Chapter 39

Environmental Complexity

The various physical and chemical factors in an organism's environment that affect its physiological processes.

Tropism

Growth response of a plant toward or away from a stimulus.

Phototropism

A plant's growth response to light, typically resulting in leaves orienting towards the light source.

Thigmotropism

A growth response of plants to touch, often shown by tendrils wrapping around objects for support.

Nastic Response

A non-directional movement response in plants, such as opening and closing flowers in response to light.

Morphogenic Response

A response that results in a change in the form or structure of a plant tissue or organ.

Auxin

A plant hormone that regulates growth, particularly in shoot elongation and apical dominance.

Vernalization

The process by which cold temperatures induce flowering or transitions in plant reproductive cycles.

Ethylene

A plant hormone involved in fruit ripening and the abscission of leaves.

Photoperiodism

A plant's physiological reaction to the length of day or night, which influences flowering.

Statocytes

Specialized plant cells that perceive gravity.

Threshold

The minimum level of stimulus required to produce a response in perception and transduction.

Chemotaxis

A movement response towards or away from a chemical stimulus.

Brassinosteroids

Hormones that play a role in plant growth and development, such as leaf morphogenesis and vascular differentiation.

Gibberellin

A plant hormone that promotes stem elongation, seed germination, and flowering.

Phase Change

The transition of a plant from juvenile to adult phase, impacting its ability to flower.

Endogenous Rhythms

Internal biological cycles in plants that regulate metabolic processes, typically aligned with the day-night cycle.

Cytokinins

Plant hormones that promote cell division and shoot development, often interacting with auxin.

Abscisic Acid

A plant hormone that helps the plant respond to stress, such as drought, by affecting stomatal closure and leaf abscission.

Photomorphogenesis

The process by which light affects plant growth and development.

Apical Dominance

The phenomenon where the main central stem of the plant is dominant over other side stems, influenced by auxin levels.

Chemotropism

The growth response of a plant to a chemical gradient.

Photoperiodic Induction

The process by which plants detect and respond to the duration of light and dark periods to trigger flowering.