Chen Gui-zhu

Physiological adaptability of three mangrove species to salt stress

Abstract The impact of salinity on three arboreal mangrove plants, Sonneratia apetala ( Sa ), S. caseolaris ( Sc ) and Rhizophora stylosa ( Rs ), was studied. The three mangrove species were treated with different salinity levels over a three-month period. The response and adaptation of these three mangrove species to salinity were shown to be different. Net photosynthesis rate, stomata conductance and transpiration rate of leaves decreased and soluble sugar content in leaves increased, with salt concentration in all three mangrove species. The malondial dehyde (MDA) content in stems and leaves of Sa and Sc somewhat decreased when the salinity was lower than 10, but rapidly increased with increasing salt concentration. The MDA content in stems and leaves of Rs increased only when salinity was greater than 40. No changes were observed in the MDA content of roots in the three mangrove species. The adaptabilities of Sa and Sc to salt tolerance were limited. The more salt tolerant the mangrove Rs , the more likely the free oxygen radicals were eliminated through the increase in activity of superoxide dismutase (SOD). Results of this experiment identified salinity levels best suited for the growth and metabolism of the species, which provides information necessary for maintaining mangrove forestation along the South China coast.

Arsenic tolerance, uptake and translocation by seedlings of three rice cultivars

Abstract By simulating the anaerobic conditions with agar nutrient solutions, effect of arsenic (As) on the growth and As uptake by hybrid, conventional and glutinous rice cultivars were studied. It showed insignificant effect of As on the root dry weights of three rice cultivars when treated by As of different concentrations. The shoot dry weights of hybrid and glutinous decreased with As concentrations increasing, while low concentrations of As (0.5 mg L−1) could enhance the growth of conventional rice. Generally, As concentrations in roots and shoots increased as As concentrations of treatment solutions increasing. The root system had strong ability to uptake and accumulate As. The root As concentrations ranged from 156 to 504 mg kg−1, representing 63.40%–81.90% of the total As concentrations in rice, which were much higher than shoot As concentrations. The fact that the glutinous rice had higher biomass, higher tolerance, and lower As concentrations in its roots and shoots than the other two rice cultivars proved that the glutinous rice was more applicable to As-polluted soils.

Response of microbial communities to phytoremediation of nickel contaminated soils

Through pot experiment, effects of phytoremediation on microbial communities in soils at different nickel treatment levels were studied. Two Ni hyperaccumulating and one Ni tolerant species were planted in paddy soils different in Ni concentration, ranging from 100 to 1 600 mg/kg. After 110 days of incubation, soil microbial activities were analyzed. Results showed that populations of bacteria, fungus, and actinomycetes and biomass of the microorganisms were stimulated when nickel was added at a rate of 100 mg/kg in non-rhizospheric soil. When the rate was over 100 mg/kg in the soil, adverse effects on the soil microbial communities were observed. The plantation of Ni hyperaccumulating species could increase both the population and biomass of soil microorganisms, because, by absorbing nickel from the soil and excreting root exudates, the plants reduced nickel toxicity and improved the living environment of the microbes. However, different plant species had different effects on microorganisms in soil.Randomly Amplified Polymorphic DNA (RAPD) with five primers was used in this study in 25 soil samples of four types of soils. A total of 947 amplified bands were obtained, including 888 polymorphic bands and 59 non-polymorphic bands. The results indicated that the composition of microbial DNA sequences had changed because of the addition of nickel to the treated soils. Shannon-Weaver index of soil microbial DNA sequences reduced in the nickel contaminated soils with increasing nickel concentration. The changes in Shannon-Weaver index in the four types of soils ranged from 1.65 to 2.32 for Alyssum corsicum, 1.37 to 2.27 for Alyssum murale, 1.37 to 1.96 for Brassica juncea, and 1.19 to 1.85 for nonrhizospheric soil. With the same amount of nickel added to soils, the Shannon-Weaver index in rhizospheric soil with plants was higher than that in non-rhizospheric soil.