earthworm castsSee castings, earthworm.

Eckhardt method A rapid screening method in electrophoretic analysis of plasmid DNA from recombinant colonies. The colonies may be lysed and the DNA applied directly to an agarose gel, or the colonies may be lysed in the well of the gel. Plasmids containing insert DNA are larger than the normal plasmid vector molecules, which are easily distinguished by differences in electrophoretic mobility.

ecocline Series of biotypes within a species that shows a genetic gradient correlated with a gradual environmental gradient.

ecological niche Role of an organism in an ecological system.

ecological race Group of local populations within a species in which individuals have similar environmental tolerances. Wide-ranging species may consist of many ecological races.

ecology The study of communities of living things and the relationships between organisms and their environment.

ecotone Transition zone between two vegetational types or vegetational regions.

EDTA Part II.

efficiency Degree to which a plant or vegetation converts radiant energy into organic compounds; efficiency may depend on degree of utilization of necessary environmental components.

electroblotting The electrophoretic transfer of macromolecules (DNA, RNA or protein) from a gel in which they have been separated onto a support matrix such as a nitrocellulose sheet. This procedure is an alternative to the capillary transfer used in techniques such as Southern and northern blotting.

electrophoresis A technique for separating different types of molecules based on their patterns of movement in an electrical field. See also polyacrylamide gel electrophoresis; sequencing gel.

ELISA Enzyme-linked immunosorbent assay: An immunological technique employing two antibodies. The primary antibody is specific for the antigen of interest, and the second is an antiglobin antibody to which an enzyme, such as horseradish peroxidase, has been attached. The primary antibody is first bound to the antigen and then the antiglobin antibody is bound to the primary antibody. Assays for the enzyme activity thus indicate the location and amount of primary antibody present and, indirectly, that of the antigen.

embryo percent (1) The amount of embryo compared with endosperm and other seed parts. (2) The percent of embryo in the whole seed.

embryogenesis The process of initiation and development of embryos from zygotes or, in somatic embryogenesis, of complete bipolar plant structures from somatic cells that parallel the developmental pathway of zygotic embryos. In the latter case, such embryos may be either adventitious or de novo in origin. Synonym: embryogeny.

embryoid (1) Mass of cells or tissue that resembles an embryo; i.e., an embryolike structure. (2) Somatic embryo.

enclosure (1) An area enclosed by fence or wall to confine animals. (2) A caged or fenced area within a pasture to exclude grazing.

endarch Primary xylem in which the development is from the center towards the outside. Typical of stems. Compare exarch.

endogen A plant in whose primary stem the vascular bundles are not arranged in concentric circles and whose older stems do not have distinct wood and bark layers.

endonuclease An enzyme that cleaves within the polynucleotide chain. See also nuclease; restriction endonuclease.

endophyte absence Absence of the endophytic fungus Acremonium coenophialum in the fescue tissue, plant, or population being discussed.

endophyte-free seed Tall fescue seed free of the Acremonium coenophialum endophyte.

enhancer element A DNA sequence found in eukaryotes and certain eukaryotic viruses that acts in cis in either orientation to increase the use of a promoter and transcription from a gene when located up to several kilobases from the gene it affects. Synonym: enhancer sequence

ensilageSee silage.

enzymatic degradation Chemical breakdown of a given substance by the specific enzyme catalyst for that particular chemical reaction of a biological process.

enzyme-linked immunosorbent assaySee ELISA.

epigeal germination A type of germination in which the cotyledons are raised above the ground by elongation of the hypocotyl.

episome A plasmid that can integrate into the bacterial chromosome.

ergopeptine; ergopeptide A class of alkaloids produced by clavicepitaceous fungal organisms, including ergovaline, ergotamine, and related ergotlike alkaloids.

escape A plant introduction that has accidentally escaped from cultivation.

ether extract Fats, waxes, oils, and similar plant components that are extracted with warm ether in chemical analysis.

etiolated Characterized (as a result of growth in the absence of light) by the development of a number of symptoms such as yellowing, elongation, thin stems, and failure of leaf expansion.

eukaryote Part II.

euploid (1) Characterizing a cell in which the nucleus contains exact multiples of the haploid number of chromosomes. (2) Such a cell or organism. See also -ploid.

exarch Primary xylem in which the development is from the outside, toward the center. Typical of roots. Compare endarch.

exonuclease An enzyme that cleaves nucleotides one at a time from either the 3' or 5' end of a polynucleotide chain. See also nuclease.

explant culture The maintenance or growth of an explant in culture.

explant tissue The excised tissue of a plant (or seed) used to establish a cell or tissue culture system.

extrachromosomal Located elsewhere than the nuclear chromosome, such as in an organelle or on a plasmid.

extrusion cooking A process where a mash or granular mixture of starch and/or proteins of cereals or oilseeds is preconditioned by exposure to steam and then cooked in a continuous extruder. The extruder consists of a series of spirals that force the cereal mash into an increasingly restricted area, whereby the temperature and pressure are increased rapidly, reaching 300 to 400 psi (~2-2.8 MPa) and 300 to 500 °F (~150-260 °C) for a short period of time (15-20 s). The pressure is released and the hot, plasticized material expands as it passes through a series of dyes. The extruded material is then dried. The process is used in production of textured vegetable proteins, pet foods, instant foods, and many other products.