 |
| 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.
Read more:
http://wiki.answers.com/Q/Why_does_stomata_close_at_night_and_open_during_the_day#ixzz1x7TOxCFr
 |
| 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.
