Question

Leaves of a healthy potted plant were coated with Vaseline for a long time. What will happen?
A) It will not get oxygen for respiration
B) It will not get carbon dioxide for photosynthesis
C) Upward movement of water and mineral would be hampered due to lack of transpiration
D) All of the above

Answer 1

Hint: A plant needs an adequate amount of water sunlight and carbon dioxide to survive. The upward movement of minerals and water is affected by Transpirational pull which itself depends upon the numbers of stomata.

Complete Answer:
- As the consequences of applying Vaseline (wax) on the leaf of a healthy potted plant, the stomatal pores of the leaves get cloaked which ultimately result in the negative impact on the survival of the plant.
- The plant leaves will not be able to get required oxygen for respiration also It will not be able to get carbon dioxide for photosynthesis and as transpiration get hampered the transpirational pull which is one of the major force used by plant for the upward movement of water and minerals from root to tip.

All the above points prove to be correct in relation to the Transpiration Pull and Cohesion theory
- Theory was proposed by Dixon and Jolly (1894). According to this theory leaves lose water into the atmosphere due to transpiration resulting in the decreased water potential of mesophyll cells. These cells draw water from adjacent cells having high water potential. This potential gradient extends upto sap of xylem.

Therefore the correct answer is D (i.e. all the above).

Note: Because of cohesive and adhesive forces, the water column does not break and is pulled upward by the force called as transpiration pull.
- Thus transpiration tension pulls water upwards by a force from roots and cohesive force maintains the continuity of the water column.