Question : A portion of cross section of leaf is shown in the diagram. Answer the following:- A) Label 1 to 4. B) What kind of anatomy is shown in the diagram ? C) Write the structure and function of 2 and 4.

Question : A portion of cross section of leaf is shown in the diagram.

1.	Question : A portion of cross section of leaf is shown in the diagram. Answer the following:- A) Label 1 to 4. B) What kind of anatomy is shown in the diagram ? C) Write the structure and function of 2 and 4.
Answer» Solution :A) 1). Mesophyll cells 2) Mesophyll chloroplasts 3) Cells of bundle shealth. 4) Bundle sheath chloroplasts. B) Kranz anatomy. This kind of anatomy occurs in the LEAVES of `C_(4)` PLANTS in whichthe bundle-sheath cells are arranged in a wreath-like manner. C) Structure and function of 2. Mesophyll chloroplasts: Mesophyll chloroplasts are granal and contain thylakoids that are stacked to form grana. These chloroplasts PERFORM LIGHT reaction with the evolution of molecular `O_(2)`. The `CO_(2)` is fixed by phospho enol pyruvic acid to form 4 carbon oxalo acetic acid. 4. Bundle sheath chloroplasts are agranal, i.e., grana are absent and the thylakoids are present only as stroma lamellae. Bundle sheath chloroplasts perform `C_(3)` cycle in which the `CO_(2)` is fixed by RuBP catalysed by the enzyme RUBISCO (RuBISCO is present only in bundle sheath chloroplasts). `CO_(2)` is made available by DECARBOXYLATION of 4 carbon organic acid (malic acid).