Question

In $C_4$ plants, agranal Chloroplast are found in?
A) Mesophyll cells
B) Skin cell chloroplast of green stem
C) Bundle sheath cells
D) Chloroplast of guard cells

Answer 1

Hint: Chloroplast during a plant cell can be defined as a kind of plastid which exists as a double membrane-bound cell organelle that produces energy through photosynthesis. Agranal quiet chloroplast lacks grana and only contains stroma and stroma lamellae within the inner layer.

Complete answer:
In $C_4$ plants, Calvin cycle enzymes are present in chloroplasts of bundle sheath cells.In C4 plants, chloroplasts of mesophyll cells are smaller, grana rich and don't produce starch but chloroplasts of bundle sheath cells are larger and lack grana. In $C_4$ plants the bundle sheath cells contain chloroplasts and are the location of the Calvin cycle.

The initial fixation of $CO_2$ to make malic acid takes place within the palisade mesophyll cells, which in $C_4$ plants form a revolve around the bundle sheath. During a few $C_4$ species, the functional bundle sheath can exist independently of the vasculature.

These ‘distinctive’ cells appear as bundle sheath (Kranz)-like cells lying within the mesophyll, break away the parenchyma sheath, as single cells or in small groups (Johnson and Brown, 1973; Hattersley, 1984; Dengler et al., 1996).

These only occur during a few small panicoid tribes, which also are unusual in having widely spaced longitudinal veins, in striking contrast to other $C_4$ grasses during which close vein spacing may be a consistent feature (Dengler et al., 1996).

Hence, the correct answer is option ‘C’.

Note: Many $C_3$ plants have chlorenchyma tous bundle sheaths. The parenchyma sheath cells of so grasses contain chloroplasts, while the cells of other grasses don't (Rhoades and Carvalho, 1944). Similarly, leaves of some plants possess a bundle sheath which extends laterally beneath the palisade mesophyll cells, independently of the vasculature