plant responses

Question 1

role of auxins in phototropism

Answer 1

phototropism a growth response towards or away from light. can be positive or negative. if a plant grows towards the light, it is positively phototropic. if a plant grows away from the light, it is negatively phototropic.

Question 2

role of auxins in gravitropism

Answer 2

gravitropism is a growth response towards or away from gravity. if a plant grows upwards, it is positively gravitropic. if a plant grows upwards, it is negatively gravitropic. Auxins cause cell elongation in the shoot, but inhibit cell growth in the root. In roots, auxins are positively gravitropic, and are therefore situated at the bottom layer of the root. The top layer therefore grows faster, pushing over the bottom layer and growing downwards towards gravity. The root is therefore positively gravitropic.

Question 3

gibberellins

Answer 3

gibberellins are plant hormones that increase internodal growth. They are responsible for elongating internodes (the space between two nodes)

Question 4

absciscic acids

Answer 4

• responsible for fruit ripening and colour changing
• responsible for leaf dropping (leaf senescence)
• slows down plant metabolism and prepares plant for dormancy
• maintains dormancy in seeds (useful for seed banks in agriculture)