Studies On The SEs Ultrastucture Of Arabidopsis Thaliana L. And Triticum Aestivum L

The different development stages of root tips and the ultrastructure of the root SEs of Arabidopsis thaliana L. with different fixation methods and the effects of different fixing methods on ultrastructure of the SEs in monocotyledon plants were investigated using transmission electron microscope technique.The results show that during the differentiation of the SEs in the Arabidopsis thaliana L. the inclusions of the protoplasm are selectively degraded and the electron density decrease in the protoplasm results in the electron-translucent stroma gradually.In the cytoplasm of the completely mature SEs the mitochondria,plastids and ER are few in number. The deposits of P-protein occurred on the parietal wall.The sieve plate and sieve-pore completely formed lately. Changes of differentiation in the SEs of Arabidopsis thaliana L occur quite rapidly during the whole development of a SE.The root of Arabidopsis thaliana L fixed after incision was injured very seriously.The inclusions of the SEs dispersed and most deposited on the sieve plate.The P-protein dispersed into clots and accumulated near the sieve plate. The sieve-pore was occluded .Compared with the fixation of the Arabidopsis thaliana L after excision ,the in situ fixation of the whole plant body without excision was injured slighter.The structure of some membranous organelles still kept intactThe mitochondria still locate on the parietal wall,but the P-protein with dispersed appearance extend over the whole SE.The sieve-pore was occluded by P-protein.First prepared the whole body of Arabidopsis thaliana L with 1/2 MS liquid culture medium, then added the fixative liquid drop-by- drop. In the SE the inclusions including the P-protein arrange well in situ situ position and no appearce or location change. The Sieve-pore is unoccluded.The sieve tubes are functionally.The method can protect the SE well so that the ultrastructure of SEs is in intact state.Study on the sample fixed after keeping 3-4 days in the dark.The inclusions of the SEs and company cells degraded partly.The sieve-pore was unoccluded. So when there was a lack of supply inclusions,there was no accumulation of inclusions near the sive plate.And only few P-protein fibre will accumulate near the sieve plateThe Sieve-pore was unoccluded,so the inclusions of SEs probably take part role in the occlusion of the SEsFixation of root of the Arabidopsis thaliana L after preparation with chelator of Ca²⁺ ,EDTA, it can be seen that even the excision of the sample to injure the SEs seriously the compact p-protein was still dense and did not disperse. The sieve-pore was occluded by the compact P-protein.The study shows that Ca²⁺ acts as dispersing agent for P-protein.The study on the ultrastructure of the roots of wheat shows that fixation after recovery can keep theses in functional state .