a perfume similar to that of these tropical flowers that were discovered some four centuries later.

Because Plumeria flowers and leaves come in so many forms, taxonomists once held that there could be forty-five or more species. Of course, these variations are not enough to justify naming a separate species. The “lumpers” of the taxonomic trade-as well as Hortus Third-now say there are perhaps only seven or eight species, and that most of those in the popular books on tropical flowers are really only variations of Plumeria rubra. “Splitters” among taxonomists still dissect out some other species, as do floras of Mexico and other Central American countries.

The first plumeria was introduced into Hawaii in 1860. It was a yellow brought in by Wilhelm Hillebrand, a German physician and botanist who lived in Hawaii from 1851 to 1871. The first red is thought to have arrived from Mexico around the turn of the century, either via a Mrs. Paul Neumann, wife of a consul stationed in Honolulu, or a Mr. Gifford, landscaper for the Royal Hawaiian Hotel. The white ‘Singapore’ plumeria was brought to Hawaii in 1931 by Harold Lyon, director of a sugar cane research station, from a large collection established in 1913 at the Singapore Botanical Gardens.

Since then, natural hybridization has given rise to many variations in form and scent, making them popular among collectors, who in 1979 established their own admiration society for this plant, the Plumeria Society of America.

But as late as between plumerias. In that year, William M. Moragne Sr. became manager of Grove Farm Plantation on Kauai, which specialized in sugar cane, pineapple, and cattle. Moragne (pronounced “Mor-AY-nee”), who was born in Hilo, Hawaii, in 1905 and graduated from the University of Hawaii with a major in civil engineering and sugar technology, was an avid lover of plants and had always wanted to experiment with cross-pollinating plumerias. But because there were no books to tell him how to proceed, he had to learn on his own.

The plumeria’s pistil-the stigma, style, and ovary that are the female reproductive parts-is located at the bottom of a very deep trumpet, and efforts to tear away the petals to reach the pistil produced a torrent of sticky white latex. So Moragne snipped off the petals at the tube and allowed them to “bleed” to get rid of the latex. The pollen of the mother flower was carefully scraped away before introducing the pollen of the male parent. But after three years of effort, he failed to produce a single seed pod.

Then in 1953, reflecting on the fact that the flowers were deep throated, Moragne realized that they would have to be pollinated naturally by little bugs crawling down into the throat and climbing around the pistil. In doing so, they would leave some pollen grains under the pistil, as well as on top. Perhaps, he reasoned, he should also place pollen under the pistil. He carefully transferred pollen to the sides and base of the pistils of four blossoms through an incision cut into the side of the flower tubes. His pollinations were carried out in the morning on newly opened flowers. After the pollen was transferred, he covered the pollinated area with plastic tape to prevent uncontrolled pollen from being carried in by insects.

Several weeks later, he realized that seed pods were beginning to swell the base of the flowers he had cross-pollinated. From those seeds he obtained 283 seedlings. The thirty-five he kept produced small trees with large, brilliant, fragrant blossoms, some of which bloom for six to eight months. Moragne at first numbered the seedlings as they came into bloom-some took five years to bloom, others as long as eighteen-but then began to select the largest flowers among the more brightly colored ones to name for the women of his family.

Only three of his eleven named hybrids- ‘Jean Moragne Jr.’, named for a daughter-in-law, and ‘Edi Cooke’ and ‘Julie Cooke’, named for two of his granddaughters-have been registered with the Plumeria Society of America, which came into existence just four years before his death in 1983*. In the late 1980’s a renewed interest in plumeria led to great demand for cuttings of his hybrids at botanical garden plant sales. But as with many vegetatively propagated plants, cuttings had found there way into many gardens in Hawaii and abroad, sometimes with a name change along the way.

Now, more than forty years after he developed his series of hybrids, there is confusion about the parentage of these historic crosses. According to the Register of Plumeria Culture, the male parent is ‘Scott Pratt’ and the female parent is called ‘Daisy Wilcox’. But in a 1974 newspaper article, Moragne was quoted as saying his hybrids were a cross between ‘Grove Farm’ and an otherwise unknown ‘Koloa Red’. In trying to update the Register for the society in 1988, John P. Oliver asked for help in finding out which was right.

Although Moragne reportedly kept records relating to his breeding breakthrough, none can be located today. The answers had to be found by talking to his daughters, Mary Moragne Cooke, Sally Moragne Mist, and Katie Moragne Bartness, and a long-time plantsman on Kauai, Howard Yamamoto.

Among the plumerias in Moragne’s garden near Lihue, Kauai, was the cutting of a chance seedling originally collected from Lawaii Kai on the southern side of Kauai by plumeria enthusiast Alexander McBryde. The cutting was planted there when the plantation was still being managed by a couple named Ralph and Daisy Wilcox. Daisy Wilcox demurred at the suggestion that the flower be named for her, and Moragne-whether bowing to her wishes or simply because he preferred place names, called it ‘Grove Farm’. Nevertheless, the name ‘Daisy Wilcox’ stuck among plumeria growers on the island, and ‘Daisy Wilcox’ it became officially when plumerias began to be registered many years later. ‘Daisy Wilcox’, a large, white-flowered plumeria with a pink stripe on the underside of the petals, bears little resemblance to a plumeria now registered as ‘Grove Farm’, a grainy pink one also found on Kauai. The large flower and tree size of most of the named selections, coupled with a letter written by Moragne in 1973, leave no doubt that the ‘Grove Farm’ plant he used was the large-flowered one.

Records relating to the male parent are even more conflicting. The only place the name ‘Koloa Red’ appears is in a 1974 newspaper interview. It may have been a reporting or typographical error; no one knows. In a 1975 account, Mary Moragne Cooke related that ‘Grove Farm’ was crossed with ‘Kohala Red’; more recently, she discovered a slide dated 1955 that identifies the hybrid here father named after here as a cross of ‘Kohala’ on ‘Grove Farm’.  

There is little question that ‘Kohala Red’ is a synonym for a dark red plumeria eventually registered as ‘Scott Pratt”. Pratt was the farm manager of the Kohala Sugar Plantations on the island of Hawaii. Once again, Moragne preferred the place name.

Cuttings from the series provided by Moragne to University of Hawaii plumeria breeder Ted Chinn in 1967 carried the notation in the accession book: ‘Kohala’ on ‘Grove Farm’ or ‘Scott Pratt’ on ‘Daisy Wilcox’. Both are right, given the synonymous names for the red and the confusion over the large white. But due to the registration of plumeria names and descriptions with the Plumeria Society of America, ‘Scott Pratt’ must be listed as the male parent and ‘Daisy Wilcox’ as the female parent for the Moragne series. (This is an unrecorded marriage in the history of Hawaii’s long-time or kama’aina families, which may well support Moragne’s preference for place names.)

None of the surviving selections have the small flowers or dark red color of ‘Scott Pratt’. The strong yellows in some of them are not seen in either of the parents, but this isn’t surprising given that Moragne selected for large size and colorful petals.

More than twenty years after the crosses were made, recollections are also vague about how many flowers Moragne actually attempted to pollinate. It is well documented that he harvested seed from the pods of four flowers and from them produced 283 seedlings, naming his favorites for his wife, “Jean Sr.”; daughters Mary, Sally and Katie; daughter-in-law “Jean Jr.”; and granddaughters Cindy, Kimi, Julie, Edi, Cathy, and Kelly.

He planted fifteen around his home, and set out nine other hybrids and the rest of his breeding collection along the Nawiliwili highway that once led into Grove Farm, near the present-day Ulu Ko subdivision. The plants are not identified-Moragne removed the tags before planting them-but are still much admired, so much that many cuttings have been poached over the years.

When asked why he had not continued his pollination work, Moragne responded that with 400 potted orchids and a garden of heliconias and gingers, he didn’t have time or space for another 283 plumerias. He had selected the best and that was enough.

Today, a few of the best of the Moragne hybrids are used for leis or worn pinned in the hair or wired as nosegays. From their ‘Daisy Wilcox’ parentage, some-primarily the numbered ones-inherited a rangy growth habit, but others are more compact and suited to landscape use.

Moragne gave cuttings to Foster Garden, the University of Hawaii, And the Pacific Tropical Botanical Garden. Shortly before his death, he gave cuttings to Jim Little, a photographer and university instructor and amateur botanist whom he also taught how to hand-pollinate plumerias. Little and a few others plumeria hobbyists have kept Moragne’s legacy alive.

His hybrids represent a rare ability to choose only the best from a seedling population. It has been a long time since those initial plants were chosen, and their distribution has been limited by the isolation of the source and the lack of awareness among individual nurserymen of the uniqueness of these plants. It is time that these brilliantly colored, fragrant trees receive the recognition they deserve through more widespread propagation and use in tropical and protected subtropical landscapes.


RESOURCES & SOURCES

Jim Little Nursery & Farms, Hawaii
Richard A. Criley, University of Hawaii at Manoa
The Plumeria People, Houston, Texas
The Exotic Plumeria (Frangipani), by E. H. Thornton and S. H. Thornton, 1985
The Handbook on Plumeria Culture, by R. Eggenberger and M. H. Eggenberger, 1988


Dr. Richard A. Criley is professor of horticulture at the University of Hawaii at Manoa.  Jim Little is a retired assistant professor since 2000.  He runs one of the largest plumeria nurseries, located in Hawaii .

*The Plumeria Society of America was formed in 1979.

About The Plumeria Database

About The Plumeria Database

There is a wide variety of named plumeria cultivars, with over 400 registered varieties and more than 4,000 named ones. The Plumeria Society of America, Inc. is authorized to register plumeria varieties.

One of the challenges in accurately identifying plumerias is that they can be propagated, sold, or gifted under incorrect or made-up names. These alternative names then become associated with the proper name of a particular plumeria. This issue arises for various reasons, including variations in flower appearance when grown in different regions worldwide. Factors like sunlight, water, and fertilizer can also impact the growth habit of plumerias, further complicating their identification.

Unfortunately, some hobbyists and sellers may not prioritize properly identifying plumeria cultivars. This can lead to confusion and inconsistencies in the naming and labeling of these plants. As a result, it becomes more challenging to determine the correct name of a plumeria.

The Plumeria Society of America, Inc. and other knowledgeable plumeria enthusiasts can provide valuable guidance and expertise in identifying plumeria varieties. Their experience and understanding of the plants can help them navigate the complexities and inconsistencies associated with plumeria names and characteristics.

We’re not trying to offer everything you need to positively identify a plumeria! We are simply trying to offer you enough information to know which plumeria(s) to compare for the proper identification.

The Plumeria Database is a depository for plumeria information

A comprehensive resource managed by plumeria enthusiasts, offering standardized information about plumeria worldwide. The database includes various details such as names, species, cultivars, abstracts, characteristics, images, care information, references, and web links.

The primary objective of the Plumeria Database is to promote the characteristics of different plumeria varieties, aiding in their identification. However, it also encourages academic, educational, and general use of its information. By offering a centralized repository of plumeria-related data, the database aims to minimize name duplication and facilitate the exchange of information on an international scale.

Such a resource can be valuable not only for plumeria enthusiasts but also for researchers, educators, and anyone interested in learning more about plumeria. It serves as a platform for sharing knowledge and fostering a better understanding of these beautiful plants.

If you want to identify a particular plumeria or explore the world of plumerias, consulting the Plumeria Database can be a helpful starting point. It provides information that can assist in different aspects, from identification to care and cultivation.

Plumeria Propagation

The Plumeria Database also provides extensive information on the propagation of plumeria. Plumerias are known for their relatively easy propagation, and detailed explanations of different propagation methods can be immensely helpful for plumeria enthusiasts.

The success of propagation methods can vary depending on factors such as growing conditions, locations, and the time of year. By explaining each method in detail, the database can provide a comprehensive understanding of how and why a particular propagation method might or might not work for individuals.

Understanding the intricacies of various propagation techniques can empower plumeria growers to choose the most suitable method for their specific circumstances. Whether it’s through cuttings, grafting, or other techniques, the Plumeria Database can provide valuable insights into the best practices for successfully propagating plumeria plants.

If you are interested in propagating plumeria or expanding your knowledge on the subject, referring to the information available in the Plumeria Database would be a valuable resource.

How to keep your plumeria healthy

Maintaining your plumeria plants’ health is crucial for their success and longevity. With the abundance of information available, it can be challenging to determine what practices will work best for your specific circumstances. The Plumeria Database aims to address these concerns by providing valuable information on various aspects of plumeria care.

Proper nutrition is essential for the well-being of plumeria, and the database can offer guidance on providing them with the necessary nutrients. It may include information on soil preparation, fertilizer recommendations, and the importance of balanced nutrition for optimal growth and flowering.

Protecting plumeria from diseases and insects is another vital aspect of their care. The database can provide insights into common diseases, pests, and preventive measures to keep your plants healthy. It may cover identifying signs of diseases or pest infestations, appropriate treatments, and proactive strategies for minimizing risks.

Selecting the right plumeria for your garden is a significant consideration as well. The Plumeria Database may offer insights into different plumeria varieties, their characteristics, and suitable growing conditions. This information can help you make informed choices when adding plumerias to your garden, considering factors like climate compatibility, size, and flower characteristics.

By providing information on these and other relevant topics, the Plumeria Database aims to equip plumeria enthusiasts with the knowledge necessary to care for their plants effectively. It serves as a valuable resource for understanding the best practices and considerations for maintaining healthy and thriving plumeria plants in different gardening environments.

Plumeria Collections

The Plumeria Database has a dedicated section called “Plumeria Collections” to recognize and showcase the contributions of various growers to the plumeria community. The database acknowledges the efforts and results of these dedicated individuals by featuring descriptions and photo galleries of their plumeria introductions or hybrids.

Including historic collections like the Moragne Collection and Thornton Collection and notable growers such as Florida Colors Nursery, Jim Little Farms, and Jungle Jack Plumeria, highlight the diversity and significance of contributions to the plumeria world.

Additionally, the database aims to include collections from smaller growers, such as the Norwood Collection, Ford Collection, and Herzog Collection, recognizing that contributions come from enthusiasts at all levels.

The Plumeria Collection section is a continuous work in progress, intending to expand and add more collections in the future. This openness to including new collections and additional information reflects the collaborative and community-driven nature of the Plumeria Database.

If you have your own plumeria collection or have additional information to contribute, you are encouraged to join the effort and add your collection to the Plumeria Database. By doing so, you can contribute to the collective knowledge and appreciation of plumerias while connecting with fellow enthusiasts.

Overall, the Plumeria Collection section serves as a platform to celebrate the accomplishments of plumeria growers and fosters the exchange of information, thereby enriching the plumeria community as a whole.

All content is copyrighted in 2023 by The Plumeria Database. All photographs remain the property of the photographer.

Founding members of The Plumeria Database

Tex Norwood – On Facebook, Diana Donnellan – On Facebook
Mike Atkinson – On Facebook, Mark Wright – On Facebook

Plumeria – Frangipani Characteristics

Pumeria Characteristics

This page describes general observations and characteristics of cultivars of genus Plumeria. The plumeria genus comprises five or more species, although nearly all cultivars are considered part of species P. rubra or P. obtusa. We are concerned with the flower, the leaf, and the plant as a whole. There are certain characteristics considered when assigning to a species or in recognition of a variety. We document many of those characteristics for each variety in Cultivars and Varieties.

Growth Habit

Plumeria seems to have a fairly well-defined growth habit but will sometimes exhibit peculiar behavior. Compare plumeria to cats: they excel in doing things they are not supposed to do! Nearly every generally accepted rule of plumeria culture will, from time to time, be proven incorrect. For example, plumeria require full sun to bloom (what about the one in the garage in full bloom during the winter?); plumeria need to bloom to branch (What about this one with over 30 tips that’s only bloomed three times!)

You can propagate almost any part of a plumeria tree by cutting. See How to Grow Plumeria from a Cutting for a procedure that will usually produce successful results. Though there are other ways to propagate plumeria, the plant whose habit we are describing usually begins from a cutting, no matter how large or small.

The plumeria branch tip is where new growth, including leaves and flowers, occurs. The branch and its tip are interesting since the tip is usually the same diameter as the rest of the branch. The young branch and its tip more closely resemble a broomstick than a young tree branch. The young branch and its tip are soft but brittle, herbaceous material, full of the white milky latex plumeria sap. As new leaves are grown, the branch extends by adding tissue to the end of the tip. When an inflorescence (flower bud or stalk) is produced, the tip divides into one or more new tips that continue to grow with as much vigor as the original tip. The new tips usually grow at a predictable angle concerning the original branch tip. This is how a plumeria branches. Obviously, if it only divides into one new tip no branching has occurred. The normal branching habit, or an average number of new tips produced, is probably two or three. This process continues indefinitely, with each tip branching on the average once every year or two. The length of tip growth per year is based on various factors, including variety, growing conditions, and nutrition. Once a particular bit of plumeria branch has dropped its leaves, it will never replace them as new leaves are always produced by new growth at the tip of the branch.

The plumeria’s annual growth cycle has evolved to accommodate a dormant period to coincide with months of drought in the arid tropical regions of Mexico, Central America, and the Caribbean Islands, where it is indigenous. This corresponds to the Winter season in the Northern Hemisphere and permits storing the plant indoors, out of light, out of sight, and out of mind when outdoor weather conditions are likely to include frost or freezing temperatures. While dormant, the plumeria requires no care, and most varieties will lose all of their leaves.

As the sun’s intensity and temperatures increase during the spring, plumeria begins to break dormancy by producing leaves and an inflorescence on many tips. Many plumerias will be in full bloom before the spring rains and before producing a single leaf!

Active growth occurs after spring rains as long as temperature and sunlight requirements are met. Most vegetative growth occurs under these conditions. This includes revitalization or regeneration of a desiccated root system, new leaf growth, and stem and branch elongation. Many varieties will continue to bloom and initiate new inflorescence during the vegetative period. Most varieties will set seed pods during this period as well.

As fall approaches, drought, less sunlight, and cooler temperatures all contribute to plumeria entering its dormant period. Many lower leaves will turn yellow and drop, flowering will be significantly reduced or stop altogether, and overall plant growth will dramatically slow or come to a stop. The fully dormant plumeria’s requirements are few: temperatures above freezing and conditions on the dry side. Dormancy lasts from one to five months, depending on environmental factors.

Characteristics Overview

Flowers

Plumeria flowers have five petals, although flowers with four, six, seven, or more petals are not uncommon. Some types of flowers do not fully open and are called a shell, semi-shell, or tulip-like. Most flowers have a strong pleasant fragrance that is most intense during the early part of the day. Many different fragrances have been described, but since smell is so subjective and varies for environmental and nutritional reasons, we do not attempt to be comprehensive in its description. We try harder with colors. There seem to be several basic plumeria color schemes: white with a yellow center, yellow, multicolor, pink, and red. There is speculation that red is a special case of multicolor. Most of the reds can be more properly referred to as red-purple.

Leaves

Plumeria leaves are generally green. What a surprise! However, when examined closely, they can exhibit remarkable variation that is species and variety-dependent. We limit our leaf description to shape, color, size, and texture.

Plants

The plumeria is more appropriately considered a tree. In the tropics, it can grow to heights over thirty feet. A mature plumeria has solid hardwood and can be safely climbed by the average person so long as the limbs are at least three inches in diameter. Remember to keep your weight where the branches intersect or are sure there are plenty of cushions below!

We are concerned about the general growth habit of a plumeria variety, how well it branches (IE what is the usual number of new tips produced from a tip when it blooms), its history, its seed-bearing potential, and its use as a container, ornamental, or landscape plant.

Characteristics in Detail

Flowers

Measurements of plumeria flower varieties concern other plumerias. When a universal standard can be applied, such as a ruler or color chart, we use it; otherwise, the comparison is among peers.

    • Petal Colors: We have done our best to obtain the closest color possible using state-of-the-art desktop digital imaging hardware and software to produce the images we present.
      Please remember: ambient temperatures play a significant role in the plumeria red and red-purple pigmentation intensity. For the most part, our images were made in California and Hawaii when ambient temperatures ranged from 70°F to 90°F. In Florida and Texas, when ambient temperatures range from 80°F to near 100°F, expect the red-purple pigments to be significantly exaggerated. We will be adding more images from around the world as time permits.
    • Size: The size of the flower recorded represents an average floret. It has been stretched out to its maximum width without risking pulling it apart. The distance between the two most distant petal tips is then measured. Please be aware this average can be off by as much as 100%! A great deal depends on the plant’s maturity, environment, and the point in the flowering cycle. Many varieties will produce larger flowers early in the flowering cycle.
    • Petal Texture: This is a subjective measurement of how one variety’s flower measures up to another. When you take the measurements, we used a zero to three scale, with zero being fragile, one being delicate (typical of most plumeria), two being strong, and three being rigid. Generally, strong and rigid flowers will last longer and be somewhat better lei flowers than those described as delicate.
    • Fragrance: This is a very subjective measurement. Most plumeria enthusiasts know what a plumeria smells like. It smells like a plumeria! What a surprise! The scent is wonderful but indescribable. Sometimes we call it floral sweet, and other times we describe it as simply plumeria. When possible, we may apply additional fragrance descriptions.
    • The intensity of Fragrance: Another subjective measurement, made within the context of plumeria. We rated each variety on a zero to three scale. Zero was used to detect no fragrance, one for light to mild fragrance, two for moderate to strong, and three for heavy.
    • Tendency to Fade: When a difference is noted in the colors of older flowers compared to newer flowers on the same plant, it is usually due to bleaching by the sun’s ultraviolet rays. We refer to this effect as its tendency to fade. Fading is most apparent in the red-purple pigments but can also affect the pinks and yellows. We rated this tendency as none, slight, moderate, or dramatic.
    • Petal Type: Petals are described according to their overall shape, their tip, and any unusual characteristics they may possess. Plumeria petals fall into either ellipticalobovate, and rarely spatulate categories. They can be further described as wide or narrow. Occasionally, we find petals with other characteristics, such as reflexed or twisted. Petal tips are described as round or pointed. When we get the illustrations in place, this will be much clearer.
      • Elliptical: The widest part of the petal is close to the middle.
      • Obovate: The widest part of the petal is close to the tip.
      • Spatulate: Special case of obovate, where the petal is spoon-shaped.
      • Wide: Petal somewhat round.
      • Narrow: The petal is more than four times longer than it is wide.
      • Reflexed: The fully open petal will nearly form a semi-circle where its tip may be pointing down or back to its base. See Singapore for an example.
      • Twisted: The petal is convoluted in several ways that give a curled or even a fluted appearance. See Madame Poni or Celadine for examples of twisted and fluted.
      • Round tip: The tip does not come to a point.
      • Pointed tip: The tip comes to a point. Sometimes we use somewhat pointed where the tip appears pointed, but may also be considered rounded.
      • Flower Type: This description applies to the plumeria blossoms that fail to open or open peculiarly. Some varieties frequently will not open into a flower but remain as a partially open bud resembling some types of small spiral seashells; these are referred to as shells. Others open more fully than shells but not fully retaining a cupped or tulip-like appearance; these are referred to as semi-shells. Since most plumeria florets open fully, this description is only used for those that do not.

Leaves

The emphasis is on the flower. However, some interesting items are observable in plumeria leaves that can aid in the identification of varieties in or out of bloom.

    • Color: It should be no surprise that most plumeria leaves are described as green. There are, however, variations of green, some showing a purplish tint or even a blackening. Generally, we describe them as simply light green or green unless there is really some other aspect worthy of note.
    • Texture: A measurement of plumeria leaves usually describing how rigid the leaf is compared to other varieties of this species. Generally, we will describe the leaf as flexible or rigid depending on how easy it is bent. Consider a leaf held by its petiole (stem) being waved back and forth slowly through the air. One that shows significant distortion from its plane from air resistance is described as flexible. One that retains its shape is described as rigid. Since you can describe nearly all plumeria leaves as glabrous (smooth and not hairy (pubescent)), we only mention the rare exceptions. The bottoms of nearly all plumeria leaves are also considered glabrous, even though they are bumpy with exaggerated veins.
    • Leaf Border Color: The extreme edge of the plumeria leaf may show some color other than green, frequently red. This may be an indication of the variety’s heritage.
    • Petiole Color: The petiole is the leaf stem. It is usually green or green with a reddish tint. This may be an indication of the variety’s heritage.
    • Leaf Shape: We are concerned with the shape, size, and tip of the plumeria leaf. This may be an indication of the variety’s heritage and can aid in identification. Plumeria leaves are described as elliptic, oblanceolate, and rarely lanceolate. These descriptions can be refined as wide or narrow as necessary. The tip of the leaf is described as acuminate, acute, or obtuse.
      • Elliptic: The widest part of the leaf is near its center.
      • Oblanceolate: The widest part of the leaf is nearer its tip than its center.
      • Lanceolate: The widest part of the leaf is nearer its petiole than its center.
      • Acuminate: The curve of the leaf edge will abruptly change as it narrows near its tip.
      • Acute: The curve of the leaf edge will not significantly change as it narrows near its tip.
      • Obtuse: The leaf will have a very blunt tip that does not usually come to a point.
    • Leaf Length and Width: A typical mature leaf is measured. The measurement does not include the petiole. The width is measured at its widest point. While no studies have been performed to our knowledge, the length and width ratio may be more significant than the length and width measurements themselves.
    • Variegation: A few plumeria varieties will show light to moderate random changes in the coloration in different random areas of a single leaf. This is referred to as variegation. Since it is so unusual, it is only mentioned when observed.

Plants

Measurements and observation of the overall plumeria tree are interesting as they can relate to its suitability as an ornamental, container-grown, or landscape plant. They can also be of interest to growers for their genetic information and possible use in hybridization.

    • Pollen Parent: The name of the male parent if known.
    • Seed Parent: The name of the female parent if known.
    • Deciduous or Evergreen: Deciduous plumeria usually drop most if not all of their leaves during a dormant period. Evergreen plumeria either retain most of their leaves while dormant or do not experience an annual dormant period. In the sub-tropic climates where evergreen plumeria are stored indoors for the winter, most evergreen varieties do go dormant and do drop their leaves.
    • Seed Production: This is based on our experience, observation, and advice from others. Seed production is rated as none observed (not known to had ever set seeds), rare (once), seldom (unusual but occasional), average (at least once a year), or profuse (much more than average). Seed production relates to how a mature plumeria specimen will produce many seed pods under good conditions.
    • Branching: Based on the observation of how many new tips grow after an inflorescence is produced. For this measurement, we examine a specimen of the given variety and note how many new tips are usually produced. This frequently falls into the range of one to five to which we apply our opinion of the variety’s branching habit:
      • Poor:
      • Fair:
      • Good:
      • Excellent:
    • Growth Habit: This is a subjective description of our opinion of the plant’s stance. Growing habits are affected by environmental factors.
      • Dwarf: Refers to the shortest and most compact growing plumeria with small leaves and usually small flowers.
      • Compact: Usually a smaller plant with better branching habit and minimal stem elongation before blooming and branching again.
      • Upright: Refers to the attitude of the plant. More specifically, to the angle that new tips emerge from an old tip after blooming. The angle is the wide angle that the new tip makes concerning the original branch. When this angle is wide, the plant appears more upright. For example, if a new tip emerged at a 180° angle from the original tip, it would be in perfectly straight alignment with it—no plumeria exhibit this characteristic, except in the case where the plumeria blooms without branching. Yet, the closer this angle approaches 180°, the more upright its character is. An upright plant is considered the opposite of a rangy plant.
      • Rangy: Refers to the attitude of the plant. More specifically, to the angle that new tips emerge from an old tip after blooming. When the angle is narrow, sometimes approaching 90°, the plant takes on a rangy appearance. This characteristic is exaggerated when the new branches curve, sometimes down, before blooming and branching again. Rangy plants frequently have significant stem elongation before blooming and branching again. A rangy plant is considered the opposite of an upright plant.
      • Lanky: Usually a larger plant with more stem elongation before blooming and branching again. Normally applied to upright plants rather than rangy plants since rangy plants frequently exhibit this characteristic.
      • Dense: Refers to the relative closeness of branches to each other and can be used with other growth habits in seemingly contradictory ways such as Rangy, dense. This is a subjective opinion rather than a measurement.
      • Trunk Circumference: This measurement is taken approximately 300 cm from the ground. It is provided to indicate the relative maturity of the specimen examined.

The Standard Reference

The standard reference used is The Royal Horticultural Society Colour Chart. The society is recognized worldwide, and presumably, their color chart is available worldwide. See Obtaining the standard reference below to acquire a copy of the color chart.

Using the Standard Reference

The color chart should always be used in daylight, not in direct sunlight, but in a bright shady spot. Most plumeria reds will be found in Fan 2 in the Red-Purple Group.

Start by selecting the blossom to be examined. It should be fully opened but not so old that significant fading has occurred. Usually, this will be one or two days after it begins to open. Certain varieties will have already have begun to fade; this can not be helped. Start by tearing a single petal from a plumeria blossom. Lay the petal on a clean sheet of paper top side up and petal tip pointing to the top of the sheet. Draw its outline with a pen or pencil. Flip the petal over someplace else on the same sheet and repeat this process. Examine the petal closely, determine its significant areas of banding, striping, and differing colors. Without getting too carried away, draw those areas within the petal outlines on the sheet of paper. Many plumeria blossoms possess some of these characteristics:

  • Topside of the petal from left to right
    • Slight to pronounced curl
    • Color intensification from the left to the right side
    • Red pigment granularity decreasing from left to right
    • Stripe of color on the right side
    • Color shifting from yellow to white from base to tip
  • Bottom side of the petal from left to right
    • Stripe of color on the left
    • Subsequent bands of lessening color intensity, becoming grainy
    • The tendency for color shifting to white toward to right petal tip
    • A tiny patch of yellow or orange at the extreme right base

Using a pair of scissors, cut the petal into pieces containing only one significant color. Don’t attempt to get every graduation of color, just two or three areas of different, representative, and uniform color. Perform this process for the top and bottom of the petal.

Dealing with a single piece of a petal at a time, flip through the fan that probably contains the matching color. Use a “narrowing down” process of elimination by selecting several close matches, then finally choose the one that seems to be the best match. An exact match is a rare occurrence. Keep in mind that hue is more important than intensity. Annotate the drawing with the color chart code for that petal area. An example color chart code would be Red-Purple 61A.

After all, areas are marked, the petal is described in a narrative form incorporating the appropriate color codes. Color descriptions used in Cultivars and varieties use this technique.

Obtaining the Standard Reference

The Plumeria Place has no affiliation with the Royal Horticultural Society. This information is believed to be correct but can not be guaranteed. Given the aforementioned, the Colour Chart can be obtained by snail mail order. The cost is about $35.00 US, and it is believed Visa and Master Card are accepted. Send request and credit card information to:

RHS Enterprises
Wisley, Woking,
Surrey. GU23 6QB
England

Camelot Clone

Flower Details

Flower Width: 2 1/2″ – 3″
Texture:  Good to rigid
Tendency to Fade:  Moderate
Petal Type:  Elliptical, rounded tip
Fragrance:  Plumeria, Spicy
Intenstiy of Fragrance:  Mild

Leaf Details

Color:  Green
Texture:  Rigid
Leaf Border Color:  Red
Petiole Color:  Green
Shape:  acuminate tip
Length:  12″
Width:  6″

Tree Details

Pollen Parent:  Unknown
Seed Parent:  Penang Peach
Deciduous
Seed production: Heavy
Branching: Good
Growth habit: Broad, Compact

Plumeria.Today is grouping plumeria into Collections. Some examples are the Moragne Collection, Thornton Collection, Florida Colors, Jungle Jack and Jim Little are well known and naturals. We will also create smaller collections for the small growers who have registered plants and/or raised notable seedling. We are also grouping plumeria from different countries into Collections. 

Norwood Collection

Florida Colors Collection

United States Collection

Water Uptake and Transport in Vascular Plants

Water Uptake and Transport in Vascular Plants

By: Andrew J. McElrone (U.S. Department of Agriculture, Agricultural Research Service, University of California, Davis), Brendan Choat (University of Western Sydney), Greg A. Gambetta (University of California, Davis) & Craig R. Brodersen (University of Florida) © 2013 Nature Education 
 
Citation: McElrone, A. J., Choat, B., Gambetta, G. A. & Brodersen, C. R. (2013) Water Uptake and Transport in Vascular Plants. Nature Education Knowledge 4(5):6
 
How does water move through plants to get to the top of tall trees? Here we describe the pathways and mechanisms driving water uptake and transport through plants, and causes of flow disruption.
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Why Do Plants Need So Much Water?

Water is the most limiting abiotic (non-living) factor to plant growth and productivity, and a principal determinant of vegetation distributions worldwide. Since antiquity, humans have recognized plants’ thirst for water as evidenced by the existence of irrigation systems at the beginning of recorded history. Water’s importance to plants stems from its central role in growth and photosynthesis, and the distribution of organic and inorganic molecules. Despite this dependence, plants retain less than 5% of the water absorbed by roots for cell expansion and plant growth. The remainder passes through plants directly into the atmosphere, a process referred to as transpiration. The amount of water lost via transpiration can be incredibly high; a single irrigated corn plant growing in Kansas can use 200 L of water during a typical summer, while some large rainforest trees can use nearly 1200 L of water in a single day! 
If water is so important to plant growth and survival, then why would plants waste so much of it? The answer to this question lies in another process vital to plants — photosynthesis. To make sugars, plants must absorb carbon dioxide (CO2) from the atmosphere through small pores in their leaves called stomata (Figure 1). However, when stomata open, water is lost to the atmosphere at a prolific rate relative to the small amount of CO2 absorbed; across plant species an average of 400 water molecules are lost for each CO2 molecule gained. The balance between transpiration and photosynthesis forms an essential compromise in the existence of plants; stomata must remain open to build sugars but risk dehydration in the process.

Rendering of an open stoma on the surface of a tobacco leaf.

Figure 1: Rendering of an open stoma on the surface of a tobacco leaf.
Stomata are pores found on the leaf surface that regulate the exchange of gases between the leaf’s interior and the atmosphere. Stomatal closure is a natural response to darkness or drought as a means of conserving water.
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From the Soil into the Plant

Essentially all of the water used by land plants is absorbed from the soil by roots. A root system consists of a complex network of individual roots that vary in age along their length. Roots grow from their tips and initially produce thin and non-woody fine roots. Fine roots are the most permeable portion of a root system, and are thought to have the greatest ability to absorb water, particularly in herbaceous (i.e., non-woody) plants (McCully 1999). Fine roots can be covered by root hairs that significantly increase the absorptive surface area and improve contact between roots and the soil (Figure 2). Some plants also improve water uptake by establishing symbiotic relationships with mycorrhizal fungi, which functionally increase the total absorptive surface area of the root system.

Root hairs often form on fine roots and improve water absorption by increasing root surface area and by improving contact with the soil.

Figure 2: Root hairs often form on fine roots and improve water absorption by increasing root surface area and by improving contact with the soil.
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Roots of woody plants form bark as they age, much like the trunks of large trees. While bark formation decreases the permeability of older roots they can still absorb considerable amounts of water (MacFall et al. 1990, Chung & Kramer 1975). This is important for trees and shrubs since woody roots can constitute ~99% of the root surface in some forests (Kramer & Bullock 1966).

Roots have the amazing ability to grow away from dry sites toward wetter patches in the soil — a phenomenon called hydrotropism. Positive hydrotropism occurs when cell elongation is inhibited on the humid side of a root, while elongation on the dry side is unaffected or slightly stimulated resulting in a curvature of the root and growth toward a moist patch (Takahashi 1994). The root cap is most likely the site of hydrosensing; while the exact mechanism of hydrotropism is not known, recent work with the plant model Arabidopsis has shed some light on the mechanism at the molecular level (see Eapen et al. 2005 for more details).

Roots of many woody species have the ability to grow extensively to explore large volumes of soil. Deep roots (>5 m) are found in most environments (Canadell et al. 1996, Schenk & Jackson 2002) allowing plants to access water from permanent water sources at substantial depth (Figure 3). Roots from the Shepard’s tree (Boscia albitrunca) have been found growing at depths 68 m in the central Kalahari, while those of other woody species can spread laterally up to 50 m on one side of the plant (Schenk & Jackson 2002). Surprisingly, most arid-land plants have very shallow root systems, and the deepest roots consistently occur in climates with strong seasonal precipitation (i.e., Mediterranean and monsoonal climates).

Tree roots at significant depths accessed via caves.

Figure 4: Tree roots at significant depths accessed via caves.
Plant scientists examine: deep roots of Juniperus asheii growing at 7m depth in a cave in Austin, TX USA (left); an extensive fine root network attached to a single ~1cm diameter tap root accessing a perennial underground stream at 20m depth in a cave in central TX, USA; and twisty roots in a cave located in southwest Western Australia below a forest dominated by Eucalyptus diversicolor — roots in this cave system are commonly found from 20-60m depth.
© 2013 Nature Education Images provided by W. T. Pockman (Univ of New Mexico), A. J. McElrone, and T. M. Bleby (Univ of Western Australia). All rights reserved. View Terms of Use
 
Through the Plant into the Atmosphere
Water flows more efficiently through some parts of the plant than others. For example, water absorbed by roots must cross several cell layers before entering the specialized water transport tissue (referred to as xylem) (Figure 4). These cell layers act as a filtration system in the root and have a much greater resistance to water flow than the xylem, where transport occurs in open tubes. Imagine the difference between pushing water through numerous coffee filters versus a garden hose. The relative ease with which water moves through a part of the plant is expressed quantitatively using the following equation:

Flow = Δψ / R,

which is analogous to electron flow in an electrical circuit described by Ohm’s law equation:

i = V / R

where R is the resistance, i is the current or flow of electrons, and V is the voltage. In the plant system, Vis equivalent to the water potential difference driving flow (Δψ) and i is equivalent to the flow of water through/across a plant segment. Using these plant equivalents, the Ohm’s law analogy can be used to quantify the hydraulic conductance (i.e., the inverse of hydraulic R) of individual segments (i.e., roots, stems, leaves) or the whole plant (from soil to atmosphere).

Upon absorption by the root, water first crosses the epidermis and then makes its way toward the center of the root crossing the cortex and endodermis before arriving at the xylem (Figure 4). Along the way, water travels in cell walls (apoplastic pathway) and/or through the inside of cells (cell to cell pathway, C-C) (Steudle 2001). At the endodermis, the apoplastic pathway is blocked by a gasket-like band of suberin — a waterproof substance that seals off the route of water in the apoplast forcing water to cross via the C-C pathway. Because water must cross cell membranes (e.g., in the cortex and at apoplastic barriers), transport efficiency of the C-C pathway is affected by the activity, density, and location of water-specific protein channels embedded in cell membranes (i.e., aquaporins). Much work over the last two decades has demonstrated how aquaporins alter root hydraulic resistance and respond to abiotic stress, but their exact role in bulk water transport is yet unresolved.

Representation of the water transport pathways along the soil-plant-atmosphere continuum (SPAC).

Figure 4: Representation of the water transport pathways along the soil-plant-atmosphere continuum (SPAC).
(A) Water moves from areas of high water potential (i.e. close to zero in the soil) to low water potential (i.e., air outside the leaves). Details of the Cohesion-Tension mechanism are illustrated with the inset panels (A), where tension is generated by the evaporation of water molecules during leaf transpiration (1) and is transmitted down the continuous, cohesive water columns (2) through the xylem and out the roots to the soil (3). The pathways for water movement out of the leaf veins and through the stomata (B) and across the fine roots (C) are detailed and illustrate both symplastic and apoplastic pathways.
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Once in the xylem tissue, water moves easily over long distances in these open tubes (Figure 5). There are two kinds of conducting elements (i.e., transport tubes) found in the xylem: 1) tracheids and 2) vessels (Figure 6). Tracheids are smaller than vessels in both diameter and length, and taper at each end. Vessels consist of individual cells, or “vessel elements”, stacked end-to-end to form continuous open tubes, which are also called xylem conduits. Vessels have diameters approximately that of a human hair and lengths typically measuring about 5 cm although some plant species contain vessels as long as 10 m. Xylem conduits begin as a series of living cells but as they mature the cells commit suicide (referred to as programmed cell death), undergoing an ordered deconstruction where they lose their cellular contents and form hollow tubes. Along with the water conducting tubes, xylem tissue contains fibers which provide structural support, and living metabolically-active parenchyma cells that are important for storage of carbohydrates, maintenance of flow within a conduit (see details about embolism repair below), and radial transport of water and solutes.

Three dimensional reconstructions of xylem imaged at the Ghent microCT facility.

Figure 5: Three dimensional reconstructions of xylem imaged at the Ghent microCT facility.
Differences in xylem structure and conduit distributions can be seen between Ulmus americana (left) and Fraxinus americana (right) xylem.
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When water reaches the end of a conduit or passes laterally to an adjacent one, it must cross through pits in the conduit cell walls (Figure 6). Bordered pits are cavities in the thick secondary cell walls of both vessels and tracheids that are essential components in the water-transport system of higher plants. The pit membrane, consisting of a modified primary cell wall and middle lamella, lies at the center of each pit, and allows water to pass between xylem conduits while limiting the spread of air bubbles (i.e., embolism) and xylem-dwelling pathogens. Thus, pit membranes function as safety valves in the plant water transport system. Averaged across a wide range of species, pits account for >50% of total xylem hydraulic resistance. The structure of pits varies dramatically across species, with large differences evident in the amount of conduit wall area covered by pits, and in the porosity and thickness of pit membranes (Figure 6).

Comparison of different types of wood from flowering and cone-bearing plants.

Figure 6: Comparison of different types of wood from flowering and cone-bearing plants.
This features wider conduits from flowering plants (top), a cartoon reconstruction of vessels, tracheids and their pit membranes (middle), which are also shown in SEM images (bottom).
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After traveling from the roots to stems through the xylem, water enters leaves via petiole (i.e., the leaf stalk) xylem that branches off from that in the stem. Petiole xylem leads into the mid-rib (the main thick vein in leaves), which then branch into progressively smaller veins that contain tracheids (Figure 7) and are embedded in the leaf mesophyll. In dicots, minor veins account for the vast majority of total vein length, and the bulk of transpired water is drawn out of minor veins (Sack & Holbrook 2006, Sack & Tyree 2005). Vein arrangement, density, and redundancy are important for distributing water evenly across a leaf, and may buffer the delivery system against damage (i.e., disease lesions, herbivory, air bubble spread). Once water leaves the xylem, it moves across the bundle sheath cells surrounding the veins. It is still unclear the exact path water follows once it passes out of the xylem through the bundle sheath cells and into the mesophyll cells, but is likely dominated by the apoplastic pathway during transpiration (Sack & Holbrook 2005).

An example of a venation pattern to illustrate the hydraulic pathway from petiole xylem into the leaf cells and out the stomata.

Figure 7: An example of a venation pattern to illustrate the hydraulic pathway from petiole xylem into the leaf cells and out the stomata.
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Mechanism Driving Water Movement in Plants

Unlike animals, plants lack a metabolically active pump like the heart to move fluid in their vascular system. Instead, water movement is passively driven by pressure and chemical potential gradients. The bulk of water absorbed and transported through plants is moved by negative pressure generated by the evaporation of water from the leaves (i.e., transpiration) — this process is commonly referred to as the Cohesion-Tension (C-T) mechanism. This system is able to function because water is “cohesive” — it sticks to itself through forces generated by hydrogen bonding. These hydrogen bonds allow water columns in the plant to sustain substantial tension (up to 30 MPa when water is contained in the minute capillaries found in plants), and helps explain how water can be transported to tree canopies 100 m above the soil surface. The tension part of the C-T mechanism is generated by transpiration. Evaporation inside the leaves occurs predominantly from damp cell wall surfaces surrounded by a network of air spaces. Menisci form at this air-water interface (Figure 4), where apoplastic water contained in the cell wall capillaries is exposed to the air of the sub-stomatal cavity. Driven by the sun’s energy to break the hydrogen bonds between molecules, water evaporates from menisci, and the surface tension at this interface pulls water molecules to replace those lost to evaporation. This force is transmitted along the continuous water columns down to the roots, where it causes an influx of water from the soil. Scientists call the continuous water transport pathway the Soil Plant Atmosphere Continuum (SPAC).

Stephen Hales was the first to suggest that water flow in plants is governed by the C-T mechanism; in his 1727 book Hales states “for without perspiration the [water] must stagnate, notwithstanding the sap-vessels are so curiously adapted by their exceeding fineness, to raise [water] to great heights, in a reciprocal proportion to their very minute diameters.” More recently, an evaporative flow system based on negative pressure has been reproduced in the lab for the first time by a ‘synthetic tree’ (Wheeler & Stroock 2008).

When solute movement is restricted relative to the movement of water (i.e., across semipermeable cell membranes) water moves according to its chemical potential (i.e., the energy state of water) by osmosis — the diffusion of water. Osmosis plays a central role in the movement of water between cells and various compartments within plants. In the absence of transpiration, osmotic forces dominate the movement of water into roots. This manifests as root pressure and guttation — a process commonly seen in lawn grass, where water droplets form at leaf margins in the morning after conditions of low evaporation. Root pressure results when solutes accumulate to a greater concentration in root xylem than other root tissues. The resultant chemical potential gradient drives water influx across the root and into the xylem. No root pressure exists in rapidly transpiring plants, but it has been suggested that in some species root pressure can play a central role in the refilling of non-functional xylem conduits particularly after winter (see an alternative method of refilling described below).

 

Disruption of Water Movement

Water transport can be disrupted at many points along the SPAC resulting from both biotic and abiotic factors (Figure 8). Root pathogens (both bacteria and fungi) can destroy the absorptive surface area in the soil, and similarly foliar pathogens can eliminate evaporative leaf surfaces, alter stomatal function, or disrupt the integrity of the cuticle. Other organisms (i.e., insects and nematodes) can cause similar disruption of above and below ground plant parts involved in water transport. Biotic factors responsible for ceasing flow in xylem conduits include: pathogenic organisms and their by-products that plug conduits (Figure 8); plant-derived gels and gums produced in response to pathogen invasion; and tyloses, which are outgrowths produced by living plant cells surrounding a vessel to seal it off after wounding or pathogen invasion (Figure 8).

Sources of dysfunction in the xylem.

Figure 8: Sources of dysfunction in the xylem.
Left to right: (A) xylem-dwelling pathogens like Xylella fastidiosa bacteria; (B) tyloses (plant-derived); (C and D) conduit (in blue) implosion (Brodribb and Holbrook 2005, Pine needle tracheids); and (E) embolized conduits among water filled ones in a frozen plant samples (Choat unpublished figure, Cryo SEM).
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Abiotic factors can be equally disruptive to flow at various points along the water transport pathway. During drought, roots shrink and lose contact with water adhering to soil particles — a process that can also be beneficial by limiting water loss by roots to drying soils (i.e., water can flow in reverse and leak out of roots being pulled by drying soil). Under severe plant dehydration, some pine needle conduits can actually collapse as the xylem tensions increase (Figure 8).

Water moving through plants is considered meta-stable because at a certain point the water column breaks when tension becomes excessive — a phenomenon referred to as cavitation. After cavitation occurs, a gas bubble (i.e., embolism) can form and fill the conduit, effectively blocking water movement. Both sub-zero temperatures and drought can cause embolisms. Freezing can induce embolism because air is forced out of solution when liquid water turns to ice. Drought also induces embolism because as plants become drier tension in the water column increases. There is a critical point where the tension exceeds the pressure required to pull air from an empty conduit to a filled conduit across a pit membrane — this aspiration is known as air seeding (Figure 9). An air seed creates a void in the water, and the tension causes the void to expand and break the continuous column. Air seeding thresholds are set by the maximum pore diameter found in the pit membranes of a given conduit.

Air seeding mechanism.

Figure 9: Air seeding mechanism.
Demonstrates how increasing tension in a functional water filled vessel eventually reaches a threshold where an air seed is pulled across a pit membrane from an embolized conduit. Air is seeded into the functional conduit only after the threshold pressure is reached.
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Fixing the Problem

Failure to re-establish flow in embolized conduits reduces hydraulic capacity, limits photosynthesis, and results in plant death in extreme cases. Plants can cope with emboli by diverting water around blockages via pits connecting adjacent functional conduits, and by growing new xylem to replace lost hydraulic capacity. Some plants possess the ability to repair breaks in the water columns, but the details of this process in xylem under tension have remained unclear for decades. Brodersen et al. (2010) recently visualized and quantified the refilling process in live grapevines (Vitis vinifera L.) using high resolution x-ray computed tomography (a type of CAT scan) (Figure 10). Successful vessel refilling was dependent on water influx from living cells surrounding the xylem conduits, where individual water droplets expanded over time, filled vessels, and forced the dissolution of entrapped gas. The capacity of different plants to repair compromised xylem vessels and the mechanisms controlling these repairs are currently being investigated.

Embolism repair documented in grapevines (<i>Vitis vinifera</i> L.) with X-ray micro-CT at the ALS facility at Lawrence Berkeley National Lab CA, USA.”></p>
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Figure 10: Embolism repair documented in grapevines (Vitis vinifera L.) with X-ray micro-CT at the ALS facility at Lawrence Berkeley National Lab CA, USA.
(A) Longitudinal section showing a time series of cavitated vessels refilling in less than 4 hrs; (B) 3D reconstruction of four vessel lumen with water droplets forming on the vessel walls and growing over time to completely fill the embolized conduit.
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References and Recommended Reading


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Beerling, D. J. & Franks, P. J. Plant science: The hidden cost of transpiration. Nature 464, 495-496 (2010).

Brodersen, C. R. et al. The dynamics of embolism repair in xylem: In vivo visualizations using high-resolution computed tomography Plant Physiology 154, 1088-1095 (2010).

Brodribb, T. J. & Holbrook, N. M. Water stress deforms tracheids peripheral to the leaf vein of a tropical conifer. Plant Physiology 137, 1139-1146 (2005)

Canadell, J. et al. Maximum rooting depth of vegetation types at the global scale. Oecologia 108, 583-595 (1996).

Choat, B., Cobb, A. R. & Jansen, S. Structure and function of bordered pits: New discoveries and impacts on whole-plant hydraulic function. New Phytologist 177, 608-626 (2008).

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Eapen, D. et al. Hydrotropism: Root growth responses to water. Trends in Plant Science 10, 44-50 (2005).

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Holbrook, N. M. & Zwieniecki, M. A. Vascular Transport in Plants. San Diego, CA: Elsevier Academic Press, 2005.

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Kramer, P. J. & Boyer, J. S. Water Relations of Plants and Soils. New York, NY: Academic Press, 1995.

Kramer, P. J. & Bullock, H. C. Seasonal variations in the proportions of suberized and unsuberized roots of trees in relation to the absorption of water. American Journal of Botany 53, 200-204 (1966).

MacFall, J. S., Johnson, G. A. & Kramer, P. J. Observation of a water-depletion region surrounding loblolly pine roots by magnetic resonance imaging. Proceedings of the National Academy of Sciences of the United States of America 87, 1203-1207 (1990).

McCully, M. E. Roots in Soil: Unearthing the complexities of roots and their rhizospheres. Annual Review of Plant Physiology and Plant Molecular Biology 50, 695-718 (1999).

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Steudle, E. The cohesion-tension mechanism and the acquisition of water by plants roots. Annual Review of Plant Physiological and Molecular Biology 52, 847-875 (2001).

Steudle, E. Transport of water in plants. Environmental Control in Biology 40, 29-37 (2002).

Takahashi, H. Hydrotropism and its interaction with gravitropism in roots. Plant Soil 165, 301-308 (1994).

Tyree, M. T. & Ewers, F. W. The hydraulic architecture of trees and other woody plants. New Phytologist119, 345-360 (1991).

Tyree, M. T. & Sperry, J. S. Vulnerability of xylem to cavitation and embolism. Annual Review of Plant Physiology and Molecular Biology 40, 19-38 (1989).

Tyree, M. T. & Zimmerman, M. H. Xylem Structure and the Ascent of Sap. 2nd ed. New York, NY: Springer-Verlag, 2002.

Tyree, M. T. & Ewers, F. The hydraulic architecture of trees and other woody plants. New Phytologist 119, 345-360 (1991).

Wheeler, T. D. & Stroock, A. D. The transpiration of water at negative pressures in a synthetic tree. Nature 455, 208-212 (2008).

Wullschleger, S. D., Meinzer, F. C. & Vertessy, R. A. A review of whole-plant water use studies in trees. Tree Physiology 18, 499-512 (1998).

Zimmerman, M. H. Xylem Structure and the Ascent of Sap. 1st ed. Berlin, Germany: Springer-Verlag, 1983.