lecture 7

Question 1

what is etiolation?

Answer 1

morphological adaptations for growing in darkness, such as a potato growing in darkness will produce unhealthy looking shoots and lacks elongated roots

Question 2

what happens when a plant experiences de-etiolation?

Answer 2

stem elongation slows, leaves expand, roots elongate, and the shoot produces chlorophyll

Question 3

what are the stages of cellular signaling

Answer 3

reception, transduction, response

Question 4

what is reception?

Answer 4

a hormone or environmental stimulus interacts with a receptor protein in the plasma membrane

Question 5

what is transduction?

Answer 5

relay proteins are activated as well as second messengers that pass the signal

Question 6

what is response?

Answer 6

the passed signal ultimately activates cellular responses

Question 7

what is the receptor in de-etiolation?

Answer 7

phytochrome, which is capable of detecting light. it is located in the cytoplasm

Question 8

what are the 2 types of second messengers in de-etiolation

Answer 8

1. Ca2+ ions
2. cyclic G MP (cGMP)

Question 9

the phytochrome receptor responds to light by: (2)

Answer 9

opening Ca2+ channels, which increases Ca2+ levels in cytosol
and activating an enzyme that produces cGMP

Question 10

what is post translational modification?

Answer 10

involves modification of existing proteins in the signal response

Question 11

what are the 5 major types of plant hormones

Answer 11

Auxin, Cytokinins, Gibberellins, Abscisic acid, Ethylene.

( the others are brassinosteroids, jasmonates, and strigolactones)

Question 12

what is a tropism?

Answer 12

any growth response resulting in turning of all or part of an organs toward or away from a stimulus is a tropism. in short, its a growth response

Question 13

what is auxin?

Answer 13

refers to any chemical that promotes elongation of coleoptiles

Question 14

what is the major auxin in plants?

Answer 14

indoleacetic acid (IAA)

Question 15

where is auxin produced?

Answer 15

produced in the shoot tips and is transported down the stem. it only moves from tip to base. this is called polar transport

Question 16

what do auxin transporters do?

Answer 16

move the auxin out of the cell. so that the auxin can then enter the apical end of the next cell.

Question 17

what is the acid growth hypothesis?

Answer 17

auxin stimulates/increases proton pumps in the plasma membrane, which lower the pH of the cell wall, activating expansins and enzymes that loosen the cellulose, with cellulose loosened the cell can elongate. auxin alto alters gene expression to stimulate a sustained growth response.

Question 18

what are the major functions of auxin?

Answer 18

increases plasticity of cell wall
promotes elongation of shoots and formation of lateral and adventitious roots.
regulates development of fruits.
enhances apical dominance.
affects secondary growth by inducing cell division in the vascular cambium & influencing differentiation of secondary xylem

Question 19

what are the practical uses for auxins?

Answer 19

the auxin IBA stimulates adventitious roots and is used in propagation of plant cuttings.
also, an overdose of auxin can kill plants, for EX, 2,4-D is used as a herbicide on eudicots

Question 20

what are cytokinins?

Answer 20

they stimulate cytokinesis

Question 21

where are cytokinins produced ?

Answer 21

in actively growing tissues such as roots, embryos and fruits

Question 22

how do cytokinins slow the aging of some plant organs how?

Answer 22

they inhibit protein breakdown, they stimulate RNA and protein synthesis. mobilize nutrients from surrounding tissues, and slow progress of apoptosis, which is programmed cell death

Question 23

if a terminal bud on a plant is removed, what would happen?

Answer 23

the plant would become bushier. allows the other buds to recieve more sugars for growth rather than it all going to the terminal bud

Question 24

what are gibberellins?

Answer 24

are hormones with a variety of effects, such as stem elongation, fruit growth, and seed germination

Question 25

where are gibberellins produced?

Answer 25

in YOUNG roots and leavesw

Question 26

fruit growth and hormones

Answer 26

just a general knowledge slide, not a question.

in many plants, both auxin and gibberellins must be present for fruit to actually develop

Question 27

how do gibberellins aid with germination?

Answer 27

after water is absorbed by a seed, gibberellins are released from the embryo and signals to the seed to start germinating.

Question 28

what is abscisic acid?(ABA)

Answer 28

the hormone that slows growth

Question 29

what are the affects of abscisic acid (ABA)?

Answer 29

effects seed dormancy- ensures seed will germinate only in optimal conditions. in some seeds, dormancy is broken if ABA is washed away by heavy rain, and low levels of ABA can cause early germination.
and drought tolerance- ABA is the primary signal that enables plants to withstand drought.

Question 30

what is ethylene?

Answer 30

ethylene is a gaseous hormone that can be produced by almost all parts of the plants in response to stresses such as drought, flooding, mechanical pressure, injury, infection.

Question 31

what are some of the responses that effect the effects of ethylene?

Answer 31

fruit ripening, mechanical stress, senescence, leaf abscission

Question 32

what is the triple response that is induced by ethylene?

Answer 32

the triple response allows growing shoots to avoid obstacles by slowing the stem elongation, thickening the stem and horizontal growth