Through their effect on plant growth regulators, what do the temperature and light control in the plants?

1. Flowering 

2. Closure of stomata

3. Fruit elongation 

4. Apical dominance 

Photoperiodism was first characterized in:

1. tobacco

2. potato

3. tomato

4. cotton

The wavelength of light absorbed by Pr form of phytochrome is:

1. 640 nm

2. 680 nm

3. 720 nm

4. 620 nm