Question

The transport system in plants consists of two kinds of tissues X and Y. The tissue X is made up of living cells and consists of two components A and B. The component A has tiny pores in its end walls and contains only cytoplasm but no nucleus. On the other hand, component B has cytoplasm as well as nucleus. The tissue Y is made up of dead cells and consists of two components C and D. The component C has open ends whereas component D does not have open ends. In flowering plants, either only C or both C and D transport water but D is the only water conducting tissue in non-flowering plants.
(a) What is (i) tissue X (ii) component A, and (iii) component B?
(b) What is (i) tissue Y (ii) component C, and (iii) component D?

Answer 1

(a)
(i) The tissue X is phloem. Phloem is made of living cells and helps in the transport of food from leaves to other parts of the body.
(ii) A sieve tube, which forms the phloem, has tiny pores in its end walls and contains only cytoplasm. It does not have any nucleus. Hence, component A is a sieve tube.
(iii) Companion cell is a component of phloem and has cytoplasm as well as nucleus. Hence, component B is a companion cell. 

(b)
(i) Tissue Y is xylem. It is made of dead cells and helps in the transport of water and minerals from the soil via roots to the rest of the plant body.
(ii) Xylem vessel is a component of xylem and has open ends. Hence, component C is xylem.
(iii) Tracheid does not have open ends. Hence, component D is a tracheid.