Question

Where do the casparian bands occur

(a) epidermis

(b) endodermis

(c) pericycle

(d) phloem.

Answer 1

answer-b) The casparian strips are present in the endodermis layer of the plants. It is composed of the suberin and lignin molecules which are deposited on the walls of the endodermis. They are distributed in the form of rings. The movements of the salt ions and water is regulated through through the walls of endodermis containing the casparian strips.Suberin and lignin are polymers of the carbohydrate molecules. The effect of the environmental factors like heavy metal stress, alkalinity, temperature changes ,changes in the concentrations of the salt ions and their mobility across the tissue layers of the plant cell and the vascular bundles. The nutrients, metabolites, and salt ions move across the semi-permeable membrane of the cell wall of the plant tissues so that the nutrients can reach the vascular bundles containing xylem and phloem. Hence, option (b) is correct.

Epidermis is the outer layer of the plant cells. The water, ions,metabolites enter through this layer and reach the inner cells to transport the ions and the nutrients for the growth,differentiation and the development of the plant. capsarian strips are not present in the epidermis. Hence, option (a) is incorrect.

Pericycle is the inner layer of the plant tissues.It surrounds the vascular bundles of the plants containing the xylem and phloem vessels, tracheids and fibers for providing the nutrition for the growth of the plant and division of the cells. It does not contain the casparian strips. Hence, option (c) is incorrect.

Phloem tubes are present in the vascular bundles. It provides the food metabolites like sugars essential for the growth and differentiation of the plant. It does not contain the casparian strips.Hence, option (d) is incorrect.