Question

Compare set I with set II and mark the incorrect pairs.

Set I	Set II
i. Xylem	bidirectional
ii. Phloem	unidirectional
iii. Turgidity	outward direction
iv. Wall pressure	inward direction

• A. i and ii
• B. iii and iv
• C. i, ii and iii
• D. i, ii and iv

Answer 1

The correct option is A i and ii

Conduction of water, minerals and food is done by the vascular tissues: xylem and phloem.

Water along with mineral salts are absorbed from the roots and move towards the aerial parts through the xylem, hence it is unidirectional.

Glucose produced by the photosynthetically active parts such as leaves, is converted to sucrose for translocation by phloem to different parts of the plant where it can be either utilized or stored. However, during seasonal changes when new leaves and shoots grow, this movement is reversed. The stored sugar is extracted from parts such as roots and mobilised to the new developing shoots. Sucrose can also be translocated upwards from the leaves for apical growth of stem, flowers or fruits. Hence the movement of food in phloem is bidirectional.

A plant cell is said to be turgid when it swells due to entry of water pushing the cell membrane against the cell wall. This pressure built up by the cytoplasm exerts an outward pressure on the cell wall. This outward pressure is called turgor pressure.

The cell wall exerts an equal but opposite i.e. inward, pressure on the cytoplasm in response to the turgor pressure. This is called wall pressure.