Plant responses (8.6)

Question 1

State the name of the two phytochrome isomers

Answer 1

The two phytochrome isomers are phytochrome red and phytochrome far-red

Question 2

State which conditions cause phytochrome red to become phytochrome far red

Answer 2

In order to phytochrome red to convert to phytochrome far-red a plant must be in light conditions or in a source of red light. This is because during the day there is increased red light which allows for the conversion

Question 3

State which conditions cause phytochrome far-red to become phytochrome red

Answer 3

The reversion of phytochrome far-red to phytochrome red occurs when a plant is within darker conditions or around a source of far-red light

Question 4

State the differences between a short and long day plant

Answer 4

Short day plants require a longer period of darkness in order to germinate, during this period far-red is being reverted to red. However, long day plants require longer periods of day and light in order for germination to occur

Question 5

A long day plant is exposed to red light. Explain how red light causes a change in flowering gene expression in this plant

Answer 5

Long day plants require longer periods of light to germinate, such as during the day. The light contains red light which triggers phytochrome red to convert to phytochrome far-red. For long day plants phytochrome red stimulates growth and the transcription of growth factors

Question 6

A species of plant needs a minimum of 12 hours of darkness to stimulate flowering, is this a short or a long day plant?

Answer 6

This is an example of a short day plant as they require a critical length of darkness in order for flowering to be triggered. In this case the critical length is a minimum of 12 hours in which flowering csn occur, anything shorter and the plant would not flower