Advertisements
Advertisements
Question
What are the limitations of root pressure theory?
Solution
Although the ascent of sap takes place due to root pressure, there are certain objections raised, such as:
- It is not applicable to plants taller than 20 meters.
- Ascent of sap can also occur even in the absence of a root system.
- The root pressure value is almost nearly zero in taller gymnosperm trees.
- In actively transpiring plants, no root pressure is developed.
- Xylem sap under normal conditions is under tension, i.e., it shows negative hydrostatic pressure or high osmotic pressure.
Thus, root pressure is not the sole mechanism explaining the ascent of sap in all plants of varying heights.
RELATED QUESTIONS
What is dark reaction in photosynthesis?
Describe C3 Pathway.
Describe the mechanism of opening and closing of stomata.
Answer the following question.
Explain the role of transpiration.
Explain the root pressure theory.
Why is transpiration is called ‘a necessary evil’?
Which of the following term correctly describes the membrane which allows passage of certain substances more readily than others?
Guard cells differ from epidermal cells in having
Give an example of plant having both kidney and dumb-bell shaped guard cells in stomata.
Match the columns:
| Column A (Scientist) | Column B (Theory) | ||
| (1) | Dixon and Joylly | (a) | Starch-sugar inter-conversion theory |
| (2) | Steward | (b) | Osmotic absorption theory |
| (3) | Atkins and Pristley | (c) | Non-osmotic absorption theory |
| (4) | Kramer and Thimann | (d) | Cohesion tension theory |
