Selasa, 09 Oktober 2012

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Structure Of Plant Organ

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Structure Of Plant Organ. Organ is a composition of tissues doing particular function together. Main plant organs that have vegetative characteristic consist of root (radix). Stem (caulis), and leaf (folium). Other organs, such as flower and fruit, are derived from one/more main organs, or from a group of several main organs.


Root  
Root is  a plant organ that anchors into the soil. The function is to absorb water and mineral salts from the soil, strengthen the plant erection, store food, and as respiratory organ, e.g. mangrove root.
Root develops from meristem at the tip of the root that is covered by root cap (calyptra). Root cap is derived from apical meristem know as calyptroge and consist of parenchyma cells.

Apical meristem division forms maturation zone, elongation zone, and division cell zone. In elongation zone, root cell develop into permanent cell, namely xylem, phloem, parenchyma, and scerenchyma.

Coleorhiza in embryo or seedling grows into primary root. The growth of primary root due to cambium activities form secondary root.

Root can be distinguished into tree types, tap root on dicotyledon, fibrous root on monocotyledon, and adventitious root. Adventitious root is not derived from primary root. For Example, root of stem segment, and root of stem bulb.

In root anatomy, the orderly structure from outward to inward is epidermis, cortex, endodermis, and vascular cylinder.

Epidermis 
The epidermis of root consists of a single layer cell that is tighly packed without intercellular air space. The walls are thin and semipermeable. The presence of epidermal cell behind the growth point of root causes the root surface larger, therefore the substance absorption becomes more efficient.

The cell wall of epidermis that is far from the tips of root thickens and is impermeable. Epidermis cells of root can undergo modification by extending and protruding into the soil, which are known as root hairs.

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