Glossary of Crop Science Terms - Browse

landscape A collective term for all the natural features (such as fields, hills, forests, water, etc.) that distinguish one part of the earth's surface from another part. Usually used in reference to that land or territory which the eye can comprehend in a single view, including all its natural characteristics.

lateral shoot Shoots originating from vegetative buds in the axils of leaves or from the nodes of stems, rhizomes, or stolons.

lawngrass See turfgrass.

layering, soil Stratification within a soil profile, which may affect conductivity and retention of water, soil aeration, and rooting; can be due to construction design, topdressing with different textured amendments, inadequate on-site mixing of soil amendments, or blowing and washing of sand or soil.

Leader-follower grazing Usage: Not a recommended term. See first-last grazing.

leaf, early A developmental stage; requires a reference point to be useful.

lesion A wound or injury; more specifically, a circumscribed pathological alteration of tissue.

library See gene bank.

ligation reaction The process of joining two linear nucleic acid molecules together via a phosphodiester bond. In a cloning experiment, a restriction fragment is often ligated to a linearized vector molecule.

light intensity The output of light per unit area or per unit solid angle at a source. Usage: Not to be used to describe the amount of irradiation at any plane away from the source. To describe a flux of radiant energy at a plane away from a source, light flux (density) or radiant flux (density) (in amount per unit area per unit time) are appropriate. The appropriate terms for the receipt of radiation on a surface are irradiance (in energy or quantum units) and illuminance (in photometric units). Light may be defined variously as radiation in the visible portion of the spectrum with wavelengths 400 to 700 nm up to 380 to 780 nm.

lignify To make woody.

limiting factor An environmental variable (or, less often, a plant trait) found at a level that restricts the performance of the organism.

line variety One or more lines of self- or cross-fertilizing plants and single-line facultative apomicts, having largely the same genetic background, that are similar in essential and distinctive characteristics and are maintained or reproduced by controlled self- or sib-fertilization or line crossing of the plants (for self- or cross-fertilizing plants) or close generation control (for single-line facultative apomicts). Usage: The sameness of genetic background is defined as a theoretical coefficient of parentage > 0.87 and 95% apomixis for the single-line facultative apomicts, except that where it is not possible to achieve 95% apomixis, single-line facultative apomicts with a level of apomixis as low as 80% may be classed as line varieties, even though the variant plants present may differ in morphological characteristics.

linkage The tendency for certain genes to be inherited together, due to their physical proximity on the chromosome.

lint index Weight in grams of fiber from 100 seed.

lint quality An estimate of the fitness for use of cotton fiber, based on measurement of various properties of a sample.

liquid chromatography An analytical method based on the separation of the components of a mixture in solution by selective absorption. All systems contain a moving solvent, a means of producing solvent motion (gravity or a pump), a means of sample introduction, a fractioning column, and a detector. Innovations in functional systems provide the analytical capability for operating in three separation modes: (i) liquid-solid partition, in which separations depend on relative solubilities of sample components in two immiscible solvents (one of which is usually water); (ii) liquid-solid absorption, where the differences in polarities of sample components and their relative absorption on an active surface determine the degree of separation; and (iii) molecular size separations, which depend on the effective molecular size of sample components in solution. Common solvents include isooctane, methyl ethyl ketone, acetone-chloroform, tetrahydrofuran, hexane, and toluene. Common packing materials include silica gel, alumina, glass beads, polystyrene gel, and ion exchange resins.

local population Group of individuals of the same species growing near enough to each other to interbreed and exchange genes.

locus Any site that has been defined genetically. A locus may be a gene, part of a gene, or a DNA sequence that has some regulatory role, and may be occupied by different sequence forms (alleles). Plural: loci.

lodging, stalk Stalk breakage above ground level.

low-copy-number plasmid See stringent plasmid.

low-temperature discoloration The loss of chlorophyll and associated green color that occurs in turfgrasses under low-temperature stress.