Hormones and Growth

What can development and growth of tissues depend on

internal conditions and external environment

What are the internal conditions that development of tissues depend on

heredity, age, and position

Growth vs differentiation

growth is cell division, whereas differentiation is specialization of cells via gene expression

What are induced changes

modifications to cells through the life

of the plant (e.g. preparation for winter)

What does development require

the coordination (mediated by signals) of cell activity with

the movement of resources.

What is totipotency

(or cell potency) is the ability of a cell to

differentiate into other cell types.

When are animal cells totipotent

early in the development of the zygote

What are plant horomones

substances that provide long-range signaling to

coordinate growth, development and response to

environmental stimuli. ( plant growth regulators)

What are target cells

those that are affected by the horomone

What occurs when the hormone binds the binding site of a target cell

increase of calcium in cytoplasm, which activates enzymes (gene expression…)

what are the 5 important plant hormones

auxins, gibberellin, cytokinin, ABA, and ethylene

What are auxins

A class of hormones that play an essential role in

regulating growth (e.g. lateral root growth) and

responses to the environment (gravitropism)

Where are auxins produced

in the shoot apical

meristems and in young leaves

What do auxins plat a key roll in

apical dominance that inhibits growth of axillary buds, as well as phototropism and gravitropism

What is phototropism

movement with respect

to light sources

What is gravitropism

movement with respect

to direction of gravitational forces

What do phototropism and gravitropism do

respond to the environment, initiates later roots and promotes xylem differentiation

What is gibberellin

a hormone shared by plants and fungi, discovered by Japanese physiologists studying rice

Where is gibberellin produced

in shoot apical meristem and young

leaves, as weel as in the embryo

What key roles does gibberellin play

• Plays a key role in the division and elongation of cell in

the internode areas.

• In addition, gibberellins promote germination of

dormant seeds

• Promotes phloem differentiation

What is cytokinin

A class of plant hormones that often play a

complementary role to auxins

Where is cytokinin produced

root apical meristem and developing fruits

What is cytokinins main function

to promote cell division, and divert nutrients towards areas with high concentration

Where is ABA produced

leaves and ovules

What does ABA do

increase as water decreases –

prompting several responses including the

closure of the stomata

What does ABA play a key role in

preventing seed

germination and promoting dormancy. Higher

ABA levels in the seeds:

- allows them to survive low water conditions

- prevents premature germination

What is ethylene

a hormone that exists as a gas in normal conditions

Where is ethylene produced

in damaged (wounded or aged) tissue

What are the key functions to ethylene

induce fruit ripening, signal for leaf and flower senescence, and root hair formation

What hormone balances out auxins in homeostasis

cytokinin as it stimulates leaf or axillary bud growth, while auxins stimulate root growth

What hormone balances out gibberellins in homeostasis

ABA as it inhibits growth until conditions improve, while gibberellin promotes growth