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प्रश्न
What are the limitations of root pressure theory?
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उत्तर
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.
संबंधित प्रश्न
Describe the mechanism of opening and closing of stomata.
Answer the following question.
Explain the role of transpiration.
Why is transpiration is called ‘a necessary evil’?
What is transpiration?
Answer the following question.
What is the significance of transpiration?
Sketch and label - structure of stomata[ apparatus.
Sketch and label:
Types of guard cells
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 |
In plants, active absorption usually does NOT occur when ______.
Аccessory cells of stomata are reservoirs of ______.
