28
How does most of the water moves within the root?
Explanation
Most of the water flow in the root occur via the apoplast pathway since, the cortical cells are loosly packed and hence offer no resistance to water movement, which is through mass flow. This mass flow of water occurs due to adhesive and cohesive properties of water.
However, symplast pathway is also involved in the movement of water molecules within the root (i.e., via endodermis to xylem).
29
Give the location of casparian strip and explain its role in the water movement.
Explanation
Casparian strip is found in the endodermis. The walls of this layer are impervious to water because of the presence of suberin. So, it does not allow movement of water across the endodermis, rather is forced to enter the symplast pathway through cell membranes and reaches the xylem.
30
Differentiate between guttation and transpiration.
Explanation
Difference between guttation and transpiration is as follows
Guttation | Transpiration |
---|---|
Guttation is the loss of liquid droplets from the plants. | It is the loss of water by a plant in the form of vapours. |
Guttated water is a dilute solution of both inorganic and organic substances. | Transpired water is a pure water. |
Guttation occurs at the margins and the tips of the leaves. | Transpiration occurs through the general surface of the leaves and the young stem. |
Excessive guttation does not cause loss of turgidity. | Excessive transpiration results in wilting in severe cases, could be lethal to plant. |
31
Transpiration is a necessary evil in plants. Explain
Explanation
The plant continuously lose water in the vapour form from its body surfaces. It creates a transpiration pull to absorb more and more water from soil through roots.
If the plant does not get water in soil, even then loss through transpiration is not stopped, so plant shows wilting sometimes it leads to the physiological wilting (non-recoverable) and plant dies. So, the transpiration is necessary evil.
32
Describe briefly the three physical properties of water which helps in ascent of water in xylem.
Explanation
The three physical properties of water that helps in ascent up to xylem are as given
Cohesive properties | Mutal attraction between molecules |
---|---|
Adhesive properties | Attraction of water molecules to polar surfaces (of tracheids) |
Surface tension | Water molecules get attracted to each other more in liquid phase than in gas phase. |