Effects Of Lead And/or Cadmium Pollution On The Growth And Development Of Four Mosses

As a very sensitive indicator to pollution, moss has been widely used to monitor heavy metal pollution. In this paper, we studied the toxic effects of Pb²⁺ , Cd²⁺and their combined pollution on Hypum hamulosum,Thuidium cymbifolium,Funaria hygrometrica and Haplocladium microphyllum by means of simulated test, measurement of physiological index, culture of unicell spore, observation of microstructure. The experimental results showed: (1) Different stress concentrations of Pb2+ and Cd²⁺ led to different poisoning symptoms to Hypum hamulosum and Thuidium cymbifolium. And the injury on external morphology has a positive correlation with culture concentration and time. With the increase of stress concentration and stress time, the poisoning symptoms became more and more serious. Mainly symptom was losing green, some mosses materials even died in high stress concentration at last. Comparing with Hypum hamulosum, Thuidium cymbifolium was more sensitive to lead and cadmium. (2)Under the stresses of Pb2+ and Cd²⁺, a series of change occurred in the substance and protective enzymes related with the adversity, and all indexes demonstrated a correlation between the does and effect: the higher the pollution concentration and the longer the pollution time are, the more serious the damage is. Soluble protein content and proline content increased first and deceased afterwards with enhancing treatment concentration and time. While malondialdehyde(MDA) content increased during the course. Under low concentration stress and short time treatment, the protective systems reacted on mosses, and the activities of superoxide dismutase(SOD) and peroxidase(POD) were induced in high level to eliminate and resolve ractive oxygen species(ROS) in order to maintain stability of membrane systems.With more serious damage, the defensive system of cells could not protect cells, MDA content increased evidently. Corresponding to injure symptom, the change of physiological index of Thuidium cymbifolium was more evident than Hypum hamulosum. Experimental results indicated that toxicity of Cd²⁺on mosses is heavier than that of Pb²⁺ under the same treating time and concentration., and the effects of combined pollution are stronger than those of single pollution . (3)The pattern of spore germination and protonemata development of Funaria hygrometrica is funaria-type, and the pattern of Haplocladium microphyllum is bryum-type. Under the optimal cultivation condition, the spores of Funaria hygrometrica germinated after 2～3 days and the rate of germination is over 90%. The early stage of protonemal system development has four types. About 15 days later bud premordium began to divide into buds. Around 43th day, gametophyte formed. The spore germination of Haplocladium microphyllum began 2³ days after inoculation,and the rate of germination is over 85%. About 10 days later, its chloronemata and caulonemata began to differentiate, but no rhizoids formed. Almost on the 30th day bud premordium appeared, and then buds formed gradually. Nearly the 60th day, gametophyte formed. After being treated with Pb2+, the germination percentage of the two mosses decreased. Protonematas formed later and were less numerous and shorter than control .Both the shape and size of the cells were altered. The protonemal system differentiated indistinctly, and abnormal branches and outgrowths were observed. The division of buds was influenced. The shape, size and distribution of the chloroplast were all abnormal.