A: Though excessive transpiration retards growth of the plant and plants show permanent wilting, transpiration is beneficial to plants in many ways like
1) It helps in passive absorption of minerals and water.
2) It provides necessary force to pull the water during ascent of sap.
3) It regulates the temperature of the plant body.
4) It gives cooling effect.
Hence transpiration is a necessary evil.
Q: A gardener forgot to water a potted plant for a day in summer. What will happen to the plant? Do you think it is reversible? Explain.
A: The plant shows wilting. It is reversible. If the plant is again watered, it becomes normal. That wilting showed by the plant is temporary. If the plant is not watered, it becomes wilted permanent.
Q: Explain the type of molecular movement which is highly selective and requires special membrane proteins, but does not require any metabolic energy.
A: Hydrophilic substances or molecules are transported through the membrane proteins called Porins. The movement is highly selective. Porins are specific, special proteins present in the membrane which help in the facilitated transport without the expenditure of energy. It may be uniport, symport or antiport. It may be shown as follows.
1) Molecules move through the carrier independently in one direction. Ex: H+
2) Two molecules move in opposite direction.
Ex: Inward movement of H+ Outward movement of Na+
3) Two molecules move in the same direction. Ex: 1) H+, NO3 − 2) H+, Cl − 3) H+, PO4−
Q: How does most of the water move within a healthy plant body and by which path?
A: Water moves within a healthy plant body takes place through Xylem by apoplast pathway.
Q: Transpiration and Photosynthesis, a compromise. Explain.
A: Surface of the lamina is related to the rate of transpiration and photosynthesis.
1) If the lamina is large the rate of transpiration is more. If transpiration is more it may cause insufficient supply of water which further affects photosynthesis.
2) Lamina is reduced to reduce the rate of transpiration. In such case, rate of photosynthesis will also reduce as the lamina is narrow. Thus, plant has to survive by making a compromise between transpiration and photosynthesis.
Q: Do different species of plants growing in the same area show the same rate of transpiration at a particular time. Justify your comment.
A: The same area may be inhabited by different species belonging to mesophytes, xerophytes, dicots and monocots. If there is a pond, hydrophytes also grow there. Though they grow in the same area the rate of transpiration is not same because
1) Mesophytes- The rate of transpiration is more
2) Xerophytes- The rate of transpiration or amount of transpiration is less.
3) Hydrophytes show very less or no transpiration.
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