Question

Which of the following statements is most correct?

a. phytochrome is a receptor protein that becomes phosphorylated when it receives far-red photons.
b. phytochrome is a receptor protein that changes shape and is an example of signal transduction.
c. plants can use the red:far red ratio to perceive the level of shade competition.
d. phytoporphyrin, also called phylloerythrin, is a molecule involved in signal transduction

Answer 1

The most correct statement is that phytochrome is a receptor protein that changes shape for signal transduction, allowing plants to sense environmental light conditions for growth regulation.

Step-by-step explanation:

The correct statement among the ones provided is that phytochrome is a receptor protein that changes shape and is an example of signal transduction. This occurs as a result of the absorption of red or far-red light which causes a significant alteration in the shape of the linear tetrapyrrole chromophore, leading to a change in the conformation and activity of the phytochrome protein. It's known that the physiologically active form of phytochrome, Pfr, is generated under red light and is converted back to the inactive Pr form under far-red light, with Pfr having the ability to activate or repress specific gene expression. Importantly, plants are able to sense their environment by using the red:far-red ratio, enabling them to detect the level of shade and thus competition from other plants, which is critical for their growth and survival.