Question

The movement of water and dissolved minerals from the roots to the leaves is best explained by

• A. Cohesion-tension theory
• B. Translocation
• C. Tensile strength
• D. Pressure-flow hypothesis

Answer 1

The correct option is A Cohesion-tension theory

Despite the absence of a heart or circulatory system in plants, the flow of water upward through the xylem in plants can achieve fairly high rates upto 15 metres per hour. Most researchers believe that water is mainly “pulled through the plant and the driving force for this process is transpiration from the leaves. The movement of water and dissolved minerals from the roots to the leaves is best explained by Cohesion-tension theory. This theory was put forward by Dixon and Joly in 1894. This theory tells that there is a continuous column of water from root through the stem and into the leaves. Water molecules remain attached to one another by a strong mutual force of attraction called cohesion force. When water molecules are attracted to one another more than the water molecules in the gaseous state, it is called surface tension. When the tension develops due to transpiration, it is called transpirational pull

So, the correct answer is 'Cohesion-tension theory'