Plant responses

Question 1

Function of auxins

Answer 1

Cell elongation, prevention of leaf abscission, maintaining apical dominance, tropisms stimulate ethene

Question 2

Function of gibberelins

Answer 2

Stem elongation, mobilisation of food stores in seed germination, pollen tube growth

Question 3

Function of ethene

Answer 3

Fruit ripening, promotes leaf abscission

Question 4

Function of ABA

Answer 4

maintains seed dormancy, antifreeze responses and stomatal closing

Question 5

Seed germination

Answer 5

Seeds absorb water which activates gibberlins, these then make enzymes that cause the break down of food stores. Food stores then used to make ATP which provides energy to break down seed coat

Question 6

How does ABA affect germination

Answer 6

acts as antagonist hormone and relative levels of gibberelins to ABA determines plant germination

Question 7

How do auxins affect plant growth

Answer 7

Auxins made in cells at the tips of roots and shoots and in meristems can move up/down the plant via transport tissue from cell to cell. Affects plasticity of cell wall. Binds to the receptors of plant membranes causing the PH to fall to around 5 where the plasticity is highest and when the cell matures auxins die and PH rises cell becomes rigid

Question 8

How do auxins affect lateral growth/ roots

Answer 8

High conc of auxins supress lateral growth of shoots but grows quickly in the main shoot. Further down the stem there is lower conc of auxin so more lateral growth toward the base.
Low conc of auxin promote root growth

Question 9

What is abiotic stress

Answer 9

changes in the environment which cause plant response

Question 10

Why do leaves fall off

Answer 10

During colder months the amount of glucose required for respiration to maintain leaves and produce antifreeze properties from cholorophyll is greater than the amount produced in leaves, fall off to conserve energy.

Question 11

Photoperiodism

Answer 11

Plants that are sensitive to the lack of light in their environment affected by phytochrom pigments

Question 12

Abscission definition

Answer 12

Lengthening of dark periods causes abscission

Question 13

Abscission process

Answer 13

falling light levels decrease in auxin concentration , this cause ethene to be produced. In the abscission zone (base of stalk) 2 layers sensitive to ethene. Vascular bundle sealed off by fatty material. cells in separation zone respond to hormones by swelling, weakening it. Callose digests cell wall in abscission zone which separates petiole from stem