Plant hormones

Plant hormones

not directly involved in metabolic or developmental processes but they act at low concentrations to modify those processes.

Plant hormones

chemical messengers that mediate intercellular (between cells) communications

Growth stimulators

involved in cell division, cell elongation, organ initiation, differentiation (ex. auxins, gibberellins, cytokinins)

Growth inhibitors or antagonists to known stimulators

involved in senescence, abscission, flower fading, fruit ripening

• abscisic acid (ABA)

• ethylene

• protein

• signal transduction

• enzyme

• gene expression

Mechanism by which hormones act at the cellular level

the hormone must first bind to a _________ receptor (either on the cell surface or inside the cell)

activates a _____ _______ pathway

leads to changes in ______ activities, ion gradients, ____ _______

indole-3-acetic acid (IAA)

primary auxin present in plants

AUXIN

• Discovered as substance associated with phototropic response.

• Cell elongation, root and shoot development

• flower initiation

• sex determination

• fruit development

Provide 3 additional responses to Auxin

cell elongation

Auxin exhibits induction of ___ ________

apical dominance

Auxin promotes _____ _______ by inhibiting lateral bud formation

seedless fruits

Auxin regulates fruit development of _____ fruits (parthenocarpy )

• phototropism

• geotropism

Regulates tropic responses such as

shoot apical meristem

Auxins are produced primarily in ____ ______ ______

lateral root growth

Auxins stimulate _____ _____ _____ and root initiation on stem cuttings

polar transport

Auxins move through the plant by ____ transport

parenchyma cells

Auxin movement by polar transport

Unidirectional movement down the stem through ________ ____

the vascular tissue

Auxin movement by polar transport

Auxin does NOT travel through _____ _____

apical dominance

Auxins inhibit lateral bud sprouting. This is called _____ _____

Cytokinins

- Produced mainly in roots; travels through the xylem

- Derived from the nucleotide adenine

cytokinesis

Auxin regulates DNA replication while cytokinin regulates ______

root

⬆Auxin + ⬇ cytokinin = ______ formation

shoot

⬆ cytokinin + ⬇ auxin = ______ formation

⬆ auxin

⬆cytokinin

- lateral bud repression, apical dominance

- lateral bud development, apical repression

Etiolated leaves exposed to cytokinin

________ … show extensive grana formation and chlorophyll synthesis

⬆Cytokinins

⬇Auxins

development of axillary or adventitous buds

(clue: ↘↖↗↔↘↖)

⬆Auxin

⬇Cytokinin

the rooting of the shoots

(clue: ↖↗↔↘)

Gibberellins

cause of "foolish seedling"

terpenoid pathway

Gibberellins

Derived from the ____ ____

embryonic tissues (meristems)

Gibberellins

Produced in ____ ____ (___)

non-polar

Gibberellins

Transportation is _________, bidirectional producing general responses.

Abscisic Acid

- Synthesized in plastids from carotenoids

- Derived from terpenoid pathway

Abscisic Acid

• promotes seed dormancy by inhibiting cell growth

• produced in response to stress

Ethylene

Formed from the amino acid methione

Ethephon

a commercial fruit ripener that breaks down to ethylene inside plant tissues