Question

Kranz anatomy is found in the leaves of
A) \[{{C}_{3}}\] Plants
B) \[{{C}_{4}}\] plants
C) Both \[{{C}_{3}}\] and \[{{C}_{4}}\] plants
D) None of the above

Answer 1

Hint:The key differences between the \[{{C}_{3}}\] and\[{{C}_{4}}\]
plants are that the\[{{C}_{3}}\] plants 'bundle sheath cells do not contain chloroplast, whereas the \[{{C}_{4}}\]plants' bundle sheath cells do. In\[{{C}_{3}}\] plants, carbon dioxide fixation takes place only once, while in\[{{C}_{4}}\] plants, fixation takes place twice. The term Kranz refers to "wreath" or "ring."

Complete answer:
Kranz anatomy is a specialised structure around the bundle-sheath cells in plants where the mesophyll cells are clustered in a ring-like fashion. The number of chloroplasts in the bundle-sheath cells is more than the number in the mesophyll cells.
In \[{{C}_{4}}\] grasses, such as maize and a few dicots, this is found. In three separate steps, the Kranz anatomy is developed:
-Procambium initiation
-Bundle sheath and the specification of mesophyll cells
-Development of Chloroplast and integration of the\[{{C}_{4}}\] cycle

In the \[{{C}_{4}}\] plants, the light-dependent responses and the Calvin cycle are segregated. In the bundle-sheath cells, the Calvin cycle happens and the mesophyll cells have light-dependent reactions.
Atmospheric oxygen is first fixed in the mesophyll cells to form the 4-carbon compound oxaloacetate, catalysed by PEP carboxylase.

Oxaloacetate is transformed into malate that is carried to the bundle-sheath cells.Malate dissociates into free carbon dioxide in the bundle-sheath cells.Carbon dioxide is fixed by Rubisco and converted into sugars.

The mesophyll cells continuously pump carbon dioxide into the bundle sheath cells and the concentration of carbon dioxide around Rubisco is often higher. Photorespiration decreases this.

In the majority of plants, through the action of Ribulose bisphosphate carboxylase oxygenase (Rubisco), carbon dioxide is fixed into a 3 carbon compound. Rubisco may also catalyse an oxygen reaction that provides a wasteful mechanism called photorespiration. The\[{{C}_{4}}\] pathway fixes ambient carbon dioxide using the phosphoenolpyruvate carboxylase enzyme in order to solve this. Carbon dioxide is then released by Rubisco for refixation.

The mesophyll cells surround the bundle sheath cells in \[{{C}_{4}}\] grasses, such as maize, and the bundle sheath cells surround the veins.\[{{C}_{3}}\] plants do not have the morphology of Kranz. The bundle sheath cells do contain chloroplast in these plants and fixation of carbon dioxide occurs only once.

Thus the correct answer is option (B) \[{{C}_{4}}\] plants.

Note:Mesophyll cells:-
-There are several well-developed and large grana species.
-Carboxylase RuBP is absent. A \[{{C}_{3}}\] loop does not exist.
-High Photosystem II Operation.
-There were no starch grains present.
-Main starch synthesis enzymes are absent.