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.

1. What is (i) tissue X (ii) component A, and (iii) component B?
2. What is (i) tissue Y (ii) component C, and (iii) component D?

Answer 1

(a)

1. The tissue X is phloem. Phloem is made of living cells and helps transport food from leaves to other parts of the plant.
2. A sieve tube, which forms the phloem, has tiny pores in its end walls and contains only cytoplasm. It does not have a nucleus. Hence, component A is a sieve tube.
3. A companion cell is a component of phloem and contains cytoplasm and a nucleus. Hence, component B is a companion cell. 

(b)

1. Tissue Y is a xylem vessel element. 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.
2. A xylem vessel is a component of xylem and has open ends. Hence, component C is xylem.
3. Tracheid does not have open ends. Hence, component D is a tracheid.