Question

1.

Under the canopy of the taller trees live other plants at the forest floor.  Most of the light that reaches the leaves of the plants on the forest floor is in the far-red wavelengths rather than the red wavelengths. Why?

The leaves above reflect most of the green light.

Carotenoids in the leaves above absorb the red light.

Chlorophyll in the leaves above absorbs the red light.

Ethylene contributes to the shade avoidance process.

2. If mostly far-red light reaches these lower leaves described in Question 1, what type of growth is likely to predominate in these plants? (P_fr is responsible for stimulating branching and inhibiting vertical growth.)

vertical growth

horizonatal/branching growth

3.

The hormone that is most active in helping this type of growth in the plants in Question 2 is

cytokinins

auxin

Answer 1

1) Most of the light that reaches the leaves of the plants on the forest floor is in the far-red wavelengths rather than the red because the chlorophyll in the leaves above absorb the red light. The carotenoids absorb blue violet region while chlorophyll absorbs blue and red region reflecting green light. So , only the far red , which is not absorbed by the chlorophyll reaches the forest floor along with green light.

2) If mostly far-red light reaches these lower leaves described in Question 1 , the vertical growth is likely to predominate in these plants. As in Far red region , the Pfr converts into Pr which slows growth and inhibits plant 's horizontal growth and branching.

3) Vertical type of growth is stimulated by auxin hormone. Cytokinin hormone stimulates the branching in plant.