Seed Epidermis Development and Histochemistry in Solanum melongenaL. and S. violaceumOrt.

Abstract

Structure, development and histochemistry of the seed epidermis were studied in Solanum melongenaL. and S. violaceumOrt. using light and scanning electron microscopy. The epidermal cells at the endosperm mother cell stage of ovule development had thickened outer periclinal walls, consisting of two layers, a thin inner layer, and a thick outer layer. The latter which stained positively for pectic substances became further thickened during the course of seed development; more so in S. melongena. The inner layer of the outer periclinal wall also was thickened by depositions of cellulose but remained comparatively thin. The development of the inner periclinal and anticlinal walls took place by the uneven deposition of concentric layers. These secondary wall thickenings which appeared as pyramids in transverse section stained for cellulose, lignin and pectin. Further uneven secondary thickenings near the outer part of the anticlinal walls resulted in the formation of projections which were hair- or ribbon-like in appearance. In S. melongena, these projections progressed only a short distance from the anticlinal wall. In S. violaceum, on the other hand, they grew much longer forming striations on the inside of the outer periclinal wall. In S. melongena, partial removal of the outer periclinal wall by enzyme etching exposed to surface view a beaded appearance of the cell boundaries. Complete erosion of the outer periclinal wall revealed the hair-like projections of the underlying anticlinal walls. In S. violaceum, enzyme treatment exposed the striations which formed bridge-like structures over the curves in the anticlinal walls.