Effect Of Cd²⁺?Pb²⁺ On Development And Rhizosphere Soil Microecology Of Three Species Of Chingese Cyatheaceae

Cyatheaceae is the only relict tree ferns since Jurassic Period,which has been endangered by habitat fragmentation.The community of Cyatheaceae has been restored with the increase of conservation intensity,but recent studies have found that most Cyatheaceae communities are experiencing decline and seedling reduction,some scholars also believe that the appearance of this phenomenon may be related to human activities.Cd²⁺,Pb²⁺are widely distributed heavy metal pollutants,with the development of mining industry and the use of fossil fuels,their pollution situation is becoming more and more serious.However,the effects of Cd²⁺,Pb²⁺stress on gametophytes and seedlings of Cyatheaceae plants have not been reported.Therefore,Sphaeropteris lepifera,Alsophila costularis and Alsophila gigantea were selected as materials in this study.Artificial simulation of Cd²⁺?0.2?0.4?0.8?1.6mg·kg^-11 for gametophytes,2?4?8?16mg·kg^-11 for seedlings?,Pb²⁺?20?40?80?160mg·kg^-11 for gametophytes,100?200?400?800mg·kg^-11 for seedlings?contaminated soil,to study the effrct of the physiological property of gametophytes and seedlings,enzyme activity and microbial community structureof three Cyatheaceae gametophytes rhizosphere soil.In order to provide theoretical basis for the damage mechanism of Cd²⁺,Pb²⁺stress on Cyatheaceae plants,and provide reference for the further protection of Cyatheaceae.The study tells that:?1?Different concentrations of Cd²⁺and Pb²⁺stress resulted in morphological changes of gametophyte cell integrity,chloroplast,sex organ and pseudo-root of three species of Cyatheaceae gametophyte,resulting in structural changes and loss of selective permeability,photosynthetic capacity and other functions.?2?With the increase of Cd²⁺,Pb²⁺stress concentration,the photosynthetic system and membrane system of three kinds of Cyatheaceae gametophytes and seedlings were damaged to some extent.The increase of protective enzymes activity at low concentration effectively reduced the degree of plant injury,but the protective effect of protective enzymes system at high concentration was very limited.The order of resistance of three kinds of Alsophila to Cd²⁺,Pb²⁺was Alsophila gigantea>Sphaeropteris lepifera>Alsophila costularis.?3?With the increase of Cd²⁺and Pb²⁺stress concentration,urease,phosphatase,dehydrogenase and catalase in rhizosphere soil of three kinds of Cyatheaceae gametophytes were all affected to some extent.Some enzymes were promoted at low concentration,and inhibited at high concentration.?4?The study on functional diversity of soil microbial community showed that different concentrations of Cd²⁺and Pb²⁺could increase the richness of microbial community in rhizosphere soil of Sphaeropteris lepifera and Alsophila costularis gametophyte,but the total number of microbial community decreased,while the correlation effect of Cd²⁺and Pb²⁺on Alsophila gigantea was on the contrary,which showed that the richness of microbial community decreased and the number of microbial community increased.?5?The study on the composition of soil bacterial community showed that under the stress of Cd²⁺and Pb²⁺with different concentrations,the dominant bacteria in rhizosphere soil of Alsophila gigantea were Bacillus,while the dominant bacteria in rhizosphere soil of Alsophila costularis and Sphaeropteris lepifera did not appear.Combined with the above results,this study concluded that Cd²⁺,Pb²⁺stress would have a certain impact on the reproductive development and soil environment of three species of Cyatheaceae,and the degree of impact increased significantly with the increase of concentration.Gametophytes are more sensitive to Cd²⁺,Pb²⁺stress than seedlings.The process of spermatocyte development into mature sperm may be the most sensitive link to Cd²⁺,Pb²⁺stress in Cyatheaceae alternating generations.In this study,the effects of heavy metals on Gametophytes of Cyatheaceae plants were studied for the first time by morphological characteristics,physiological characteristics and rhizosphere soil microecology.The results showed that Cd²⁺,Pb²⁺had certain effects on the growth and reproduction of Cyatheaceae plants and soil environment,and their effects on soil microecology would aggravate the damage of heavy metals to plants.