Question

A twig kept in water having some salt remains fresh for a longer period due to:
A. Decrease in bacterial degradation
B. Exosmosis
C. Decrease in transpiration rate
D. Absorption of more water

Answer 1

Hint: Concentration gradient between twig and outer environment decreases. The tendency of water to go from twig to the surrounding medium decreases. This results in reduced water loss from the plant.

Complete answer:
-A concentration gradient is always required for osmosis to take place.
 -Greater the concentration gradient is the tendency for fluid to move from the region of its higher concentration to lower concentration.
-Since the water contains salt, this gradient decreases.
- As a result, the transpiration rate is reduced.
- Usually, loss of water leads to wilting of the twig. However, in this case, water loss is reduced so there are fewer chances for wilting. Water is retained within the plant hence it remains fresh for a longer period.

So, the correct option is ‘Decrease in transpiration rate’.

Additional information:
-In transpiration, water is lost in the form of vapor from the mesophyll cells.
-Transpiration is very important to maintain the turgidity of cells and to maintain a cool surface on leaves.
-If transpiration is absent, plants will burst due to the presence of excess water.
-Mosses, liverworts, hornworts, and green algae do not transpire because of the lack of vascular systems.
-Temperature, humidity, movement of air are some of the factors that affect transpiration.
-Osmosis occurs at a high rate if the difference in solute concentration across the membrane is higher.
-It can be exosmosis as well as endosmosis.

Note: Osmosis finds its application in many areas. It assists plants in receiving water, preservation of fruit and meat, desalination of seawater, and even in kidney dialysis.
When water is lost by transpiration, negative pressure is created at the leaf surface. It is due to this gradient that water is moved upward from roots through the xylem.