Some aspects of organization and histochemistry of the embryo sac ofScilla sibirica sato

Summary The present investigation deals with some of the organizational and histochemical aspects of the embryo sac ofScilla sibirica. Both the synergids and egg cell are invested by PAS-positive complete walls. The filiform apparatus comprises an elaborate system of fibrillar projections, showing extensive ramifications. The micropylar region of the embryo sac wall from where the filiform apparatus originates is composed of three distinct layers. On a histochemical basis it may be surmised that, unlike the egg cell, the synergids are metabolically very active. Two kinds of wall ingrowths (i) massive and highly branched very much akin to the filiform apparatus, and (ii) small tuberculate wall projections, are unique to the antipodal cells of S.sibirica. Small tuberculate projections have also been observed along the wall of the central cell adjacent to the nutrient-rich nucellar cells. The antipodals and the central cell show the presence of starch grains and abundant total proteins. All the cell types in the embryo sac ofS. sibirica are structurally so organized as to meet the requirements of its nutrition during pre- and postfertilization development. The presence of abundant PAS-positive granular substance in the cells of nucellar epidermis probably establishes a gradient which assists in the pollen tube growth.