The Injury Mechanism Of Chloroplast Of Two Kinds Of Chlorococcum Irradiated By Heavy Ions Beam

With the rapid development of aerospace technology, the influence of life activity attracts more attention because of outspace environment intense radiation. Algae as junior producer in ecosystem, had efficient photosynthesis to generate substance and oxygen, so algae is considered as one of most important part in constructing the environment in long-term manned space activities. Therefore, it is meaningful for investigating the important organelle chloroplast in algae cell irradiated by the heavy ions beam, which is produced by ground accelerater and similar with the outerspace rays. Above all, this paper pays more attention to study the four parts as following:the short-term influence of photosynthsis pigments(chlorophyll a, chlorophyll b and carotenoid) and antioxidant sysytem of Scenedesmus quadricauda and Selenastrum capricornutum irradiated by heavy ions beam; screening the mutant strains which have different growth rate and photosynthsis content; investigating the change of Dl protein of mutant strains which is key protein for PS Ⅱ reaction center under coupling with high light; exploring the change of soluable protein in mutant strains.After investigating the short-term effect of chloroplast of Scenedesmus quadricauda and Selenastrum capricornutum irradiated by heavy ions beam, we found that it also has a phenomenon about "low promoting and high inhibiting", which was similar with results of other traditional radiative rays, and that was the photosynthesis pigments could recover to the control level in short term for low dose group, while the high dose group injury severely and could not recover in short term. Second, after determination of MDA content, we found that the lipid membrane of algae cell also damaged after radiation. For lose dose group, the lipid membrane injured slightly, it could be repaired in48h because of antioxidant system taking effect on removing ROS, while for high dose group, the antioxidant system could not have function on repairing the injury of lipid membrane, so the injury could not be repaired in48h.After preliminary screening the mutant algae strains irradiated by heavy ions beam, we got the strains which had different gorwth rates and strain colcors, and it included9stains of Scenedesmus quadricauda and5stains of Selenastrum capricornutum which growed more faster than control group. In addition, determining the lethal rate of the two kinds of algae, it presents exponential growth trend and not like "saddle type", which is relatively common in other biological materials’lethal curve.After determining the chlorophyll-a content of mutant strains in second screening, we found that the chlorophyll-a content of mutant strains were lower than the control group. Measuring the change of D1protein coupling with high light, we found that the content of D1protein which photosynthsis pigments injured presented increasing first and decrease significantly following the time of high light exposure. In addition, the content of D1protein which photosynthsis pigments enhanced significantly presented still higher than the control group under high light or tied with the control. Therefore, the results presented the PS Ⅱ reaction center had injured in degree under heavy ions radiation.Determining the absorbance of mutant strains in logarithmic phase, it could present the change of biomass indirectly, so we could found the accumulation of soluable protein. From the results, we got biomass of No.7mutant strain of Scenedesmus quadricauda accumulated much more than the control group, while biomass of No.1and No.12strains were less than the control group significantly. For the mutant strains of Selenastrum capricornutum, biomass of No.25strain accumulated more than the control group, while biomass of No.13, No.15and No.26were less than the control group. At the same time, for accumulation of biomass strains, we investigated the content of soluable protein, but we could not find the strains accumulate more soluable protein than the control which biomass also increased, so there was no strain suitable for zooplankton as feed.