STUDIES ON THE DEVELOPMENT AND ULTRASTRUCTURE OF THE GLANDULAR HAIRS IN BRASENIA SCHREBERI GMEL
Shi Guoxin Xu Xiangshen Wang Wen Du Kaihe (DePartment of Biology,Nanjing Normal University,Nanjing 210024)
Part of epidermal cells of the young laminae,leaf stalks and pedi- cels of Brasenia schreberi Gmel.develop into glandular hairs through se- veral successive transverse divisions.Each glandular hair consists of a basal cell,2—3 stalk cells and a head cell bearing the function of mucilage secretion at its full grown stage.The shape of head cell may be a vertical column or an elliptical one lying horizontally on the stalk cell,or even dichotomously branched depending upon whether the- re are obstructions around the head cell during its development. The constituents of the mucilage secreted by the head cell are pro- ved to be polysaccharides by the method of silver methenamine tech- nique.Ultrastructural observations reveal that mucilage is synthesized in the cisternae of Golgi apparatus and is eliminated from the protop- last.At the stage of active secretion,cisternae of Golgi apparatus di- late vigorously,and a large space of the head cell is occupied by such dilated cisternae arranged in a more or less regular order.Mucilage fil- led vesicles formed by such cisternae move toward the cell periphery where the vesicular membrane makes contact with plasmalemma of the head cell.The content of the vesicle is discharged through plasmalemma to the space between plasmalemma and wall layer.Microfibrils of the mucilage are deposited to the wall layer while the rest substance exudes out of the wall and be accumulated there.The cuticle outside the mu- cilage ruptures finally,leaving mucilage covers around the plant. The stalk cells contain numerous mitochondria,and are characte- rized by wall ingrowths.Colutes may be trasfered from parenchyma to head cells by these cells.