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IPE Senior Inter Botany SA Important Questions

1. Succulents are known to keep their stomata closed during the day to check transpiration. How do they meet their photosynthetic CO2 requirements?
A. Succulents show CAM pathway. They show light reaction during day time and dark reaction in the night. Thus they get photosynthetic CO2 requirements from light reaction that occurs during day time.

2. Chl-a is the primary pigment for light reaction. What are accessory pigments? What is their role in photosynthesis?
A. The primary pigment for light reaction is Chl-a. It converts radiant energy to chemical energy The other pigments which include Chl b and carotenoids (carotenes and Xanth ophylls) are accessory pigments. Their functions are..
1) They absorb light and transfer it to Chl-a
2) They enable a wide range of wavelength of incoming light to be utilised for photosynthesis
3) They protect Chl-a from photo oxidation or photo bleaching or Solarisation

3. Does 'dark reaction' of photosynthesis require light? Explain
A. Dark reaction do not requires light but it needs the product formed in light reaction. Hence it occurs also during day time.

4. How are photosynthesis and respiration are related to each other?
A. Photosynthesis is the source of food and oxygen which are essential and form the basis of life. The oxygen released in it is taken by living organisms (animals) and release CO2. This CO2 in turn taken by the plants. Priestly was the first to propose that green plants take toxic gases released by animals in respiration and
release pure gas (O2) Photosynthesis is anabolic and respiration is catabolic

5. In what type of plants do you come across 'Kranz' anatomy? To which conditions are those plants better adapted? How are these plants letter adapted than the plants, which lack this anatomy?
A. We come across Kranz anatomy in the plants with following characters.
1. Mostly grasses
2. The leaves are isobilateral
3. Mesophyll is undifferentiated
4. Bundle sheath cells are big and arranged circularly in the form of a wreath
5. Leaves show chloroplast dimorphism. These are better adapted to high light intensity, high carbondioxide concentration, high temperature. The plants which lack this anatomy are not adapted to such conditions. These plants have both RuBP case (bundle sheath cells) and PEP case (mesophyll cells) and do not show photo respiration.

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