Wilting refers to the loss of turgidity of leaves and other soft aerial parts of a plant causing droping, folding and rolling of non-woody plants. It occurs when rate of loss of water is higher than the rate of absorption.
| Temporary Wilting | Permanent Wilting |
|---|---|
| Temporary drooping of young leaves and shoots due to loss of turgidity especially during noon. | State of permanent loss of turgidity in leaves and other parts of plant. |
| Occurs when rate of transpiration is more than water absorption due to shrinkage of roots. | Rate of transpiration is more than rate of absorption but difference is below critical level. |
| Wilting recovers as soon as water is replenished in the soil around root hairs. | Wilting is not recovered as cells do not regain their turgidity even in presence of plentiful water and atmosphere. |
| Plant regains its normal growth. | Plant eventually dies. |
Which of these is a Semipermeable Membrane (SP) and which is Selectively Permeable (SL)?
(a) Animal bladder (b) Plasmalemma (c) Tonoplast (d) Parchment membrane (e) Egg membrane
Animal bladder Semipermeable
Plasmalemma Selectively permeable
Tonoplast Selectively permeable
Parchment membrane Semipermeable
Egg membrane Semipermeable
If a radio labelled carbon $C^{14}$ in is supplied to patato plants while it's carrying out photosynthesis in the presence of light, the $\mathrm{C}^{14} \mathrm{O}_2$ will be fixed and form radioactive products of photosynthesis, i.e., glucose $\mathrm{C}_6^{14} \mathrm{H}_{12} \mathrm{O}_6$.
This radioacative glucose is converted to sucrose which would again be radioactive due to transfer of $C^{14}$ from previous sugar molecule. These sucrose molecules then move into pholem and transported to other parts of plant.
Autoradiography technique detects the radioactive carbon (present in sugars) and traces the components and movement in the plant, i.e., through sieve tube channels of phloem from leaves (sources) to different parts (sink).
Attraction of water molecules to polar surfaces describes the adhesive properties of water. Besides, the cohesive properties include the attraction between water molecules. These two cohesive and adhesive properties contributes and help in the upward movement of water by providing.
| (i) High tensile strength | Capability to resist a pulling force, i.e., gravitational force. |
|---|---|
| (ii) High capilarity | Ability to rise in thin tubes or columns, i.e., of tracheids and vessels. |
The intermolecular hydrogen bonding in water ensures that more water molecules are attraction to each other in liquid state than in the gaseous state. This contributes to surface tension which in turn accounts for high capillarity in the xylem column.