Question

Anatomy of $C_4$ plant leaf shows-
A) Presence of peroxisomes
B) Presence of bundle sheath cells
C) Absence of mitochondria
D) Absence of bundle sheath cells.

Answer 1

Carbon fixation can be done by keeping carbon dioxide booked for it, rather than using it for photorespiration. $C_4$ plants require carbon dioxide to be available for Rubisco. For achieving this, carbon dioxide and rubisco are provided with separate compartments in the leaves.

Complete Answer:
Plants which are adapted to tropical dry regions have a $C_4$ pathway. They have special leaf anatomy in order to tolerate high temperature, high light intensities. The leaf anatomy in C4 plants is called kranz anatomy, it is derived from a German word which means wreath which is basically related to the arrangement of cells. In the leaves of $C_4$ plants, two rings of cells surround their vascular bundles; the inner ring is of bundle sheath cells, it contains chloroplasts lacking grana but rich in starch, the bundle sheath is impermeable for gases and does not have intercellular spaces. The outer ring is of mesophyll cells. Thus, the chloroplasts are called dimorphic. The primary function of such leaves is to provide a site where carbon dioxide can be concentrated around Rubisco to avoid photorespiration.
$C_4$ carbon fixation is a photosynthetic process of several plants, it is one of three known processes for fixation of carbon. It is involved in extracting carbon from carbon dioxide to be used in sugar and other biomolecules. The name is due to the occurrence of 4-carbon molecules as a first product of this carbon fixation. $C_4$ fixation is an elaboration of $C_3$ carbon fixation. It is believed to be evolution of $C_3$plants.

Thus, the correct option is- B. presence of bundle sheath.

Note: The bundle sheath prevents mixing of gases, keeps oxygen separated from Rubisco which is necessary to retain its functionality in the process of carbon fixation.