Thursday, June 7, 2012

Question and answer about STOMATA

An opening stomata of a tomato leaf

Question 1 : Why does the stomata close during hot weather?

Answer :
Stomata, also known as stoma, close in hot weather to retain water. Even though open stoma are necessary for photosynthesis, they can dry out a plant. About 90% of water absorbed by a plant is lost through open stoma. The guard cells close the entrance for protection against dehydration.

Question 2 : Why does stomata close at night and open during day?

Answer :
Some Stomata close at night because of the heat, while others open at night because of the moisture. CAM plants such as cacti and pineapple open their stomata at night so that the moisture in the air can be absorbed. CAM plants are adapted to hot, dry environments such as deserts, so opening at day would just evaporate any water that the plant had absorbed. So CAM plants open at night and close at day, while plants adapted to environments such as the ones in forest open at day and close at night.

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An opening stomata of rose plant
Question 3 : SO, does stomata close or open during hot weather?

Answer (i):
There are multiple parts and functions of the stomata that work during the process of photosynthesis. The specialized guard cells in the stomata of plants are called guard cells; the most important part to the stomata. Guard cells control opening and closing of the pores in the response of the environment (Shuppan). They are undersurface of leaves for controlling gas exchange and water loss of the plant. Guard cells are in pairs and shaped like a kidney bean so that stomata can exist between them. During warm weather, when a plant is likely to lose excessive water the guard cells close eliminating as much water evaporation from the interior of the leaf. 

Answer (ii) :
These stomata structures alter in size according to their turgor, which is mostly determined to the water concentration in them. When water concentration drops in the stroma areas, the opening to the external environment closes. Stomata therefore play a regulating role in the homeostasis of water control. During a particular hot day, while the stomata is open for photosynthesis, transpiration can occur at a much higher rate due to the temperature. When this occurs, the water concentration drops in the stomata and therefore it loses turgor, and in turn the stomata opening closes. This ensures that water concentration is kept near its preferred level. This type of water transpiration occurs in mesophyte plants, which occupy climates that are of average rainfall and of average temperature.
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