Question

Leaves of green plants contain openings known as stomates, which are opened and closed by specialized cells allowing for gas exchange between the leaf and the outside environment. Which phrase best represents the net flow of gases involved in photosynthesis into and out of the leaf through these openings on a sunny day?
A. Carbon dioxide moves in; oxygen moves out
B. Carbon dioxide and oxygen move in; ozone moves out
C. Oxygen moves in; nitrogen moves out
D. Water and ozone move in; carbon dioxide moves out

Answer 1

Answer:

A. Carbon dioxide moves in; oxygen moves out

Explanation:

Stomata are small pores on the leaves of green plants whose opening and closing is regulated by the surrounding guard cells.

During the day, solutes from surrounding cells enter the guard cells leading to reduction in the water potential of the cells. Consequently, water enters the guard cells and makes them turgid, leading to the opening of the stomatal pores.

At nights, the solutes in the guard cells move back to the surrounding cells, leading to loss of water and flaccidity of the cells. The guard cells collapse against one another, leading to the closure of the stomatal pores.

When stomata opens, carbon dioxide diffuses in and it becomes utilized in the process of photosynthesis. The resulting oxygen from photosynthesis then diffuses out through the stomatal pores.

Answer 2

Answer:

Carbon dioxide moves in; oxygen moves out

Explanation:

The pigment that offers the green pigmentation for green plants is known as Chlorophyll. On the surface of the leaves on green plants are microscopic openings known as Stomata in the epidermis of leaves. Stomata are generally more numerous on the underside of leaves. They provide for the exchange of gases between the outside air and the branched system of interconnecting air canals within the leaf.

On a sunny day, The concentration of carbon dioxide in the air is a regulator of stomata opening in many plants. The stomata opens (then  Carbon dioxide moves in and in-turn releases oxygen after photosynthetic activities has taken place) and closes in response to the internal pressure of two sausage-shaped guard cells that surround it. The inner wall of a guard cell is thicker than the outer wall.

The main function of these Guard cells  are to control excessive water loss, closing on hot, dry, or windy days and opening when conditions are more favourable for gas exchange.