Anatomical Aspects of Juice Sacs of Satsuma Mandarin in Relation to Translocation

Abstract

Anatomical features of developing juice sac in citrus fruits, satsuma mandarin (Citrus unshiu Marc.), were studied by light and transmission electron microscopy, to seek an explanation for the translocation of solutes from the dorsal vascular elements in the albedo of the pericarp. The development of juice sacs commenced on the inner wall of the locules just before anthesis. The juice sac primordia developed primarily by anticlinal divisions in the epidermal cells of the endocarp and by anticlinal and periclinal divisions in the sub-dermal layers. Differentiation into stalk and sac body began when the juice sacs were about 0.7mm in length. As the juice sac elongated, cell division occurred in the epidermal cells of the stalk region with walls in the stalk-axis direction. Accumulation of soluble solids into the juice sacs occurred after they had attained full size. There was no evidence of vascular or tracheid tissue in the stalk of the juice sac. Plasmodesmata were abundant in the thin cell walls of the parenchyma cells of the juice sac stalk.