Plants are able to remain cool during hot periods of the day because they _________ .

(1) shed their leaves
(2) close their stomata tightly
(3) exchange gases with their surrounding
(4) lose water vapour through their leaves and stem ( )

Can anyone please help out on this question ? Thanks.

Like humans plants sweat to keep cool. In plants this process is called transpiration which is the evaporation of water in plants. Therefore, from a P6 point of view I would choose 4).

Looking at the other options:
1) I think this option would result in plants not having leaves as they need to cool down so everyday they would be dropping their leaves. Also, leaves are required for making food.

2) Stomata are the pores in the plants leaves. Stomata open during the day light and close at night. Therefore, it is not logical considering plants would be hotter during the daytime.

3) Plants do exchange gases, through the stomata, however they do this for many reasons not just for transpiration.

4) The function of sweating (transpiration) is too cool the system down. Therefore, I would say this option.

Transpiration only occurs through the leaves via the stomata not the stem.
So I will choose 3)exchange gases with the surrounding.

my teacher told us that we can find stomata on stems as well. so transpiration should also occur on the stems.

A Science teacher gave me the following which am sure will help clarify:

Woody stems and mature roots are sheathed in layers of dead cork cells impregnated with suberin — a waxy, waterproof (and airproof) substance. So cork is as impervious to oxygen and carbon dioxide as it is to water.
However, the cork of both mature roots and woody stems is perforated by nonsuberized pores called lenticels. These enable oxygen to reach the intercellular spaces of the interior tissues and carbon dioxide to be released to the atmosphere.The photo shows the lenticels in the bark of a young stem.
In many annual plants, the stems are green and almost as important for photosynthesis as the leaves. These stems use stomata rather than lenticels for gas exchange.