Effects of Cadmium Stress on Seed Germination and Seedling Growth of Cynanchum bungei Decne.
In order to investigate the tolerance of Cynanchum bungei Decne.to heavy metal cadmium and the action mechanism of cadmium on it,the seeds and seedlings of C.bungei were treated with cadmium chlo-ride at different concentrations(0,5,50,100,200,400,800 μmol/L).The effects of cadmium stress on seed germination,seedling growth and photosynthetic characteristics were studied.The results showed that with the increase of cadmium concentration,both the germination potential and germination rate of the seeds in-creased first and then decreased.Cadmium treatments had inhibitory effects on root and stem elongation of the germinated seedlings,and the higher the concentration of cadmium was,the more obvious the inhibitory effect was.Under soil culture conditions,cadmium could affect the growth of C.bungei seedlings,showing a trend of first promoting and then inhibiting with the increase of cadmium concentration,that was,low concentration of cadmium could increase the plant height and the number and biomass of leaves,while high concentration of cadmium could inhibit the growth of plants,decrease the biomass,and lead to thin,small and yellow leaves.When the cadmium concentration was between 100 and 400 μmol/L,there was no significant difference in chlorophyll content of the soil cultivated seedlings between cadmium treatments and the control,but the other cadmium treatments had larger or significant inhibitory effects on the increase of chlorophyll content.The pho-tosynthetic indicators of soil cultivated seedlings in the cadmium treatments increased first and then decreased with the increase of cadmium concentration.In conclusion,C.bungei had a certain tolerance to cadmium stress,and cadmium treatment could promote seed germination and seedling growth within a certain range of concentration;but when the cadmium concentration increased,it showed inhibitory effects on both seed germi-nation and seedling growth.
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