Chapter 11
Plants

Plants belong to the Plantae kingdom. Biologists estimate that there are up to 350,000 species making up this kingdom. In general, there are two types of land-growing plants—vascular and nonvascular. Vascular plants have specially developed organs similar to veins that move liquids through their systems. This category includes the trees, shrubs, flowers, and grasses. Nonvascular plants are mosses, liverworts, and hornworts. The vast majority of plant species on Earth are vascular plants that reproduce through their flowers.

In science, plants are more often identified by their scientific names than are animals. Plant species are so abundant and diverse that many plants have multiple common names. On the other hand, there are plants that have no common names because they are rare or geographically remote. To avoid confusion, this chapter will include the scientific name for any specific common name given.

Many factors contribute to the endangerment of plant species. Numerous species are the victims of habitat loss due to land and agricultural development. Others have declined due to pollution or habitat damage, or as a result of competition with invasive species. Still others have succumbed to introduced or unknown plant diseases. Finally, collectors or dealers often illegally seek rare, showy, or unusual plants, and have depleted populations through over-collection.

The preservation of plant species is important for many reasons. Not only are plants of aesthetic value, they are crucial components of every ecosystem on earth. Plants also serve several functions directly beneficial to humans. First, they provide genetic variation that is used in the breeding of new crop varieties—native plants provide genes that allow for adaptation to local environments, as well as resistance to pests, disease, or drought. In addition, plants are the source of numerous human medicines.

THE AMERICAN CHESTNUT TREE—MAKING A COMEBACK?

During the 1800s the American chestnut (Castanea dentate) was the predominant tree of many forests in the eastern United States. Its range extended from Maine to Mississippi, as shown in Figure 11.1. The heaviest concentrations were in the southern Appalachian Mountains where the tree made up more than a third of the overstory trees (the topmost layer of foliage in a forest). Mature trees reached three to five feet in diameter and rose to ninety feet in height with a huge canopy. The species was fast-growing and produced light, durable wood that was extremely popular for firewood and for making furniture, shingles, caskets, telephone poles, railroad ties, and other products. The trees were also valued for their chestnuts and tannin content. Tannin is an extract used in the leather industry.

In 1904 observers in New York City reported that an unknown blight (disease) was killing American chestnut trees at the Bronx Zoo. By 1940 the blight had spread through the entire range of the species, leaving all of the trees dead or dying. The tree structure was not damaged by the disease, so harvesting continued of dead trees for several more decades. Although sprouts would grow from the stumps left behind, they eventually succumbed to the blight. By the 1970s the American chestnut had been virtually eliminated. More than three billion trees had been killed. The culprit was a fungus originally called Endothia parasitica, but later renamed Cryphonectria parasitica. Scientists believe the disease came into the United States with ornamental chestnut trees imported from Japan or China. The Asian trees could carry the disease, but not succumb to it, because of natural immunity.

During the 1920s frantic efforts began to cross the remaining American chestnut trees with the Asiatic species. Although hybrid trees resulted with some resistance to the blight, they were inferior in quality to the original American species. Advances in genetic research and forestry techniques led to better hybrids by the 1980s. As of 2006 research continues by two foundations—the American Chestnut Foundation (a nonprofit organization headquartered in Vermont) and the American Chestnut Cooperators' Foundation (ACCF) at Virginia Tech University. The American Chestnut Foundation focuses on crossing naturally blight-resistant Asiatic species with American species. The ACCF produces crosses between American chestnut trees found to have some resistance to the blight in hopes of eventually producing offspring with higher resistance. Both organizations are confident that vigorous blight-resistant American chestnut trees can be developed during the twenty-first century.

PROTECTION OF PLANTS UNDER THE ENDANGERED SPECIES ACT

The Endangered Species Act of 1973 (ESA) protects listed plants from deliberate destruction or vandalism. Plants also receive protection under the consultation requirements of the act—that is, all federal agencies must consult with the U.S. Fish and Wildlife Service (FWS) to determine how best to conserve species as well as to ensure that no issued permits will jeopardize listed species or harm their habitats.

However, many conservationists believe that plants receive less protection than animals under the Endangered Species Act. First, the ESA only protects plants that are found on federal lands. It imposes no restrictions on private landowners whose property is home to endangered plants. Critics also complain that the Fish and Wildlife Service has been slow to list plant species and that damage to plant habitats is not addressed with the same seriousness as for animal species. However, the agency points out that the number of plants listed under the ESA has risen dramatically over the past two decades, as shown in Figure 11.2.

In 2000, in an effort to bolster conservation efforts for plants, the FWS formed an agreement with the Center for Plant Conservation, a national association of botanical gardens and arboreta. The two organizations are cooperating in developing conservation measures to help save North American plant species, particularly those listed as threatened or endangered. Central to the effort is the creation of educational programs aimed at informing the public about the importance of plant species for aesthetic, economic, biological, and medical reasons. The Center for Plant Conservation also aids in developing recovery plans for listed plant species.

THREATENED AND ENDANGERED U.S. PLANT SPECIES

Table 11.1 shows the 745 U.S. plant species listed under the Endangered Species Act as of March 2006. The vast majority of the plants (80%) have endangered status, while the other 20% are threatened. Nearly all of the plants have recovery plans in place. Because several species of imperiled plants are often found in the same ecosystem, many recovery plans cover multiple plant species.

The U.S. Fish and Wildlife Service uses four broad categories for plant types—conifers and cycads, ferns and allies, lichens, and flowering plants. A breakdown of listings by type is as follows:

• Conifers and cycads—three species
• Ferns and allies—twenty-six species
• Lichens—two species
• Flowering plants—714 species

Because the status of most plant species has not been studied in detail, many more plants are probably in danger of extinction than appear on these lists.

Just over $21 million was spent under the Endangered Species Act on threatened and endangered plants during fiscal year 2004. The ten plants with the highest expenditures are listed in Table 11.2. Flowering plants accounted for 97% of the total expenditures. Although plants comprise a slight majority of the total number of species listed under the ESA, they receive far less funding than animal species. Expenditures for plant species during fiscal year 2004 amounted to less than 2% of the total $1.4 billion spent that year.

PLANT TAXONOMY AND CATEGORIZATION

Taxonomy of plant species can be very complicated and is plagued by disagreements among scientists. Historically, plants were categorized by morphology—physical characteristics, such as shape or color of their leaves, fruit, bark, etc. During the 1960s a new classification scheme emerged that groups plants based on their evolutionary similarities—for example, their chemical properties and reproductive mechanisms. This taxonomy is part of the broader science known as phylogenetic systematics, which studies the evolutionary relationships between living organisms. In the future the systematics approach is expected to be used to classify all life forms.

In general, plants are assigned to the same taxonomic levels used to classify animals. This hierarchical structure includes kingdom, phylum, class, order, family, genus, and species. Beneath the species level, plants can be classified as to subspecies, just as in animal taxonomy. There is an additional classification for plants at this level called variety (abbreviated as "var."). Varieties are subgroups with unique differences between them. For example, the invasive species known as kudzu has the scientific name Pueraria montana. There are two varieties—Pueraria montana var. lobata and Pueraria montana var. montana. The lobata variety is commonly found in the United States, while the montana variety is not. Note that variety names are not italicized.

Plant taxonomy also includes additional taxa (groups) between kingdom and phylum called subkingdom, superdivision, and division that distinguish between broad categories of plants. The subkingdom level distinguishes between vascular and nonvascular plants. Within vascular plants, there are two superdivisions—seed plants and seedless plants. Seed plants are divided into various divisions, the largest of which is flowering plants.

The categories used by the FWS in Table 11.1 to categorize endangered and threatened plants are division levels or similar groupings.

Conifers and Cycads

Conifers are cone-bearing, woody plants. Most are trees; only a few species are shrubs. Common tree types include pine, cedar, fir, spruce, redwood, and cypress. As shown in Table 11.1, there are only two conifers listed under the Endangered Species Act. The Santa Cruz cypress (Cupressus abramsiana) and gowen cypress (Cupressus goveniana) are found only in Southern California. Both species are imperiled because they have

limited range of distribution and are threatened by alteration and loss of habitat.

Cycads are unusual plants often mistaken for palms or ferns. They have thick, soft trunks and large, leaf-like crowns. Cycads are found in tropical or semitropical regions. Their rarity makes them popular with collectors. The Florida torreya (Torreya taxifolia) is the only cycad listed under the ESA. This scrubby tree is extremely rare and is found only on the bluffs along the Apalachicola River in the panhandle of Florida. An unknown disease virtually wiped out the species in the wild during the 1950s.

Ferns and Allies

Ferns are an abundant and diverse plant group. There are up to 20,000 species of ferns, and they are associated mostly with tropical and subtropical regions. In general these plants are characterized by stems with long protruding "leaves" called fronds. Fern allies are plants with similar life cycles to ferns, but without their stem or leaf structure. Examples of fern allies include the club mosses and horsetails.

There are twenty-six fern and allied species listed under the ESA. Nearly all are endangered. Geographical locations with large numbers of imperiled ferns include Hawaii (twelve species) and Puerto Rico (eight species). The remaining species are found primarily in the Southeast, with the exception of the Aleutian shield fern (Polystichum aleuticum), which is native to Alaska.

Lichens

Lichens are not truly plants. Scientists place them in the fungi kingdom, instead of the plant kingdom. Lichens are plantlike life-forms composed of two separate organ-isms—a fungus and an alga. Biologists believe there are up to 4,000 lichen species in the United States. They are found in many different habitats and grow extremely slowly. Some lichens look like moss, while others appear more like traditional plants with a leafy or blade structure. Lichens do not have a "skin" to protect them from the atmosphere. They are highly sensitive to air contaminants and have disappeared from many urban areas, presumably because of air pollution. Lichens are most predominant in undisturbed forests, bogs, and wetlands, particularly in California, Hawaii, Florida, the Pacific Northwest, and the Appalachians. They are commonly found on rocky outcroppings. Lichens provide a foodstuff for some animals and are used by some bird species in nest building.

As of March 2006 there were two lichen species listed under the ESA—rock gnome lichen (Gymnoderma lineare) and Florida perforate cladonia (Cladonia perforata). Both are classified as endangered. During the 1970s rock gnome lichen was virtually wiped out in the Great Smoky Mountains National Park in Tennessee due to zealous collecting by scientists. Florida perforate clado-nia is found only in rosemary scrub habitats in portions of Florida. It is endangered due to loss or degradation of those habitats.

Flowering Plants

Flowering plants are vascular plants with flowers—clusters of specialized leaves that participate in reproduction. The flowers of some species are large and colorful, while others are extremely small and barely noticeable to humans. Biologists estimate that 80% to 90% of all plants on Earth are flowering plants.

As shown in Table 11.1, there are more than 700 flowering plants listed as endangered or threatened under the ESA. They come from a wide variety of taxonomic groups and are found in many different habitats. The five largest families represented are as follows:

• Asteraceae (asters, daisies, and sunflowers)—eighty-six species
• Campanulaceae (bellflowers)—forty-nine species
• Fabaceae (legumes and pulses)—forty-nine species
• Lamiaceae (mints)—thirty-five species
• Brassicaceae (mustard and cabbage)—thirty-four species

GEOGRAPHICAL BREAKDOWN OF PLANTS

Most threatened and endangered plant species in the United States are concentrated in specific areas of the country. Figure 11.3 shows a breakdown of listed plants by predominant region as of March 2006. More than one-third of all listings occur in Hawaii. California is home to nearly one-fourth of all listed plants. Together these two states account for more than half of all plants listed under the Endangered Species Act. One other specific region, the Southeast, is notable for its contingent (14%) of threatened and endangered plants. The majority of the imperiled plants in this region are found in Florida. The southwestern United States and Puerto Rico are each home to 7% of listed plants. The remaining 15% of imperiled plants are scattered across other regions of the country.

Hawaiian Plants

Figure 11.4 shows the eight major islands comprising the state of Hawaii. The island of Oahu is home to the state's capital, Honolulu. However, Oahu is not the largest of the islands. That distinction goes to the island labeled "Hawaii," which is commonly called "the big island." In the following discussion, the term Hawaii refers to the entire state.

Because of its isolation from continental land masses, many of the species found in Hawaii exist nowhere else in the world. An estimated 90% of Hawaiian plant species are in fact endemic. Because of large-scale deforestation and habitat destruction on the islands, Hawaii is home to more threatened and endangered plants than any other state in the nation. The U.S. Fish and Wildlife Service (2006, http://www.fws.gov/pacificislands/wesa/endspindex.html) reports that in 2006 there are 273 listed species in Hawaii. Hawaiian plants have suffered from the introduction of invasive predators such as cows, pigs, and insects, as well as the loss of critical pollinators with the decline of numerous species of native birds and insects. According to Marie M. Bruegemann in "A Plan for Hawaiian Plants and Their Ecosytems" (Endangered Species Bulletin, July-December 2003), 100 of Hawaii's 1,500 known plant species are believed to have become extinct since the islands were colonized by humans.

The U.S. Fish and Wildlife Service has developed more than a dozen recovery plans for imperiled Hawaiian plants. Many of the plans cover multiple species found in the same ecosystem or habitat types. Examples include:

• Oahu plants—sixty-six species
• Kauai plant cluster—thirty-seven species
• Waianae plant cluster—thirty-one species
• Multi-island plants—twenty-six species
• Big Island plant cluster—twenty-two species

In 2003 the FWS designated over 208,000 acres of critical habitat on the Big Island as habitat for forty-one listed plant species. The area designated was 52% smaller than originally anticipated because it excluded a large tract of U.S. Army land as well as private land held by the Queen Liliuokalani Trust and others. The U.S. Army land was excluded because of national security concerns and also because the Army agreed to voluntarily cooperate with the FWS regarding activity that affects endangered species. The Queen Liliuokalani Trust land was excluded because the trust vowed to discontinue its current efforts on behalf of endangered species if its lands were included in the critical habitat designation. Finally, land near the cities of Kailua and Kona, for which housing development was planned, was excluded from critical habitat designation because the economic and social costs of inclusion were too great.

Designation of critical habitat in Hawaii was completed after a successful lawsuit brought against the Fish and Wildlife Service by Earthjustice, the Conservation Council for Hawaii, the Sierra Club, and the Hawaii Botanical Society.

Californian Plants

As shown in Figure 11.3 California is home to 22% of threatened and endangered plant species in the United States. More than 160 imperiled plants are found there, including several types of checker-mallow, dudleya, evening primrose, grass, jewelflower, larkspur, manzanita, milk-vetch, paintbrush, rock-cress, spineflower, and thistle.

MILK-VETCH

Milk-vetch is an herbaceous perennial flowering plant found in various parts of the world. It received its common name during the 1500s thanks to a belief among European farmers that the plant increased the milk yield of goats. As of March 2006 there were ten species of milk-vetch listed as threatened or endangered in California, the most listings for any single plant type in that state. These species are as follows:

• Braunton's milk-vetch (Astragalus brauntonii)
• Clara Hunt's milk-vetch (Astragalus clarianus)
• Coachella Valley milk-vetch (Astragalus lentiginosus var. coachellae)
• Coastal dunes milk-vetch (Astragalus tener var. titi)
• Cushenbury milk-vetch (Astragalus albens)
• Fish Slough milk-vetch (Astragalus lentiginosus var. piscinensis)
• Lane Mountain milk-vetch (Astragalus jaegerianus)
• Peirson's milk-vetch (Astragalus magdalenae var. peirsonii)
• Triple-ribbed milk-vetch (Astragalus tricarinatus)
• Ventura Marsh milk-vetch (Astragalus pycnostachyus var. lanosissimus)

Peirson's milk-vetch is a plant with a long history of litigation and controversy in California. It is found in only one small area of Imperial County in the southern part of the state. (See Figure 11.5.) This area is the Imperial Sand Dunes Recreation Area (ISDRA) managed by the Bureau of Land Management under the U.S. Department of the Interior. ISDRA has a remote and barren landscape dominated by huge rolling sand dunes—the Algodones Dunes, the largest sand dune fields in North America. ISDRA covers 185,000 acres and is a popular destination for off-highway vehicle (OHV) riders, receiving more than one million visitors annually.

In 1998 Peirson's milk-vetch was designated a threatened species by the U.S. Fish and Wildlife Service because of the threat of destruction by OHVs and other recreational activities at Imperial Sand Dunes Recreation Area. The agency decided not to designate critical habitat at that time, fearing the remaining plants would be subject to deliberate vandalism. The Bureau of Land Management was sued by conservation groups and accused of not consulting with the FWS about the threats to the Peirson's milk-vetch before establishing a management plan for the Recreation Area. In 2000, in response to that lawsuit, the Bureau of Land Management closed more than a third of the ISDRA to off-highway vehicle use.

In October 2001 a petition to delist the species was submitted on behalf of the American Sand Association, San Diego Off-Road Coalition, and Off-Road Business Association. A month later two lawsuits were filed against the Fish and Wildlife Service by conservation organizations challenging the agency's decision not to designate critical habitat for the species. Under court order, the FWS proposed critical habitat in 2003. Meanwhile the delisting petition submitted in 2001 triggered a status review.

In 2004 the FWS issued a final designation of critical habitat for Peirson's milk-vetch that encompassed nearly 22,000 acres of Imperial Sand Dunes Recreation Area. This was less than half of the acreage originally proposed. The reduction was made after an economic analysis revealed that closure of ISDRA areas to off-road vehicle use would have a negative impact on local businesses. That same year the agency completed the status review triggered by the 2001 delisting proposal and found that the species should remain listed as threatened. In July 2005 the original petitioners and additional OHV and motorcycle associations submitted a new petition to delist Peirson's milk-vetch. This petition also triggered a status review, which was expected to be completed in late 2006. In a public statement, the U.S. Fish and Wildlife Service noted that the new petition contains data indicating that the species is more abundant and widespread than originally believed.

As of spring 2006 portions of the ISDRA remained under temporary closure to off-highway vehicle riders due to ongoing litigation against the Bureau of Land Management regarding management of the Recreation Area.

LOS ANGELES BASIN MOUNTAIN PLANTS

Numerous species of threatened and endangered plants have reached their precarious state due to urbanization and other human activity. Figure 11.6 shows the species distribution of six threatened and endangered plant species found in the mountains surrounding the Los Angeles basin:

• Braunton's milk-vetch (Astragalus brauntonii)
• Marcescent dudleya (Dudleya cymosa ssp. marces-cens)
• Santa Monica Mountains dudleya (Dudleya cymosa ssp. ovatifolia)
• Conejo dudleya (Dudleya abramsii ssp. parva)
• Verity's dudleya (Dudleya verityi)
• Lyon's pentachaeta (Pentachaeata lyonii)

The recovery plan for these species cites threats including "urban development, recreational activities, alteration of fire cycles through fire suppression and pre-suppression (fuel modification) activities, over-collecting, habitat fragmentation and degradation, and competition from invasive weeds." Some species are currently so reduced in number that extinction due to random events is also a threat.

Floridian Plants

As shown in Figure 11.3, the southeastern states contain 14% of the threatened and endangered plant species listed under the ESA as of March 2006. Approximately half of these listed plants are found only in Florida. They include multiple species of mint, pawpaw, rosemary, and spurge.

Many of Florida's imperiled plants are found in the southern part of the state—the only subtropical ecological habitat in the continental United States. Figure 3.2 in Chapter 3 shows a map of the south Florida ecosystem, including its national parks, national preserves, and numerous national wildlife refuges. The Fish and Wildlife Service maintains a field office in this area in Vero Beach, Florida. The majority of native plant species located in the bottom half of the south Florida ecosystem originated from the tropics.

In 1999 the FWS published the South Florida Multi-Species Recovery Plan (MSRP) covering sixty-six species, including dozens of plant species. In 2004 an implementation schedule for many of the species in the plan was issued, which divided the ecosystem into ecological communities as follows:

• Florida scrub/scrubby flatwoods/scrubby high pine—nineteen plant species
• Pine rocklands—five plant species
• Beach dune/coastal strand—one plant species
• Tropical hardwood hammock—one plant species
• Mesic and hydric pine flatwoods—one plant species
• Freshwater marsh/wet prairie—one plant species

The recovery and restoration tasks outlined in the MSRP are to be implemented through creation of a team of federal, state, and local governmental agencies; Native American tribal governments; academic representatives; industry representatives; and members of the private sector. The schedule prioritizes the plan's recovery actions and estimates costs on an annual basis for implementing the actions in each ecological community.

The South Florida Multi-Species Recovery Plan is considered a landmark plan, because it was one of the first recovery plans to focus on an ecosystem approach to recovery, rather than a species-by-species approach.

THREATENED AND ENDANGERED FOREIGN SPECIES OF PLANTS

As of March 2006 the U.S. Fish and Wildlife Service listed only three foreign species of plants as threatened or endangered as follows:

• Guatemalan pinabete fir (Abies guatemalensis)—Threatened
• Chilean false larch (Fitzroya cupressoides)—Threatened
• Coast Rican jatropha (Jatropha costaricensis)—Endangered

The 1997 IUCN Red List of Threatened Plants from the World Conservation Union (IUCN) was the first global assessment of plants, and was the result of over twenty years of study by botanists, conservation organizations, botanical gardens, and museums around the world. It revealed that 12.5%—one of every eight—of the world's plant species are in danger of extinction. In the United States, the figure is even higher, with 29% of the nation's 16,000 plant species threatened.

The IUCN also reported that the vast majority of plants at risk are extremely limited geographically; most are not found outside of their home nations, making these species particularly vulnerable to extinction. Many plant species known to have medicinal value are threatened, including many species in the yew family, a source of cancer-fighting compounds. The IUCN notes that the loss of each species causes a loss of genetic material that could be used to produce stronger, healthier crops for human and animal consumption.

The 2004 IUCN Red List of Threatened Species currently lists 8,321 species of threatened plants. This is 70% of the 11,824 plants that have been examined. However, only 4% of plant species have been studied in sufficient detail to assess their status, and the actual number of threatened species is likely to be much higher.

The majority of IUCN-listed species are flowering plants, a diverse and well-studied group. In 2004 the IUCN reported that 7,796 flowering plants were threatened. Other IUCN-listed species include eighty true mosses, 140 ferns and allies, and 305 cycads. Habitat loss accounts at least in part for the threatened status of the vast majority of IUCN-listed plants

PLANTS

Research into the flora mentioned in the ancient Hebrew literature is grounded on the basic assumption that within historical times no fundamental changes have taken place in the country's climate (see *Agriculture). This assumption, which allows conclusions to be drawn from present-day plants about the floral landscape of bygone days, is particularly important for identifying the flora of the Bible and of talmudic literature. The overwhelming majority of them can be identified with those of today, but, as with all the terms of biblical and talmudic realia, many and varied identifications and interpretations have been suggested for them. Modern botanical and philological studies have, however, helped greatly in arriving at a correct identification.

In the Bible

The Bible mentions about 100 names of plants, the bulk of them of Ereẓ Israel, the others being trees of Lebanon and tropical plants that yield an aromatic substance or were used in incense. (See Table: Plants in the Bible and Mishnah.) These names refer to specific plants, but some are generic names, such as koẓ ve-dardar ("thorns and thistles") and shamir vashayit ("briars and thorns"). Although the biblical plants are chiefly those which were economically important, they are to a large extent mentioned fortuitously. The carob, for example, although undoubtedly grown at that time, is not mentioned in the Bible, while specific vegetables are mentioned in one verse only of the Bible; and these are the vegetables of Egypt for which the children of Israel longed during their wandering in the wilderness (Num. 11:5).

In Talmudic Literature

The Mishnah, the Talmuds, and the Midrashim add hundreds of names of plants to those mentioned in the Bible. They are particularly numerous in the Mishnah of Zera'im which treats of laws connected with agriculture. In the aggadic Midrashim, too, many plants are mentioned in simile and parable. In all, the ancient literature on Ereẓ Israel mentions close to 500 names of flora. The Babylonian Talmud refers to scores of plants of Babylonia and its neighborhood. In the Table: Plants in Bible and Mishnah, only one identification is given. Alternative suggestions of identification will be found in the individual articles.

bibliography:

H.B. Tristram, Natural History of the Bible (1877⁵); J. Schwarz, Tevu'ot ha-Areẓ (1900); Loew, Flora; G. Dalman, Arbeit und Sitte in Palaestina, 7 vols. in 8 (1928–42); H.N. and A.L. Moldenke, Plants of the Bible (1952); J. Feliks, Ha-Ḥakla'ut be-Ereẓ Yisrael bi-Tekufat ha-Mishnah ve-ha-Talmud (1963); idem, Kilei Zera'im ve-Harkavah (1967); idem, Olam ha-Ẓome'aḥ ha-Mikra'i (1968²), contains additional bibliography. add. bibliography: Feliks, Ha-Ẓome'aḥ.

[Jehuda Feliks]

319. Plants

See also 5. AGRICULTURE ; 54. BOTANY ; 167. FLOWERS ; 188. GRASSES ; 241. LEAVES ; 302. ORGANISMS ; 401. TREES .

acidophobia

an inability to accommodate to acid soils. Cf. basophobia. —acidophobic, adj.

amensalism

a parasitic relationship between plants that has a destructive effect on one and no effect on the other.

apheliotropism

the tendency of some plants to grow in a direction away from the sun.

apogeotropism

the tendency of some plants to grow away from the earth and the pull of gravity. —apogeotropic, adj.

aquapontics

the cultivation of plants in nutrient solutions, usually for commercial purposes. Cf. hydroponics. —aquapontic, adj.

aquiculture

hydroponics. —aquicultural, adj.

auxography

the measurement of the swelling and shrinking of parts of plants. —auxographic, adj.

basophobia, basiphobia

an inability to accommodate to alkaline soils. Cf. acidophobia. —basophobic, basiphobic, adj.

biodynamics

the study of the physiological processes of plants and animals. —biodynamic, biodynamical, adj.

biostatics

the study of the relation between structure and function in plants and animals. —biostatical, adj.

biota

the animal or plant life of a particular region.

botanomancy

a form of divination involving the examination of plants.

caricography

the description of plants belonging to the genus Carex.

caricology

the study of sedges. —caricologist, n.

cecidiology, cecidology

Biology. the study of galls produced on trees and plants by fungi, insects, or mites. —cecidiologist, cecidologist, n.

chlorosis

1. a diseased condition of plants in which green parts lose their color or turn yellowish.

2. the process by which floral parts of a plant turn into leaves. Also chloranthy. See also 122. DISEASE and ILLNESS .

citriculture

the cultivation of citrus fruits, as lemons, oranges, etc. —citriculturist, n.

crescography

a technique for making apparent to the eye the successive stages of plant growth. —crescographic, adj.

cumaphytism

the procedures involved in adapting plants for growth under surf conditions. —cumaphytic, adj.

dendrophilia

the apparent preference of some plants, as orchids, to grow in or near trees. —dendrophilous, adj.

desmidiology

the study of microscopic single-celled algae. —desmidiologist, n.

diatropism

the capacity or tendency of some plants to adopt a position transverse to the line of force of an external stimulus. —diatropic, adj.

dichogamy

the condition, in some flowering plants, in which the pistils and stamens mature at different times, thus preventing self-pollination. —dichogamous, adj.

ecesis

the transplanting of a plant to a new environment.

epiphytism

a form of mutualism in which one plant lives on the surface of another, as moss on a tree. —epiphyte, n.

etiolation

1. the process of growing plants away from the light to make them white and crisp, especially in vegetable gardening.

2. the condition of the plants grown in this manner. See also 122. DISEASE and ILLNESS .

exostosis

a knot growing on the stem or root of a plant. See also 52. BONES .

florimania

a mania for plants and flowers.

fungicide

a substance that kills fungi or retards the growth of spores.

halophytism

the ability of certain plants to grow normally in solis having a high mineral salt content. —halophyte, n. —halophytic, adj.

heliophilia

an attraction or adaptation to sunlight, as the sunflower. —heliophile, n. —heliophilic, heliophilous, adj.

heliotaxis

a tendency of certain plants to move in response to sunlight.

heliotropism

the tendency in some plant species to turn or grow toward sunlight. —heliotrope, n. —heliotropic, adj.

herbalist

a person who collects or deals in herbs, especially for medicinal purposes. See also 54. BOTANY .

herbarist

Obsolete, a herbalist.

herbicide

a substance for destroying plants, especially weeds or other unwanted species; a weed-killer. —herbicidal, adj.

heterosis

abnormal development, especially increased size, in plants or animals, usually as a result of cross-breeding.

hydrophily

ombrophily.

hydrophytism

the ability of certain plants to grow naturally in water or in highly moist soils. —hydrophyte, n. —hydrophytic, adj.

hydroponics

the science of growing plants in specially prepared solutions instead of in soil. Cf. aquapontics. —hydroponic, adj.

hypertrophy

excessive growth of one part of a plant to the disadvantage or detriment of the plant as a whole. See also 51. BODY, HUMAN ; 368. SIZE . —hypertrophic, hypertrophical, hypertrophous, adj.

hyponasty

an increase in growth in a lower part of a plant causing it to bend upward. —hyponastic, adj.

mangonism

Obsolete, any procedure for raising plants under other than natural conditions of growth.

mesophytism

the ability of certain plants to grow naturally in moderate but constant moisture. —mesophyte, n. —mesophytic, adj.

mycolatry

the worship of fungi, especially mushrooms.

olericulture

the branch of horticulture that specializes in the cultivation of edible plants. —olericultural, adj.

ombrophily

the capacity of some plants to thrive in the midst of copious rain. Also called hydrophily . —ombrophilic, ombrophilous, adj.

parasitism

a relationship between plants in which one gains sustenance from the other. See also 16. ANIMALS ; 44. BIOLOGY .

perigyny

the state of having the pistils, stamens, petals, etc., arranged around a cuplike receptacle. —perigynous, adj.

pesticide

any chemical substance used for killing pests, as insects, weeds, etc.

philobotanist

Rare. a lover of plants.

photodynamics

the science or study of light in relation to the movement of plants. —photodynamic, photodynamical, adj.

photonasty

the tendency in certain plant species to respond to light by developing sufficient cellular force or growth on one side of an axis to change the form or position of the axis, as in the opening and closing of the flowers of four-o’clocks. Cf. thermonasty. —photonastic . adj.

photoperiodism

the study of the relative amounts of light and darkness in a 24-hour period required to best effect the growth, reproduction, and flowering of plant species or the growth and reproduction of animals. Also photoperiodicity . Cf. thermoperiodism . —photoperiodic, photoperiodical, adj.

photophilia, photophily

the necessity, in some plant species, for exposure to strong light. —photophile, photophilic, photophilous, adj.

photosynthesis

the synthesis of complex organic substances from carbon dioxide, water, and inorganic salts, with sunlight as the energy source and a catalyst such as chlorophyll. —photosynthetic, adj.

phototropism

motion in response to light, either toward it or away from it, as manifested by certain plants. —phototropic, adj.

phytogenesis, phytogeny

the origin and evolution of plants. —phytogenetic, phytogenetical, phytogenic, adj.

phytoserology

the identification, classification, and study of plant viruses. —phytoserologist, n. —phytoserologic, phytoserological, adj.

plagiotropism

the tendency of some plants to diverge from the vertical in their growth. —plagiotropic, adj.

rheotropism

the tendency of some plants to respond to a current of water by growing with it (positive rheotaxis) or against it (negative rheotaxis).

saprophytism

the ability of certain plants to live in dead or decaying organic matter. —saprophyte, n. —saprophytic, n., adj.

sclerosis

the hardening of the cell wall of a plant, as by the formation of wood. See also 51. BODY, HUMAN . —sclerotic, adj.

stirpiculture

selective breeding to develop strains with particular characteristics. —stirpicultural, adj.

sycomancy

the art of divination by inspection of figs or flg leaves.

thermonasty

the tendency in certain plant species to respond to temperature changes by developing a sufficient cellular force or growth on one side of an axis to change the form or position of the axis, as in the closing or folding of rhododendron leaves in cold air. Cf. photonasty. —thermonastic, adj.

thermoperiodism

the study of the relative day and night temperatures required, in a 24-hour period, to achieve the best growth, reproduction, or flowering of plant species or the growth and reproduction of animals. Also thermoperiodicity. Cf. photoperiodism . —thermoperiodic, thermoperiodical, adj.

thermotropism

the tendency in some plant species to turn toward or away from a source of heat. —thermotropic, thermotropical, adj.

xenogamy

cross-fertilization in plants or flowers.

xerophilia, xerophily

the ability of some plants to survive in dosert or salt marsh areas by storing fresh water internally. —xerophilic, xerophilous, adj.

xerophytism

the natural adaptation of plants living under desert or marsh conditions to store water internally. —xerophyte, n. —xerophytic, adj.