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Shoot System of Plant Body (With Diagram)!
Given the requisite conditions, the seedling soon develops a luxuriant plant.
What one sees above is the shoot system or the ascending axis developed out of the plumule while below, covered by the soil, is an equally important portion—the root system.
The shoot is the emblem of greenness because of the green leaves while the root, growing in darkness, is never green.
The skeleton of the shoot is formed by the stem. The main stem is developed as a direct prolongation of the tigellum of the embryo and grows vertically up while its branches grow horizontally or may be somewhat inclined.
On the stem are borne the similar branch stems, the leafy appendages that are dissimilar to the stem and the reproductive modifications of shoot which are commonly called flowers. The young stem is green but later on it may change its appearance because of secondary growth and the formation of bark. A stem may bear multicellular hairs and branches on it develop exogenously.
As opposed to the root, the nodes divide the stem into internodes, the internodal Regions being bare while leaves and branches come out only from the nodal regions. If the nodes are very prominently developed, as in some grasses, the stem has a jointed or articulated appearance. A stem is usually cylindrical but it may be triangular (Cyperus rotundas), square (Labiatae), ribbed with ridges and furrows (Cucurbita), flat (Cactaceae), etc.
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It is usually solid but the pith may disorganise rendering it hollow or fistular as in many grasses. The surface of the stem may be smooth or glabrous, hairy, prickled or spiny, etc.
The normal stem supports its own branches and the leaves, which latter carry on the important physiological functions of photosynthesis and transpiration. By virtue of the chlorophyll and the stomata which are present in the young stem it can also carry on the functions of a leaf but to a limited extent.
Conduction of mineral solutions from the root to the leaves and of prepared food from the leaf to the different parts goes on through the xylem and the phloem, respectively, of the stem.
A shoot has its origin in a bud.
