
Explain the cohesion tension theory.
Answer
494.7k+ views
Hint: The cohesion tension theory explains the ascent of sap through the Xylem tissues. The water and other nutrients are absorbed by the root and are transported to the leaves by the xylem. The water is transported by the process of osmosis.
Complete answer:
Ascent of sap is the translocation of water molecules from the root to the leaves. It is an upward movement.
Henry H. Dixon and John Jolly put forward the cohesion-tension mechanism of ascent of sap in 1894.
The ascent of sap occurs between the root which is the region of positive pressure and the shoot which is the region of negative pressure.
The upward movement of water is due to the strong force of attraction between the water molecules which cannot be broken easily. This is called force of cohesion. There exists a force of adhesion between the water and the walls of the xylem. These two forces together are responsible for the continuous movement of sap in the xylem vessel.
The upward force is generated by the transpirational pull which is generated through loss of water through stomata. This creates a pulling action called the transpirational pull. This force is strong enough to pull water against the gravity.
Note: The transport of water through the xylem vessels is termed as passive transport. The other forces responsible for the ascent of sap is the capillary action, root pressure and other passive forces that develop in the plants. Also certain environmental factors like sunlight, moisture is also responsible.
Complete answer:
Ascent of sap is the translocation of water molecules from the root to the leaves. It is an upward movement.
Henry H. Dixon and John Jolly put forward the cohesion-tension mechanism of ascent of sap in 1894.
The ascent of sap occurs between the root which is the region of positive pressure and the shoot which is the region of negative pressure.
The upward movement of water is due to the strong force of attraction between the water molecules which cannot be broken easily. This is called force of cohesion. There exists a force of adhesion between the water and the walls of the xylem. These two forces together are responsible for the continuous movement of sap in the xylem vessel.
The upward force is generated by the transpirational pull which is generated through loss of water through stomata. This creates a pulling action called the transpirational pull. This force is strong enough to pull water against the gravity.
Note: The transport of water through the xylem vessels is termed as passive transport. The other forces responsible for the ascent of sap is the capillary action, root pressure and other passive forces that develop in the plants. Also certain environmental factors like sunlight, moisture is also responsible.
Recently Updated Pages
Power set of empty set has exactly subset class 11 maths CBSE

Master Class 10 Computer Science: Engaging Questions & Answers for Success

Master Class 10 General Knowledge: Engaging Questions & Answers for Success

Master Class 9 General Knowledge: Engaging Questions & Answers for Success

Master Class 9 English: Engaging Questions & Answers for Success

Master Class 9 Maths: Engaging Questions & Answers for Success

Trending doubts
1 ton equals to A 100 kg B 1000 kg C 10 kg D 10000 class 11 physics CBSE

Difference Between Prokaryotic Cells and Eukaryotic Cells

One Metric ton is equal to kg A 10000 B 1000 C 100 class 11 physics CBSE

How much is 23 kg in pounds class 11 chemistry CBSE

1 Quintal is equal to a 110 kg b 10 kg c 100kg d 1000 class 11 physics CBSE

Whales are warmblooded animals which live in cold seas class 11 biology CBSE
