The Histochemical And Ultrastructural Study Of Anther Development In Rhododendron L

At present, the ultrustructural features of developing anthers of Rhododendron were studied using transmission electron microscope technique. The characteristics of distribution of nutriment during the anther development were also studied using cytochemical technique. The results as following:1The nutriment accumulation during the anther developmentAnthers of Rhododendron display some regular features of nutriment metabolism and accumulation in different parts during its development. many starches are accumulated in the anther during sporogenous cell stage. At microspore mother cell (MMC) stage, A few lipids appear in the MMCs, which have formed a evident callose wall, meanwhile, many starches are also accumulated in tapetal cells.After MMC meiosis, A few lipids appear in thetetrad microspores,and The starches increase in the tapetal cells.At early microspore stage, a few lipids appear in tapetal cells and microspores cells.At late microspore stage, tapetal cells begin to degenerate.At early bicellular pollen stage, the number of starches and lipids appear in the pollen grain,and many starches are accumulated in the endothecium cells.Many micromolecule lipids and starches are accumulated in the mature pollen, and in the endothecium cells many starches are still exist.2The characteristic of cytoplasmic changeDuring anther development of Rhododendron, some organelles display quantitative and structural changes.In the sporogenous cell stage,there are many mitochondrias and plastids, and the inner structure of mitochondrias and plastids are normal.There are alse some big vacuoles.At the microspore mother cell stage,mitochondrias and plastids decrease in number and the inner structure becomes indistinct.It begins to appear some small vacuoles in the cytoplasm.At the meiosis of the microspore mother cell, there are no mitochondrias and plastids, but it exists some vacuoles in the cytoplasm.At early microspore stage,there are many mitochondrias and plastids,but the vacuoles disappear.At the late microspore stage,. A big vacuole occupies most space of microspore, which creates a polarity of microspore, preparing for asymmetric gametophytic division,and there are a few mitochondrias and plastids at the around of cell nucleus.There are no mitochondrias and plastids in the mature pollen.3The development of the pollen wallAfter the meiosis of the microspore mother cell, it appeares discontinuous gap in the cytoplasm.The intine edge of the cell gap begin to accumulate sporopolleninprecursor substances. At the early microspore stage,microspores form thin primary wall.It exists some cytoplasmic channels at the primary wall,and then sporopollenin constantly gather at the primary wall.At the middle microspore stage,because of the connection of the exospore, the microspores combine together.This snap microspores is called compound pollen. At the late microspore stage,the lining material is accumulated at the between plasmalemma and extine.The pollen intine begin to develop.In the mature pollen,the structure of extine covering layer is tight,and the prismatic layer becomes indistinct.The pollen intine has become mature,and the pollen wall has formed.4The change of vacuoles in pollenDuring the pollen development of Rhododendron, the vacuolization takes place three times. The first time is from sporogenous cell stage to the microspore mother cells (MMC) stage,and there are some vacuoles in the cytoplasm.Then many vacuoles appear again to increase volume of cell and preparing for tetrad from MMCs meiosis stage to the microspore stage.The third time the vacuolization takes place at the late microspores. A big vacuole occupies most space of microspore, which creates a polarity of microspore,preparing for asymmetric gametophytic division.5The characteristic of tapetumThe tapetum of Rhododendronis glandular, and p-tapetum and c-tapetum have no differences from the volume and pattern. At the sporogenous cell stage, the tapetum cells and sporogenous cells have no differences from the volume and pattern,so the tapetum cells and sporogenous cells is the same origin which come from primary sporogenous cell.At the microspore mother cells (MMC) stage,the tapetum cells continue to develop,and the cytoplasm is thicker.There are many starches and vacuoles.At the middle microspore stage, it synthesizes Ubisch bodies at the surface of cell wall.At the late microspore stage, the tapetum cells begin to degenerate, but the number of Ubisch bodies is increasing. At the mature pollen stage, there are still a few Ubisch bodies in the tapetum wreckage.