Effects Of Ca～(2+) On The Cd～(2+) Toxicity-Resistance Of Alternanther Philoxeroider And Isolation And Purification Of Cd～(2+)-binding Protein

Nutrient solution culture experiment was conducted to study the effects of different concentration of Cd2+ and after additon Ca2+ (lOmmol.L-1) on the Cd's accumlation physiology and ultrastructure in vegetative organs of Alternanther philoxeroider through measurements of physiological indexes, analysis of atom absorption, observations of electron microscopy, electrophoresis and chromatography. The results showed that Cd2+ might injure photosynthetic systems, reactive oxygen species (ROS) scavenging system, and cell structure of macrophytes. Photosynthetic systems of Alternanther philoxeroider were injured deeply more and more by Cd2+ concentration from 0-10mg.L-1 and time from 0-20 day. When Ca2+ was added into the solution some photosynthetic systems could be reconstructed or toxicity be reduced , such as chlorophyll contents increased and photosynthetic rate and respiratory rate enhanced. Ca2+ decreased ROS content including 0-2 and H2O2 while the activities of superoxide dismutase (SOD), catalase (CAT), GSH-Px increased, so did the content of GSH. When compared with single Cd2+ treatment, Ca2+ could decrease or remove the toxic action of Cd2+ on Alternanther philoxeroider treated with different combination of Cd2+ and Ca2+, increase -SH content, stabilize membrane systems, decrease malondialdehyde (MDA) content. Ultrastructural observation indicated organellas had different tolerance: mitochondron >chloroplast> nucleus. Ca2+ had ability of reconstructing above three organellas, especially for nucleus. In order to study the tolerant mechanism, heavy metal-binding protein was purified. We measured the quantity of Cd2+ in different organs of Alternanther philoxeroider when Ca2+ was added .The result suggested Ca2+ could inhibit absorption of Cd2+ , amplify and accelerate the inducement of Cd2+- binding protein. PAGE and SDS-PAGE showed that its molecular weight was about 35.2KD. This protein had two subunits whose molecular weight were 18.8 KD and 16.0 KD respectively. Ca2+ could enhance production of this protein, As a inexpensive adjusted medication, according to the antagonism of Ca2+ to Cd2+, we can utilize and regenerate water resource that was polluted by Cd2+ or other heavy metals, so the double effects of protect the plant and environment could be attained.