Modification of parenchyma tissue to suit its functions.

Modification of parenchyma tissue to suit its functions.

• It forms irregular cells with storage granules and wide triangular intercellular spaces in the central pith of stems and outer cortex of stems and roots; here it functions as packaging and storage tissue.
• Due to presence of storage granules and intercellular spaces, they absorb water, become turgid and tightly packed and so provide support for the organs in which they form the main means of support.
• Parenchyma cells may have large air spaces and vacuoles to form parenchyma which is important in providing buoyancy to certain water plants.
• A system of air spaces runs from the external environment where they open as stoma (in leaves) or lenticel (in stems). These air spaces run between cells and allow gaseous exchange to take place between living cells and the external environment.
• Parenchyma cells may be flattened to form a one-cell thick layer that covers most parts of the plant as epidermis. This is usually covered with wax and helps to protect the plant from desiccation.
• Photosynthetic parenchyma, also called collenchyma, contains chlorophyll that traps light energy for the process of photosynthesis. It is usually found in the palisade layer of leaves exposed to sunlight.
• Companion cells are specialized parenchyma cells found adjacent to sieve tubes and are vital for the functioning of the latter. They are very active metabolically and how the denser cytoplasm, larger nucleus and smaller vacuoles than normal parenchyma cells denser exposed to sunlight.

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