Transpirational pull is responsible for the ascent of water in the xylem. This ascent of water is dependent on the following physical factors:
• Cohesion – Mutual attraction between water molecules
• Surface tension – Responsible for the greater attraction between water molecules in liquid phase than in gaseous phase
• Adhesion – Attraction of water molecules to polar surfaces
• Capillarity –Ability of water to rise in thin tubes.
These physical properties of water allow it to move against gravity in the xylem.
Which of the following is not correct?
(a) Robert Brown discovered the cell.
(b) Schleiden and Schwann formulated the cell theory.
(c) Virchow explained that cells are formed from pre-existing cells.
(d) A unicellular organism carries out its life activities within a single cell.
Answer briefly:
(a) Why are villi present in the intestine and not in the stomach?
(b) How does pepsinogen change into its active form?
(c) What are the basic layers of the wall of alimentary canal?
(d) How does bile help in the digestion of fats?
Distinguish between
(a) IRV and ERV
(b) Inspiratory capacity and Expiratory capacity
(c) Vital capacity and Total lung capacity
What is meant by double circulation? What is its significance?
Goodð
Not only transpiration pull is necessary others are also there
Not only transpiration pull is necessary others are also there
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