Plant Ecology

Glossary of Key Terms

Glossary of Key Terms

Term	Definition
Abscisic acid	A plant growth inhibitor that plays a regulatory role in seed and bud dormancy. Chilling treatments can reduce its concentration, helping to break dormancy.
Cardinal Temperatures	The minimum, optimum, and maximum temperatures required for a specific physiological function in a plant. These temperatures can differ for various functions within the same plant and can be influenced by developmental stage and other environmental factors.
Cold Hardening	The process by which plants improve their ability to withstand low temperatures. It is associated with cellular chemical changes such as an increase in bound water, a decrease in total water, a change of starch to sugars, and an increase in pentosans.
Ecology	The study of the relationship between organisms and the environment and the interrelationships between organisms.
Environmental physiology	An alternative name for physiological ecology, emphasizing the study of the effects of environmental factors on processes within organisms.
Gibberellic acid	A plant growth stimulator that can break dormancy in seeds and buds, often by reversing the effects of inhibitors like abscisic acid.
Juglone	A toxic compound (5-hydroxynaphthaquinone) extracted from the mature hulls and roots of the black walnut tree (Juglans nigra) that is inhibitory to plants like tomato and alfalfa.
Phenolics	A class of chemical inhibitors produced by plants, including compounds like chlorogenic acid, ferulic acid, gallic acid, and various tannins. They are known to inhibit enzyme systems, affect hormone activity, and reduce nodulation in legumes.
Photoperiodism	The response of organisms to the relative lengths of light and dark periods, which regulates phenomena such as flowering, bulb formation, dormancy, and seed germination.
Photosystem I	A component of the photosynthetic light reactions with an absorption peak in the far-red light spectrum (700 mμ).
Photosystem II	A component of the photosynthetic light reactions with an absorption peak around 672 mμ. Its action can be impaired in plants grown in light intensities to which they are not adapted.
Physiological ecology	The study of the effects of environmental factors on processes in organisms, or the study of the physiological basis of ecological behavior.
Phytochrome	A pigment involved in photoperiodic timing that exists in two convertible forms: P_r (absorbs red light at 660 mμ) and P_fr (absorbs far-red light at 730 mμ). The P_fr form is considered inhibitory to flowering in some plants.
Terpenes	Volatile organic compounds, such as camphor and cineole produced by shrubs like Salvia, that can inhibit the growth of other plants by reducing mitochondrial respiration and decreasing cell membrane permeability.
Transcinnamic acid	An inhibitor produced by the guayule plant (Parthenium argentatum) that was found to suppress the growth of guayule seedlings.
Transpirational cooling	The process by which water evaporation from leaves (transpiration) helps to lower leaf temperatures, preventing them from rising to detrimental levels.
Turgor pressure	The internal pressure of a plant cell against its cell wall, which is critical for cell enlargement and the opening/closing of stomates. A reduction in turgor pressure due to water deficit can slow or stop plant growth.