Plant Control Systems and Defenses

Vocabulary

abscisic acid (ABA)

a plant growth hormone that controls dormancy and leaf aging

abscission

the natural separation of flowers, fruit, or leaves from the parent plant

apical dominance

the suppression of lateral bud development on growing shoots

auxin

a plant growth hormone that controls root growth, bud formation, and fruit maturity

axillary bud

a structure at the axil (angle between a leaf and the branch it attaches to) of a branch that may develop into a new branch

circadian rhythm

repeated process that occurs within a 24-hour period; these patterns continue even without external cues

cytokinin

a class of plant hormones that influences tissue growth

ethylene

a plant hormone that controls the ripening of fruit

geotropism

the effect of gravity on plant movement

gibberellin

one of a class of plant hormones that regulates stem length, seed germination, flowering, sexual expression, and leaf and fruit ripening

idioblast

specialized cell, found in stems and leaves, that makes eating a plant unpleasant, such as sharp crystals within cells

jasmonate

a specific hormone within leaves and stems that triggers a reaction when a plant's surface is wounded

nastic movement

quick movement by plants in reaction to temperature, humidity, or touch; these movements are reversible and repeatable

nutation movement

bending movement by plants in which the plant inclines in a particular direction

pathogen

disease-causing organism or virus that causes harm to a host organism

phototropism

plant movement based on light

phytohormone

chemical substance in plants that signals growth and development

plant growth regulator (PGR)

chemical compound that signals growth and development in plants

senescence

the aging and decay of plant matter

structural defense

protective plant part, such as a spine or thorn

tactic movement

a plant's response to touch

trichome

hairlike outgrowth on a plant shoot that functions to deter herbivores

triple response

the reaction of a plant shoot to avoid an obstacle to growth

tropism

a positive or negative response of a plant to a stimulus

turgor movement

a reversible positioning caused by changes in water content in a plant

volatile organic compound (VOC)

organic compound that easily vaporizes; used for communication in plants