zoning

In general, the demarcation of a planning area by ordinance into zones and the establishment of regulations to govern the use of the land (commercial, industrial, residential, type of residential, etc.) and the location, bulk, height, shape, use, and coverage of structures within each zone

zoonoses

Diseases of non-human animals that may be transmitted to humans or may be transmitted from humans to non-human animals

zooplankton

Free-floating, minute, often microscopic, animals of aquatic systems. They include protozoa, rotifers, crustaceans, and larvae of larger animals, such as annelids and fish, that feed on other plankton.

zygospores

A thick-walled resting cell or spore formed by the fusion of gametangia (or specialized haploid hyphae) of different mating types during the sexual reproduction, as seen in some species of fungi, algae, protists etc

technical crops

Those crops that are not specifically grown for foodstuffs (such as fruit crops, vegetable crops and grain crops), but are specifically grown to yield a useful product for man or industrial processes, such as fiber, oils, rubber, chemicals, resions, energy, waxes, or dyes

tension wood

Abnormal wood found in leaning trees of some hardwood species and characterized by the presence of gelatinous fibers and excessive longitudinal shrinkage. Tension wood may cause warping

terraces

Natural or manmade landforms which run perpendicular to the slope and are bordered on one side by a steep ascending slope and on the other side by a steep descending slope.

terracing

In agronomic practice, the construction of ridges of earth built across a slope with a flat or graded channel to stop soil erosion and control the runoff of water.

testcrosses

A cross between an organism exhibiting the dominant phenotype for a certain trait, but whose genotype for that trait is unknown and an organism that is homozygous recessive for the trait so that the unknown genotype can be determined from that of the offspring.

tetraploidy

A cell, tissue, or organism having four sets of chromosomes.

The Nature Conservancy

An international conservation organization that purchases lands in order to preserve plants, animals and natural communities.

thigmonastic movement

The movement of plant parts in response to non-directional stimuli. The stimulus may be external, such as the movement of Mimosa leaves when touch (thigmonasty), or internal, such as the sudden movement of plant parts due to changes in turgor pressure (seismonasty). Nyctinasty is the movement of organs, such as the opening of flowers during the day and closing at night, in response to the diurnal cycle.

thinning (in forests)

The silvicultural practice of removing excess, diseased or poor quality trees and underbrush to improve the growth, health and value of the standing timber crop.

thinning (plants)

The practice of reducing the number of plants in an area or the quantity of vegetative or reproductive structures on individual plants.

threatened species

Any species which is likely to become an endangered species within the foreseeable future throughout all or a significant portion of its range and which has been designated in the Federal Register by the Secretary of Interior as a threatened species. (Endangered Species Act of 1973) This includes species categorized as rare, very rare, or depleted.

tissue-cultured meat

Meat produced from the skeletal muscle or muscle cells or stem cells in laboratory conditions by using tissue engineering techniques.

tissue banks

Centers for acquiring, characterizing, and storing organs or tissue for future use.

tissue culture

A method of maintaining or growing tissues, organ primordia, whole or parts of organs, in a manner to preserve their structure and/or function.

top dressings

The application of compost or fertilizer on top of the soil during plant growth.

topping (pruning)

The practice of removing the top branches of a tree or shrub.