After a plant is set on a windowsill for several days, it’s owner comes back to find its stem bent at a sharp angle toward the glass window. which of the following describes this movement of the plant in response to stimuli?

a. gravitropism
b. thigmotropism
c. negative phototropism
d. positive phototropism

D. + phototropism

Explanation:

This is due to accumulation of harmone auxin on the tip of the stem.

This harmone accumulate on that part where light comes.

D. positive phototropism

Explanation:

Tropism is a response shown by the plant towards an external stimulus like gravity, light, touch and water. The phototropism can be define as a response shown by the plant towards the sunlight. The positive phototropism can be shown when a plant part bends towards the incident beam of sunlight. This is typically shown by aerial parts like stems and leaves. The negative phototropism is shown by the roots which grow underground they do not require sunlight.

According to the given situation, the plant is showing the response towards the sunlight stimuli by bending therefore, it is an example of positive phototropism.

these muscles maintain the blood pressure in the vessels. the smooth muscles are innervated by nerves of the autonomic nervous system. when the muscles contract, they cause vasoconstriction of the vessels and increase blood pressure. when the muscles relax, they enable vasodilation of the   blood vessels hence reduce blood pressure.