Info

bundles

Oil cell frequency

Very high

Least

High

Less

Curcumin cell

None

Present

Present

None

Leaf Anatomical Features

Ginger leaves are isobilateral. The upper epidermal cells of leaf are polygonal and predominantly elongated at right angles to the long axis of the leaf. In the lower epidermis the cells are polygonal and irregular, except at the vein region, where they are vertically elongated and thick walled. The epidermal cells in the scale and sheath leaves (the first two to five leaves above the ground are without leaf blades) are elongated and parallel to the long axis of the leaf. Oil cells in the upper and lower epidermis are rectangular, thick walled, and suberized. Unicellular hairs are present in the lower epidermis of the foliage leaves. Occasionally, a hair is present at the polar side of the stomata.

Ginger leaves are amphistomatic. A distinct substomatal chamber is present. Stomata are either diperigenous or tetraperigenous. Occasionally, anisocytic stomata are also observed. The subsidiary cells are completely aligned longitudinally with the guard cell. The lateral subsidiary cells may divide to form anisocytic stomata. Occasionally, three to five lateral subsidiary cells are formed by further division (Raju and Shah, 1975).

The guard cells on the foliage leaves are 40.6 fxm long, whereas those on the sheath and scale leaves are 28.9 (xm long. The stomata on the scale leaves and rarely on the sheath leaves show pear-shaped guard cells with a large central pore. The nuclei of the guard cells are smaller than those in the subsidiary cells. Raju and Shah (1975) also reported the uncommon wall thickening at the polar ends of the guard cells. This wall thickening may be restricted to the outer wall at the polar regions or may also be extended to the common inner cell wall.

Tomlinson (1956) gave a brief note on the petiolar anatomy of ginger. The short petiole shows a swollen pulvinus-like appearance. A transection just above the pulvinus shows typical structure with two bundle arcs, air canals, and collenchyma. A transection through the pulvinus shows a different structure. Here air canals and assimilating tissue are absent, there is extensive hypertrophy of ground tissue parenchymal cells, and abundant deposition of tanniferous substances. The most striking feature according to Tomlinson (1956) is the collenchymatous thickening of the cells of the bundle sheath, Below the pulvinus the structure is again normal as that of the above pulvinus region.

Table 2.2 gives the comparative leaf anatomical features of four species of Zingiber. The stomata are tetracyclic in all the species. The first two subsidiary cells are parallel to the guard cells and the other two lie at right angles. In Z. officinale, Z. roseum, and Z. macrostachyum there is a special thickening in the upper and lower sides of the guard cell, but Z. zerumbet showed some extra thickening on the corners of subsidiary cells. The stomatal index was higher in Z. zerumbet. Guard cells were the largest in Z. zerumbet, followed by Z. officinale and Z. macrostachyum. In Z. roseum the guard cells were shorter and broader.

Stomatal ontogeny: Raju and Shah (1975) described the structure and ontogeny of stomata of ginger. Here the differentiation of a guard cell mother cell or a meristemoid occurs by an asymmetrical division of protodermal cells. The meristemoid is distinguished from the adjacent protodermal cells by its small size, dense stainability of cytoplasm, and less vacuolation. The anticlinal wall of the meristemoid appears lightly stained with periodic acid—Schiff (PAS) reaction than the lateral walls of the epidermal cell and the meriste-moid. The epidermal cell on either side of the meristemoid divides to form a small subsidiary cell. This epidermal cell shows dense stainability for nuclear DNA. The young lateral subsidiary cells are smaller than other epidermal cells. Later the meristemoid

Table 2.2 Leaf anatomical characteristics in four species of ginger

Tissues

Z. officinale

Z. macrostachyum

Z. zerumbet

Z. roseum

Epidermis

Upper larger than

Both epidermis

Both epidermis

Both epidermis

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