Plant Hormones – Vocabulary Flashcards

A vocabulary set covering key hormone concepts, tropisms, plant defenses, and related topics from the Plant Hormones notes.

Plant hormones

Chemical messengers produced by plants that regulate growth, development, and responses to the environment.

Auxins

A class of plant hormones that promote cell elongation, apical dominance, root initiation, and tropic responses; example: indole-3-acetic acid (IAA).

IAA (Indole-3-acetic acid)

The most common natural auxin; stimulates cell elongation, root formation, and tropic responses.

Gibberellins

Group of plant hormones that promote stem elongation, seed germination, and flowering; includes GA3 among forms.

GA3 (Gibberellic acid 3)

A gibberellin used to promote growth, cell elongation, and germination; affects fruit development in some crops.

Abscisic acid (ABA)

Plant hormone that inhibits growth, promotes dormancy, closes stomata under water stress, and can influence germination and seed dormancy.

Phototropism

Growth response toward light, caused by redistribution of auxin to the shaded side.

Geotropism

Growth in response to gravity; roots typically exhibit positive geotropism (downward), shoots negative geotropism (upward).

Hydrotropism

Growth toward moisture or water.

Thigmotropism

Growth response to touch or physical contact.

Chemotropism

Growth toward or away from chemicals or chemical stimuli.

Tropism

Directional growth or movement of a plant part in response to a stimulus.

Adventitious roots

Roots that form from non-root tissues (e.g., stems); often induced by auxins in cuttings.

Apical dominance

Growth of the main shoot apex suppresses lateral bud growth; removal promotes branching.

Stomatal closure

Closing of stomata, often triggered by ABA, to reduce water loss during drought.

Seed dormancy

A period when seeds do not germinate despite favorable conditions; ABA contributes to this state.

Bud dormancy (apical and lateral)

Winter dormancy of buds modulated by ABA and environmental cues.

Tissue culture auxins

Use of auxins in growth medium (e.g., agar) to induce rooting in plant tissue culture.

Auxins as herbicides

Certain auxins cause uncontrolled growth in broad-leaved weeds, leading to death; used as herbicides.

Xerophytes

Desert-adapted plants with features like reduced leaves or thorns to minimize water loss.

Mechanical defence

Physical defenses of plants (e.g., thorns, thick bark, waxy cuticle) that deter herbivores.

Thorns

Sharp protective structures on plants, often modified from leaves or stems.

Bark

Hard protective outer layer of stems that helps deter predators and damage.

Waxy cuticle

Waxy protective layer on leaves that reduces water loss and pathogen entry.

Secondary metabolites

Chemicals produced by plants for defense rather than growth, including alkaloids, tannins, and terpenoids.

Alkaloids

Nitrogen-containing compounds that are often poisonous and serve as chemical defenses.

Tannins

Phenolic compounds with antiseptic properties that deter herbivory by affecting digestion.

Terpenoids

Large class of secondary metabolites with defensive roles and diverse functions (e.g., essential oils).

Clinostat

A device that rotates to negate gravity effects in tropism experiments.

Germination triggers by gibberellins

Gibberellins released from the embryo stimulate seed germination by promoting enzymatic activity.

Positive geotropism

Growth direction toward gravity (e.g., roots growing downward).

Negative geotropism

Growth direction away from gravity (e.g., shoots growing upward).