Question

Theory of ‘Ascent of Sap’ was given by Dixon and Jolly. Which of them is against the theory?
A. Cohesive and adhesive properties of ${{H}_{2}}O$
B. Requirement of ATP
C. Presence of pores in the tracheary elements
D. All of the above

Answer 1

Ascent of sap theory is formed on transpirational pull of an uninterrupted water column in the xylem of plants. This pull is created due to loss of water through transpiration and does not require any kind of input energy.

Complete step by step answer:
Let’s discuss the options and find out the correct answer.
- In water, the property due to which positive and negative charges of the hydrogen and oxygen molecules respectively are attracted towards each other is called cohesive property of water. The adhesive property of water helps it to stick to other non-water molecules. In plants, adhesion helps water to move up against gravity through plant cells. These properties contribute to the ascent of sap theory.
- Ascent of sap theory is based on transpirational pull of an uninterrupted water column in the xylem of plants. This column is developed due to adhesion and cohesion forces. The transpirational pull is created passively due to loss of water and that does not require any sort of energy. So, ATP is not required in this theory.
- The dead, hollow cells with patterned cell walls consisting of xylem vessels and tracheid are known as tracheary elements. They act as conductive hollow tubs for water and nutrient transport throughout the body of the plant. This property is under the ascent of sap theory.
Hence, option B: Requirement of ATP is correct.

Note: Theory of ascent of sap was formed on three important hypotheses which are cohesion between water molecules, continuation of water column and transpirational pull.