November 5, 2015

Senior Inter Botany - 2 Marks Questions from Plant Physiology

Q: Compare imbibing capacity of Pea seeds and Wheat seeds.
A: Pea seeds store proteins in its cotyledons. Wheat seeds store starch in the endosperm. The imbibing capacity of proteins is very high when compared to the starch (carbohydrates).

Q: In general in a plant which path of water movement is more and why?
A: There are 2 kinds of distinct pathways of water movement in the plants.
1) Apoplast Pathway
2) Symplast Pathway
Apoplastic movement of water occurs through the cell walls and intercellular places. It does not involves any crossing the cell membranes. Whereas symplast pathway occurs through the cytoplasm, plasmamembrane and
plasmodesmata. Hence Apoplast path of water movement in the plants is faster.

Q: Which structures do you think the Pinus plant does not possess due to which its seeds fail to germinate?
A: Pinus plant does not possess root hairs. So it can not absorb water on its own.

Q: What do you think is the driving force for ascent of sap?
A: Transpiration pull is the driving force ascent of sap.

Q: Why do stomata close under water stress conditions?
A: When there is insufficient water in the soil, plants are subjected to water stress. Then Abscisic Acid (ABA) is produced more and it induces the stomatal closure.

Q: How are stomata distributed in a typical monocot plant?
A: A typical monocot leaf has stomata on upper and lower epidermis. Such leaf is said to be Amphistomatic. The number of stomata is same on either side. So it can also be called isobilateral leaf.

Q: In what form the sugars are transported through Phloem?
A: Sugars are transported through Phloem in the form of sucrose.

Q: The inward movement of water into a plant begins either as symplast or apoplast. How does it conclude before entering into xylem?
A: The movement of water through the root layers from epidermis to cortex (endodermis) may be apoplastic or symplastic. But ultimately it is symplastic in the endodermis and pericycle, before entering into xylem.

Q: Why does the root endodermis transports ions in one direction only?
A: As mineral ions are dissolved in water the root endodermis transports ions in one direction only.

Q: Pressure potential in plant systems can be negative. Elaborate.
A: Pressure potential in plant systems can be some times negative - when the plants loose water by transpiration inspite of insufficient water in the soil.

Q: How does ABA bring about the closure of stomata under water stress conditions?
A: Under water stress conditions ABA (natural antitranspirant) closes the stomata by
1) changing the permeability of plasma membrane
2) driving out K+ ions out of guard cells.

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