16.1 Plant Hormones And Growth In Plants

Question 1

What are the roles of auxins in plants?

Answer 1

Cell elongation
Apical dominance
Root growth

Question 2

How do auxins play a role in cell elongation?

Answer 2

The cell wall increases in stretchiness, enabling water absorption and and cell expansion

Experimental evidence:
Auxin application causes pH to decrease
Enzymes that increase cell wall flexibility work best in acidic conditions

Question 3

How do auxins play a role in apical dominance?

Answer 3

They promote the growth of the main shoot and inhibits lateral shoots

Experimental evidence:
Lateral shoots grow faster when the apex of the main shoot (the set of auxin production) is removed

Question 4

How do auxins play a role in root growth?

Answer 4

Low auxin concentrations promote root elongation

Experimental evidence:
Application of small quantities of auxin stimulates root growth; high concentrations inhibit growth

Question 5

What are the roles of gibberellins in plants?

Answer 5

Stem elongation

Seed germination

Question 6

How do gibberellins play a role in stem elongation?

Answer 6

The stimulate cell elongation and division

Experimental evidence:
Gibberellin concentrations and plant height show positive correlation

Question 7

How do gibberellin play a role in seed germination?

Answer 7

They activate genes for amylase and protease enzymes which break down food and stores in seeds

Experimental evidence:
Mutant seeds that lack gibberellin genes and seeds exposed to gibberellin inhibitors do not germinate

Question 8

What are the roles of ethene in plants?

Answer 8

Promote leaf fall (abscission)

Promote fruit ripening