Plant Hormones

Question 1

Plant hormones are produced in?

Answer 1

very low concentration

Question 2

Hormones control?

Answer 2

plant growth and development

-by affecting the division, elongation and differential of cells

Question 3

What is auxin used for?

Answer 3

used for any chemical substance that promotes cell elongation in different target tissues

Question 4

Major role in the growth response of cells to auxin?

Answer 4

proton pumps

-according to acid growth hypothesis

Question 5

cell elongation in response to auxin?

Answer 5

1. auxin increases the activity of proton pumps
2. the cell wall becomes more acidic
   3.Wedge-shaped expansions, activated by low pH, separate cellulose microfibrils from cross-linking polysaccharides. The exposed cross-linking polysaccharides are now more accessible to cell wall enzymes.
   4.The enzymatic cleaving of the cross-linking polysaccharides allows
   the microfibrils to slide. The extensibility of the cell wall is increased. Turgor causes the cell to expand.
3. with the cellulose loosened, the cell can elongate.

Question 6

Role of auxin in lateral and adventitious root formation?

Answer 6

involved in the formation and branching of roots

Question 7

auxin as?

Answer 7

• herbicides

- overdose of auxins can kill eudicots

Question 8

auxin in secondary growth?

Answer 8

-by inducing cell division in the vascular cambium and influencing differentiation of secondary xylem

Question 9

cytokinins?

Answer 9

• stimulate cell division
• produced in actively growing tissues
• roots, embryo, fruits
• work together with auxin

Question 10

factor of control of apical dominance?

Answer 10

• cytokinins
• auxin
• ability of a terminal bud to suppress development of axillary buds

Question 11

cytokinins: control of apical dominance

if the terminal bud is removed

Answer 11

plant become bushier

Question 12

cytokinins: anti aging effect

Answer 12

retard the aging of some plant organs

Question 13

cytokinins: anti aging effect how?

Answer 13

• by inhibiting protein breakdown
• stimulationg RNA and protein synthesis
• mobilizing nutrients from surrounding tissues

Question 14

why do florist use cytokinins?

Answer 14

to keep cut flowers fresh

Question 15

gibberellins can effect?

Answer 15

• stem elongation
• fruit growth
• seed germination

Question 16

gibberellins: stem elongation

Answer 16

gibberellins stimulate growth of both leaves and stems

-in stems, gibberellins stimulate cell elongation and cell division

Question 17

gibberellins: fruit growth

Answer 17

• auxin and gibberellins must be present for fruit to set

- gibberellins are used commercially (@spraying of Thompson seedless grapes)

Question 18

effect of abscisic acid?

Answer 18

1. seed dormancy

2. drought tolerance

Question 19

abscisic acid: seed dormancy

Answer 19

• ensure the seed will germinate only when there are optimal condition
• high level of ABA in maturing seeds inhibit germination and induce production of certain proteins ( help to withstand extreme dehydration)

Question 20

abscisic acid: drought tolerance

Answer 20

-ABA is the primary internal signal that enables plants to withstand drought
-when plant begin to wilt,
ABA accumulates in leaves and causes stomata to close rapidly (to reduce transpiration, prevent water loss)

Question 21

why plants produces ethylene?

Answer 21

-response to stresses
such as
-drought
-flooding 
-mechanical pressure
-injury
-infection

Question 22

ethylene: apoptosis

Answer 22

burst of ethylene :

1. cells
2. organs
3. whole plant

Question 23

ethylene: leaf abscission

Answer 23

• change in the balance of auxin and ethylene controls leaf abscission
• process that occurs in autumn when a leaf falls

Question 24

ethylene: fruit ripening

Answer 24

A burst of ethylene production in the fruit
•Triggers the ripening process
•Enzymatic breakdown of cell wall component
softens the fruit
•Conversion of starches and acids to sugar
makes the fruit sweet

Question 25

where auxin is found in plant?

Answer 25

embryo of seed, meristems of apical buds, young leaves

Question 26

where cytokinins is produced?

Answer 26

synthesized in roots and transported to other organs

Question 27

where gibberellins is produced?

Answer 27

meristems of apical buds and roots, young leaves, embryo

Question 28

where is abscisic acid is produced?

Answer 28

leaves, stems, roots, green fruit

Question 29

where is ethylene is produced or found in a plant?

Answer 29

tissues of ripening fruit, nodes of stems, aging leaves and flowers