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4. Are the following statements true or false? Give reason in support of your answer.
Biology | Class 10 | ICSE | Photosynthesis | Selina
4. Are the following statements true or false? Give reason in support of your answer.

(a) The rate of photosynthesis continues to rise as long as the intensity of light rises.

(b) The outside atmospheric temperature has no effect on the rate of photosynthesis.

(c) If you immerse a leaf intact on the plant in ice cold water, it will continue to photosynthesize in bright sunshine.

(d) Destarching of the leaves of a potted plant can occur only at night.

(e) The starting point of carbon cycle is the release of CO2 by animals during respiration.

(f) If a plant is kept in bright light all the 24 hours for a few days, the dark reaction (biosynthetic phase) will fail to occur.

(g) Photosynthesis is considered as a process supporting all life on earth.

Solution :

  • The rate of photosynthesis continues to rise as long as the intensity of light rises.

Answer : false

The rate of photosynthesis increases with the intensity of light but upto a certain limit after that it gets fixed at that certain point .

  • The outside atmospheric temperature has no effect on the rate of photosynthesis

Answer : false

Outside temperature effects the rate of photosynthesis . With the increase in temperature the rate of photosynthesis also increases . This rise occurs up to the maximum temperature of 35°C , after which falls and stops above 40 Co.

  • If you immerse a leaf intact on the plant in ice cold water, it will continue to photosynthesize in bright sunshine

Answer : false

For rate of photosynthesis  temperature is a necessary factor . Even in presence of bright sunlight ice cold water will hamper the rate of photosynthesis in the leaf .

  • The starting point of carbon cycle is the release of CO2 by animals during respiration

Answer : false

For the experiment of photosynthesis the plant which is used should be placed in dark  for 24 to 48 hours only . During this time  period the starch will be removed from the leaves and will be stored in the storage organs .

  •    The starting point of carbon cycle is the release of CO2 by animals during respiration

               Answer :  false

               There is no starting and ending point of carbon cycle . In the atmosphere carbon is

                present by respiration and combustion .

  •  If a plant is kept in bright light all the 24 hours for a few days, the dark reaction (biosynthetic phase) will fail to occur.

Answer : false

If a plant is kept in bright light all the 24 hours for a few days, the dark reaction (biosynthetic phase) will continue to occur , because the reaction is not dependent of light .

  • Photosynthesis is considered as a process supporting all life on earth.

Answer : true

Photosynthesis is the source of food and energy for all living organisms . For animals it is directly and for human beings it is indirectly . Thus we can say that photosynthesis is considered as a process supporting all life on earth.

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