Plant Hormones and Growth Responses

Flashcards covering key concepts about plant hormones and their roles in growth and development.

Auxin efflux carrier

The PIN protein (e.g., PIN1), which transports auxin out of cells.

Auxin influx carrier

The AUX1/LAX protein, which brings auxin into cells.

Auxin's role in strawberry maturation

Auxin is produced by developing seeds and stimulates fruit growth and maturation.

Vernilization

Exposure of plants to prolonged cold to trigger flowering, typically taking 4 to 12 weeks.

Florigen

A mobile flowering signal (mainly the FT protein) made in leaves and transported to the shoot apical meristem to induce flowering.

Hormones

Chemical messengers that regulate plant growth and development by signaling between cells and tissues, usually in low concentrations.

Classic plant hormones

Auxin, Cytokinin, Gibberellin (GA), Abscisic acid (ABA), Ethylene.

Newcomer hormones

Brassinosteroids, Jasmonic acid, Salicylic acid, Strigolactones.

Coleoptile tip function

The part of the coleoptile that senses the source of light.

Auxin receptor

TIR1.

Cytokinin receptor

CRE1/AHK.

Gibberellin (GA) receptor

GID1.

ABA receptor

PYR/PYL/RCAR.

Ethylene receptor

ETR1 (and related receptors).

Auxin functions in Arabidopsis

Regulates embryogenesis, root and shoot growth, vascular differentiation, apical dominance, and tropisms.

Apical dominance

A phenomenon where the main shoot suppresses the growth of lateral buds.

Cytokinin synthesis

Mostly in the roots.

Effects of IPT overexpression

Leads to high cytokinin levels, delayed leaf senescence, and altered growth patterns.

Triple responses in ethylene treatment

Inhibited stem elongation, thickened stem, horizontal (or radial) growth.

Functions of ethylene

Regulates fruit ripening, leaf abscission, senescence, and responses to stress.

Functions of ABA

Induces seed dormancy, stomatal closure, and helps plants respond to stress.

Causes of dwarf plants

Gibberellin (GA) deficiency or excess DELLA proteins, which repress growth.

DELLA protein function

Represses GA responses, degradation allows growth to occur in the presence of GA.

Briggs’ phototropism experiment outcome

Demonstrated that the phototropic signal originates in the tip and is transmitted to the lower part of the plant for bending.

Most effective light for phototropic response

Blue light.

Statocytes localization

Located in the root cap, especially in the columella cells.

Auxin's effect on horizontally oriented roots

Auxin accumulates on the lower side, inhibiting growth and causing the root to bend downward.

Auxin in root gravitropism

Redistributes to the lower side of the root, inhibiting elongation and causing bending in the direction of gravity.

TC75 mutant gravitropism response

Showed defective gravity sensing, likely due to issues in auxin transport or signaling.

Thigmotropism

A growth response to touch or mechanical stimulation.

Pr and Pfr activity changes

Pr converts to Pfr (active form) in red light; Pfr reverts to Pr in far-red light or darkness.

Long-day plant flowering conditions

Flowers when days are longer than nights, typically in spring or early summer.

Effect of one minute of light on long-day plants

Interrupts the dark period, allowing flowering to occur.

Photoperiod perception organ

Leaves.

Where is florigen produced?

In the leaves.

Role of FT, CO, and GI in flowering

GI stabilizes CO, which activates FT. FT moves to the shoot meristem to induce flowering.

FLC during vernalization

FLC is repressed, lifting its inhibition on flowering genes.

Stratification

A cold treatment of seeds to break dormancy and promote germination.

Essential elements for plant growth

17 essential elements.

Essential micronutrients

Iron (Fe), Manganese (Mn), Zinc (Zn), Copper (Cu), Molybdenum (Mo), Boron (B), Chlorine (Cl), and Nickel (Ni).

Calcium deficiency effects in plants

Causes necrosis in young tissues, poor root growth, and disorders like blossom-end rot.

ABC layers of soil

A horizon: Topsoil, B horizon: Subsoil, C horizon: Parent material.

Hormone promoting seed germination

Gibberellin (GA) promotes seed germination.

Hormone preventing seed germination

Abscisic acid (ABA) prevents seed germination.