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Legumes

Legumes As Weeds

Some species of legumes that are cultivated in agriculture or horticulture have become naturalized in semi-natural and natural habitats, and some of these are locally considered to be invasive weeds. Examples of these species include Scotch broom, gorse, garden lupines, vetches, and some other species. These are rarely considered important enough as weeds to be the specific targets of control programs.

One exception, however, is the kudzu vine (Pueraria lobata), native to Japan and introduced to the southeastern United States as a forage plant and for use in controlling erosion. This species is considered to be a serious, invasive weed in some places. Control methods for the kudzu include the use of herbicides and the excavation of its large, underground, roots.

A few species of legumes have foliage or seeds that can be extremely toxic to humans and domestic animals, and these may be actively controlled to reduce the risks of poisoning. The best North American examples of toxic legumes that are sometimes considered to be pests because they can poison livestock on rangelands are the locoweeds (Oxytropis spp., and to a lesser degree, Astragalus spp.). The precatory pea or rosary bean (Abrus precatorius) grows wild in subtropical and tropical climates and was introduced as an ornamental plant to south Florida where it is now naturalized. This species has small (less than 0.4 in [1 cm] long), very attractive, crimson-red seeds, with one jet-black spot at one end, but these are so toxic that a single one can kill a person if chewed. Precatory peas are sometimes used to make beautiful seed-necklaces, but these can be deadly in the hands of children.

Resources

Books

Duke, J. A. Handbook of Legumes of World Economic Importance. New York: Plenum Press, 1981.

Hvass, E. Plants That Serve and Feed Us. New York: Hippocrene Books, 1975.

Judd, Walter S., Christopher Campbell, Elizabeth A. Kellogg, Michael J. Donoghue, and Peter Stevens. Plant Systematics: A Phylogenetic Approach. 2nd ed. with CD-ROM. Suderland, MD: Sinauer, 2002.

Klein, R.M. The Green World: An Introduction to Plants and People. New York: Harper and Row, 1987.


Bill Freedman

KEY TERMS


Bilateral symmetry

—In reference to flower shape, this indicates that a vertical sectioning of the flower will produce two halves with symmetric features.

Compound leaf

—A leaf in which the blade is separated into several or many smaller units, called leaflets, arranged along a central petiole or stalk known as a rachis.

Cultivar

—A distinct variety of a plant that has been bred for particular, agricultural or culinary attributes. Cultivars are not sufficiently distinct in the genetic sense to be considered to be subspecies.

Legume

—This is a type of fruit, also known as a pod, which is developed from a single ovary but contains multiple seeds and opens along a single seam when ripe.

Nitrogen fixation

—The conversion of atmospheric nitrogen gas (N2) to ammonia or an oxide of nitrogen. This process can occur biologically through action of the microbial enzyme, nitrogenase, or inorganically at high temperature and pressure.

Nitrogenase

—An enzyme synthesized by Rhizobium and some other microorganisms that is capable of cleaving the triple bond of nitrogen gas (N2), generating ammonia (NH3), a type of fixed nitrogen that plants can utilize in their nutrition.

Rhizome

—This is a modified stem that grows horizontally in the soil and from which roots and upward-growing shoots develop at the stem nodes.

Tendril

—A spirally winding, clinging organ that is used by climbing plants to attach to their supporting substrate. In the legume family, tendrils are derived from modified leaflets.

Weed

—Any plant that is growing abundantly in a place where humans do not want it to be.

Additional topics

Science EncyclopediaScience & Philosophy: Laser - Background And History to Linear equationLegumes - Biology Of Legumes, Native Legumes Of North America, Legumes In Agriculture, Other Economic Products Obtained From Legumes