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Photosynthesis · Maharashtra Board STD 11 Science (MSBSHSE - English Medium). 3 questions.

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Question 13 Marks
nature of light.
Answer
  1. Light is a form of energy.
  2. It travels as stream of tiny particles called photons.
  3. A photon contains a quantum of light.
  4. Light has different wavelengths having different colors.
  5. One can see electromagnetic radiation with wavelengths ranging from 390nm to 730nm. This part of the spectrum is called the Visible light.
  6. It lies between wavelengths of ultraviolet and infra-red.
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Question 23 Marks
Crassulacean Acid Metabolism.
Answer
Crassulacean Acid Metabolism $\text{(CAM).}$
$1.$ It is one more alternative pathway of carbon fixation found in desert plants.
$2.$ It was first reported in the family Crassulaceae, therefore called as $\text{CAM}($Crassulacean Acid Metabolism$).$
$3.$ In $\text{CAM}$ plants, stomata are scotoactive i.e. active during night, hence initial $CO_2$ fixation occurs in night.
$4.$ Thus, $C_4$ pathway fix $CO_2$ at night and reduce $CO_2$ in day time via the $C_3$ pathway by using $\text{NADPH}$ formed during the day.
$5. \  \text{PEP}$ caboxylase and Rubisco are present in the mesophyll cell $($no Kranz anatomy$).$
$6.$ Formation of malic acid during dark is called acidification $($phase $I).$
$7.$ Malate is stored in vacuoles during the night.
$8.$ Malate releases $CO_2$ during the day for $C_3$ pathway within the same cell is called deacidification $($phase $II).$
$9.$ Examples of $\text{CAM}$ plants: Kalanchoe, Opuntia, Aloe etc.
$10.$ The Chemical reactions of the carbon dioxide fixation and its assimilation are similar to that of $C_4$ plants.
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Question 33 Marks
Kranz Anatomy of a $C_4$ plant.
Answer
1$.$ Anatomy of leaves of $C_4$ plants is different from leaves of $C_3$ plants.
$2. \ C_4$ plants show Kranz anatomy.
$3.$ In the leaves of such plants, there is a bundle sheath around the vascular bundles.
$4.$ The chloroplasts in the bundle $–$ sheath cells are large and without or less developed grana, where as in the mesophyll cells the chloroplasts are small but with well$-$developed grana.
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