RESEARCH OF THE CONTRACTION PHASES ⅠAND Ⅱ OF MICROSPORE DEVELOPMENT IN RICE

It is well known that there are twice failings of microspore wall called first and second contraction phases individually in the rice microspore development. Some investigators think that these microspore contractions are artifacts caused by fixative irritating cells. Several methods with which microspore development is studied are described in this paper. They are:ultraathin section of TEM and specimen scan of SEM after double fixing with glutaraldehyde and osmium teroxide; paraffin section after fixing individually with glutaraldehyde and Caranoy's fixative; optical observation of the supravital stain. The results of comparision among these methods show that there are always first and second contraction phases. Having analysed many photographs, authors think that the first contraction phase is due to the decrease of water potential in loculus and the outflow of water of microspore caused by secretion of many forming-wall materials in tapetum. Then microspore restores gradually through metabolism growth, volume inflation, osmotic balance. The second contraction is due to the nurture pressure increased incessantly in loculus after intensive hydrolysis of cytoplasm, discruption of partial plasmic membranes and outflow of protoplasm, then turgot loss. The microspore restores untill its exine development increases hardness and equilibrium of inside and outside pressure is reached. Also authors think that apprearances of twice contractions are normal physiological processes in the micropore development of many plants, not artifacts caused by the fixative.