Plant Responses to Internal and External Signals

Flashcards relating to Plant Responses to Internal and External Signals

Etiolation

Morphological adaptations for growing in darkness

De-etiolation

Changes in which shoots and roots grow normally after exposure to light

cGMP and Ca2+

Activate protein kinase directly

Protein phosphatases

Switch off the signal transduction

Plant hormones

Chemical signals that modify or control one or more specific physiological processes within a plant

Auxin (IAA)

Stimulates stem elongation (low concentration only); promotes the formation of lateral and adventitious roots; regulates development of fruit; enhances apical dominance; functions in phototropism and gravitropism; promotes vascular differentiation; retards leaf abscission

Cytokinins

Regulate cell division in shoots and roots; modify apical dominance and promote lateral bud growth; promote movement of nutrients into sink tissues; stimulate seed germination; delay leaf senescence

Gibberellins (GA)

Stimulate stem elongation, pollen development, pollen tube growth, fruit growth, and seed development and germination; regulate sex determination and the transition from juvenile to adult phases

Abscisic acid (ABA)

Inhibits growth; promotes stomatal closure during drought stress; promotes seed dormancy and inhibits early germination; promotes leaf senescence; promotes desiccation tolerance

Ethylene

Promotes ripening of many types of fruit, leaf abscission, and the triple response in seedlings (inhibition of stem elongation, promotion of lateral expansion, and horizontal growth); enhances the rate of senescence; promotes root and root hair formation; promotes flowering in the pineapple family

Brassinosteroids

Promote cell expansion and cell division in shoots; promote root growth at low concentrations; inhibit root growth at high concentrations; promote xylem differentiation and inhibit phloem differentiation; promote seed germination and pollen tube elongation

Jasmonates

Regulate a wide variety of functions, including fruit ripening, floral development, pollen production, tendril coiling, root growth, seed germination, and nectar secretion; also produced in response to herbivory and pathogen invasion

Strigolactones

Promote seed germination, control of apical dominance, and the attraction of mycorrhizal fungi to the root

Tropism

Any response resulting in curvature of organs toward or away from a stimulus

Auxin

Any chemical that promotes elongation of coleoptiles

Apical dominance

A terminal bud’s ability to suppress development of axillary buds

Gibberellins

Stimulate growth of leaves and stems

Abscisic acid (ABA)

Slows growth

Seed dormancy

Ensures that the seed will germinate only in optimal conditions

Triple response

Slowing of stem elongation, a thickening of the stem, and a curvature to cause the stem to start growing horizontally

Senescence

The programmed death of cells or organs or the entire plant

Brassinosteroids

Are chemically similar to the sex hormones of animals; they induce cell elongation and division in stem segments; they slow leaf abscission and promote xylem differentiation

Strigolactones

Stimulate seed germination; suppress adventitious root formation; help establish mycorrhizal associations; help control apical dominance

Photomorphogenesis

Effects of light on plant morphology

Action spectrum

Depicts the relative response of a process to different wavelengths

Two major classes of light receptors

Blue-light photoreceptors and phytochromes

Phytochromes

The photoreceptors responsible for the opposing effects of red and far-red light

Circadian rhythms

Cycles that are about 24 hours long and are governed by an internal “clock”

Photoperiod

The relative lengths of night and day, is the environmental stimulus plants use most often to detect the time of year

Photoperiodism

A physiological response to photoperiod

Short-day plants

Plants that flower when a light period is shorter than a critical length

Long-day plants

Plants that flower when a light period is longer than a certain number of hours

Day-neutral plants

Flowering is controlled by plant maturity, not photoperiod

Florigen

A protein governed by the CONSTANS gene

Gravitropism

Roots show positive gravitropism; shoots show negative gravitropism

Thigmomorphogenesis

Changes in form that result from mechanical disturbance

Environmental stresses

Have a potentially adverse effect on survival, growth, and reproduction

Heat-shock proteins

Help protect other proteins from heat stress

The first line of immune defense

Depends on the plant’s ability to recognize pathogen-associated molecular patterns (PAMPs)

A second level of plant immune defense

Effector-triggered Immunity

The hypersensitive response

Causes cell and tissue death near the infection site; induces production of enzymes that attack the pathogen; stimulates changes in the cell wall that confine the pathogen

Animals eating plants, is a stress that plants face in any ecosystem

Herbivory