Morphological aspects of the shedding of surface layers from peanut roots

Abstract

Epidermal cells and cells originating in the outer cortex form the surface layers of peanut (Arachis hypogaea) roots, the outermost of which separate and shed from the periphery. Shedding takes place continuously and over the whole surface of the root. Light and electron microscopic studies revealed that the shedding of surface layers involves modification of cell walls and separation of intact cells. Wall breakdown, as well as the expansion of cells resulting from wall breakdown, might facilitate the separation of intact cells. Examination of enzymes revealed that cellulase showed much higher activity in the shedding layers than in the remaining tissues. The results suggest that the cell separation process in peanut roots involves a wall-degrading enzyme-mediated mechanism. Key words: Arachis hypogaea, morphology, root, shedding, surface layers, wall breakdown.