Plant Physiology

Step 1: Understanding the Concept:
Plants need to exchange gases with the atmosphere for photosynthesis and respiration, and regulate water loss.

Step 2: Detailed Explanation:
Definition: Stomata (singular: stoma) are microscopic pores or openings situated primarily in the epidermis of leaves (especially on the underside) and young stems. Each pore is flanked by two specialized guard cells that regulate its opening and closing.
Function:
1. Gas Exchange: They allow the intake of carbon dioxide (for photosynthesis) and the release of oxygen (a byproduct of photosynthesis) and carbon dioxide (from respiration).
2. Transpiration: They are the primary site for the evaporative loss of water vapor from the plant, which creates a transpirational pull helping in the ascent of sap.

Step 3: Final Answer:
Stomata are pores on leaves responsible for transpiration and the exchange of O and CO .

Step 1: Understanding the Concept:
Pollination is a crucial step in the sexual reproduction of flowering plants (angiosperms) and gymnosperms.

Step 2: Detailed Explanation:
It is defined as the physical transfer of pollen grains, which contain the male gametes, from the male reproductive organ (anther) to the receptive surface of the female reproductive organ (stigma).
This process can occur within the same flower (self-pollination) or between different flowers (cross-pollination) through agents like wind, water, or insects.

Step 3: Final Answer:
Pollination is the transfer of pollen grains from the anther to the stigma.

Step 1: Understanding the Concept:
Plant tissues responsible for the transport of materials are called vascular tissues.
There are two primary types of vascular tissues in higher plants: xylem and phloem.

Step 2: Detailed Explanation:
The xylem primarily conducts water and dissolved minerals from the roots upward to the stems and leaves of the plant.
The phloem, on the other hand, is responsible for the translocation of prepared food (like sucrose and amino acids) from the leaves to other parts of the plant.
Therefore, the function specifically assigned to the xylem is the transport of water.

Step 3: Final Answer:
The correct option is (D).