Tannin
A secondary carbon compound produced in the leaves of some plants, which can act to deter against herbivory. This defensive compound usually requires more carbon than nitrogen in its synthesis.
Taxon
A large group of closely related organisms that possess a high degree of similarity with respect to anatomy, physiology and biochemistry.
Taxonomy
The science or technique of classifying plants and animals according to species, genus, etc.
Temperature departure
The difference obtained when a temperature is subtracted from the mean temperature of a significantly longer time period.
Thermohaline circulation
The system of surface and subsurface ocean currents that is driven by temperature and salinity differences that create density gradients between adjoining water masses. They are responsible for moving great amounts of thermal energy around the globe.
Thylakoid membranes
Membranes within chloroplasts that contain chlorophyll (and other pigments that absorb sunlight) and specialized protein complexes that convert sunlight into usable cellular energy (ATP) during photosynthesis.
Topography
Having to do with elevation or "lay of the land," i.e., surface features.
Transcript
A mobile copy of information encoded for by a gene, also known as mRNA. Its genetic information is directly used to synthesize proteins.
Transcription
The process wherein the genetic code comprising a gene on double-stranded DNA is converted into conserved genetic code on single-stranded mRNA.
Transform
To genetically alter a plant or organism.
Transformant
A plant or organism that has been genetically altered.
Transpiration
The process by which water vapor is lost from plants, evaporating from cell walls just below the surface of the leaf and diffusing into the air through small stomatal pores.
Tree basal area
The cross-sectional area of living tree trunks per unit ground area.
Tritium
An isotope of hydrogen having an atomic weight of three: 3H.
Tropical cyclone
Any storm that originates in or near the tropics, including tropical depressions, tropical storms, and hurricanes (a.k.a. typhoons or cyclones).
Tropical storm
A storm of tropical origin that has maximum sustained wind speeds between 35 and 64 knots (40 to 74 mph).
Tropopause
The atmospheric layer separating the stratosphere from the troposphere. It marks the transition from temperatures that decrease with increasing height within the troposphere, to an atmospheric region that experiences increasing temperatures with height.
Troposphere
The lowest layer of the atmosphere, extending from the surface to an altitude of 10 to 15 kilometers. The troposphere is the most dense and unstable layer of the atmosphere.
Turgor pressure
The internal pressure exerted on a cell wall by water and solutes pushing against it. This pressure keeps cells turgid and allows non-woody plants and plant parts to remain upright. When turgor pressure is lost, cells become flaccid, causing plants to wilt.