The most important colors in regulating photomorhogenesis in plants are:
1. Violet and Yellow
2. White and Black
3. Green and Orange
4. Red and Blue

Blue light photoreceptors in plant do not regulate:
1. Phototropism
2. Light induced opening of stomata
3. Light induces slowing of hypocotyls elongation
4. Seed germination

The biologically active form of the phytochrome is:
1.${\mathrm{P}}_{\mathrm{r}}$
2. ${\mathrm{P}}_{\mathrm{fr}}$
3. Both
4. None

When lettuce seeds illuminated by red light are then exposed to far red light:

1. ${\mathrm{P}}_{\mathrm{r}}$ is converted to ${\mathrm{P}}_{\mathrm{fr}}$ and germination is inhibited
2. ${\mathrm{P}}_{\mathrm{r}}$ is converted to ${\mathrm{P}}_{\mathrm{fr}}$ and germination is initiated
3. ${\mathrm{P}}_{\mathrm{fr}}$ is converted to ${\mathrm{P}}_{\mathrm{r}}$ and germination is inhibited
4. ${\mathrm{P}}_{\mathrm{fr}}$ is converted to ${\mathrm{P}}_{\mathrm{r}}$ and germination is initiated

Light passing through the green leaves of canopy trees above a seed:
1. stimulates its germination
2. inhibits its germination
3. does not affect its germination
4. causes abnormal germination in the seed

Etiolated seedlings become normal when exposed to:
1. Blue light
2. Green light
3. Red light
4. Far red light

Flowering will take place in a short day plant only when:
1. days are shorter than nights.
2. days are shorter than a certain critical value.
3. nights are shorter than a certain critical value.
4. nights are longer than a certain critical value.

A short day plant is exposed to a flash of red light followed by a flash of far-red light given during the middle of the night. The expected effect is that this will:
1. cause increased flower production.
2. have no effect upon flowering.
3. inhibit flowering.
4. stimulate flowering.

An incandescent light bulb has a high output of red light. Which of the following plant process will be least promoted by it:
1. photosynthesis.
2. seed germination.
3. phototropism.
4. flowering.

The level of the biologically active ${\mathrm{P}}_{\mathrm{fr}}$ form of phytochrome will be reduced by all the following except:
1. exposure to far-red light
2. exposure to red light
3. long dark period
4. destruction of phytochrome