Ultrastructural Location Of Lanthanum In Intact Plant And Studies On Its Mechanisms To Effects Of Cell Physiology And Biochemistry

Locations of rare earth element La³⁺ in root and leaf cells of cucumber seedling were firstly determined with transmission election microscope. Secondly, the effects of La(3+)on cell physiology and biochemistry in cucumber seedling leaves were studied. Finally, scanning electron microscope and energy-dispersive X-ray analysis were used to study the effects of La³⁺on the tissular distributions of seven necessary elements in leaves of cucumber seedling and multitracer technique was used to investigate the effects of La³⁺on the uptake and distribution of four radionuclides in growing cucumber, so as to explore the physiological mechanisms of La³⁺ to effect of plant growth. The results obtained here were summarized as follows:1. La³⁺ pellet granules existed in membranes of cytoplasm, vacuole and mitochondria of root cells. It indicated that La³⁺ could be taken up in root cell through plasmatic membrane and located in membranes of different cell organelles.2. There were not obvious effects of La³⁺ on the contents of relative water, total membrane lipid and SOD activities in cucumber seedling leaves. At 0.002-0.2mmolL^-1 La³⁺ concentrations, contents of chlorophyll and carotenoid and enzyme (CAT and POD) activities increased, while at 2mmolL^-1, those decreased. Accumulations of free proline increased with the increasing of La³⁺ concentrtions. The contents of MDA and ABA in leaves decreased treated with low concentrations of La³⁺ (0.002-0.2mmolL^-1). La³⁺ also influenced the accumulation of putrescine, spermidine and spermines in leaves. There were similar change tendency in the levels of Put and Spm, while the levels of Spd were different. In addition, after different concentrations of La³⁺ treatments, a 41KDa polypeptide...