19.How do guard cells regulate opening and closing of stomatal pores?
(b) Two similar green plants are kept separately in oxygen free containers, one in
dark and the other in continuous light. Which one will live longer? Give reasons.
(a)Leaves of a healthy potted plant were coated with vaseline. Will this plant
remain healthy for long? Give reasons for your answer.
(b)What will happen to the rate of photosynthesis in a plant under the
following circumstances?
(i) cloudy day in morning but bright sunshine in the afternoon.
(ii)no rainfall in the area for a considerable time.
(iii) gathering of dust on the leaves.
Answers
19.The guard cells regulate the opening and closing of stomatal pores by the osmosis process. When water flows into the guard cells, they swell up and the curved surface causes the stomata to open. When the guard cells lose water, they shrink and become flaccid and straight thus closing the stomata.
b.Plant kept in continuous light will live longer, because it will be able to produce oxygen required for its respiration by the process of photosynthesis.
a.The Leaves of a healthy plant coated with Vaseline would not stay healthy because Vaseline coating will block the stomata. ... Hence the process of transpiration, photosynthesis and respiration stops and the plant will not remain healthy and would die slowly.
b.Cloudy days the rate of photosynthesis will decrease because sunlight is necessary for photosynthesis. On a cloudy day, there will be less sunlight. ... Good manuring in the area will increase the amount of these minerals in the soil thus increasing photosynthesis.
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Answer:
(a) The guard cells regulate the opening and closing of stomatal pores by the osmosis process. When water flows into the guard cells, they swell up and the curved surface causes the stomata to open. When the guard cells lose water, they shrink and become flaccid and straight thus closing the stomata.
(b) Plant kept in continuous light will live longer, because it will be able to produce oxygen required for its respiration by the process of photosynthesis.
(a) The Leaves of a healthy plant coated with Vaseline would not stay healthy because Vaseline coating will block the stomata. In a plant, there will be no intake of carbon dioxide from the surrounding to carry out the process of photosynthesis because the pores of stomata are blocked by the Vaseline.
(b) Photosynthesis is a process of formation of "carbohydrates and oxygen" in plants with the help of carbon dioxide gas and water. The reaction occurs in the "sunlight and chlorophyll" presence in the leaves of plant.
(i) In cloudy day, the sunlight will be less, hence, the rate of photosynthesis will decreases.
(ii) If there is "no rainfall" in the area, then there will be no water. Hence, it will not be available for photosynthesis and leaves will also be dry, so there is less chlorophyll. Hence, photosynthesis rate will decrease.
(iii) Manures provide nutrients to plants hence rate of photosynthesis will increase.
(iv) Stomata helps to transfer gas for photosynthesis. Hence, due to blocked stomata, photosynthesis rate will decrease.