Effects of Pb²⁺ and Cd²⁺ Stresses on Leaf Ultrastructure of Ficus parvifolia

In this study, the annual Ficus parvifolia seedlings were took as experimental materials.The effects of single and complex Pb²⁺ and Cd²⁺ stresses with different concentrations on leaf ultrastructure and chlorophyll content were studied.The results showed that leaf ultrastructure of F.parvifolia under Pb²⁺ stresses exhibited chloroplast with lower swelling and vacuolization degree, smaller change of starch grains and granules.Moreover, the content of chlorophyll showed an increasing tendency which suggested the seedlings had more tolerance to Pb²⁺ treatment.Under Cd²⁺ stresses, there were relatively heavy degree damages of leaves ultrastructure with the Cd²⁺ contents increasing.More specifically, the grana lamellae of the chloroplast structure arranged in disorder, broken and twisted.Besides, more starches and significantly decreasing chlorophyll content in the F.parvifolia leaves cell were observed.Under Pb²⁺+Cd²⁺ conbined stresses, mesophyll cell membrane was thinner.More loose and unintegrated of chloroplast structure, heavier disintegrated chloroplast structure, disappeared thylakoid structure, broken cell membrane and organelle structure were observed.Moreover, chlorophyll contents of F.parvifolia under Pb²⁺+Cd²⁺ combined stresses were lower than single stress treatment.In a word, the changes of chlorophyll contents, the leaf cell ultrastructure and the chloroplast ultrastructure indicated that the damaged degree of F.parvifolia seedlings was Pb²⁺+Cd²⁺ combined stress > Cd²⁺ stress> Pb²⁺ stress.