Leaf Cell Damage and Change of Photosynthetic Pigment Contents Induced by Lead Stress in Three Species of Mosses

The damage of leaf cell,contents of photosynthetic pigments,and Pb2+ accumulations in three species of mosses(Dolichomitriopsis diversiformis,Plagiomnium acutum and Brachythecium procumbens) were studied by water culture experiments to investigate its responsiveness and tolerance to Pb2+ stress.The results showed that the lowest concentration of Pb2+ caused significant damage of leaf cell in D.diversiformis,P.acutum and B.procumbens is 100,1 and 10 mg·L-1,respectively,and the damage aggravated significantly with the increase of Pb2+ concentration;the order of tolerance to high concentration of Pb2+ was D.diversiformisP.acutumB.procumbens.Pb2+ stress at concentration less than 100 mg·L-1 had no effects on their total chlorophyll contents,whereas,Pb2+ stress at concentration of 100 and higher led to a significant decrease of total chlorophyll contents as evidenced by the order of B.procumbensP.acutumD.diversiformis.The change of chlorophyll a/b distinctly indicated that the inhibition of Pb2+ stress at high concentration on chlorophyll b in D.diversiformis was far greater than that on chlorophyll a.In P.acutum and B.procumbens,the inhibition on chlorophyll a was greater than that on chlorophyll b.Pb2+ concentration of 200 mg·L-1 caused significant decline of carotenoid contents.Three species mosses could significantly accumulate Pb2+,at high Pb2+ concentration,the accumulation to Pb2+ increased sharply,and the accumulation levels of Pb2+ in three mosses were positively correlated to their corresponding tolerance to Pb2+ stress.