Plant Physiology When the radicle emerges from the seed, how does it know which
ID: 268478 • Letter: P
Question
Plant Physiology
When the radicle emerges from the seed, how does it know which direction it should grow? A) Like a Weeble that wobbles but does not fall down, or a cat that always lands on its feet, the seed 5) is balanced such that it usually falls to the ground in the correct orientation B) The direction of growth is not controlled and random probability contributes to which seedlings become established C) The radicle responds to light and demonstrates phototropism D) The radicle responds to gravity and demonstrates gravitropism E) The hypocotyl emerges first and homone gradients cause the ndicl to ow in h opposte direction Describe how auxin contributes to the direction of root growth- be sure to explain where the auxin levels are higher and lower in relation to that growth (2 pts) 6)Explanation / Answer
5) Option 'D' is the correct answer.
Radicle is the first part of seedling to emerge from the seed during the process of germination. The radicle is the embryonic root of the plant, and grows downward in the soil. It shows gravitropism and responds to gravity by growing downward. Hypocotyl is the embryonic stem that supports the cotyledons.
6) Auxins promote root initiation. As more native auxin is transported down the stem to the roots, the overall development of the roots is stimulated. If the source of auxin is removed, such as by trimming the tips of stems, the roots are less stimulated accordingly, and growth of stem is supported instead. Auxin plays an important role in the gravitropism of plant roots. Auxin transmits the gravity signal from sensing cells, that is, columella cells, to the root elongation zone. When gravity is sensed, auxin is transported preferentially to the lower side of the root, which leads to the accumulation of auxin in the elongation zone. When seedlings are treated with inhibitors of either auxin influx or efflux, gravitropism is severely inhibited.