温室条件下UV-B辐射对蓝藻结皮生长和超微结构的影响

UV-B辐射是野外蓝藻结皮经常面临的一种环境胁迫因子.报道了温室条件下UV-B辐射对蓝藻结皮形态、生理和超微结构特征的影响.在本研究中,首先通过接种具鞘微鞘藻和爪哇伪枝藻形成初始蓝藻结皮,接着以初始蓝藻结皮为材料进行3种辐射处理:光合有效辐射、UV-B辐射+光合有效辐射和N-乙酰半胱氨酸+UV-B辐射+光合有效辐射.在...

Effects of UV-B radiation on growth and ultrastructures of cyanobacterial crusts under greenhouse conditions

UV-Bradiation may be an environmental stress commonly experienced by cyanobacterial crusts growing in desert areas. Here we report the effects of UV-Bradiation on the morphological and physiological changes and ultrastructural characteristics of cyanobacterial crusts. In this study,firstly the initial cyanobacterial crusts were formed by inoculating Microcoleus vaginatusGom. and Scytonema javanicum(Ktz.) Born et Flah onto loose sand in Petri dishes. Then,the initial cyanobacterial crusts were exposed to three different radiation treatments as follows:photosynthetically active radiation (PAR),UV-B+PARand N-acetylcysteine (NAC) +UV-B+PAR. On the 1st,3rd,6th,9th,12th and 20th days during the UV-Bradiation experiments,photosynthetic activities (optimal quantum yield,F_v//F_m),chlorophyll a,scytonemin and exopolysaccharide (EPS) contents of the crusts were examined. Crust color,crust shape,crust thickness and crust pHas well as crust dry weight were all determined. We also observed the ultrastructure properties of the cyanobacterial crusts under PARand UV-B+PARtreatments by means of scanning electron microscopy (SEM). The results indicated that the applied UV-Bdose had long-lasting negative effects on the cyanobacterial crusts. F_v//F_m of the cyanobacterial crusts was completely inhibited by UV-Bradiation,which meant UV-Bradiation had evident photoinhibition effects on the crusts. Chlorophyll acontent of the crust treated with UV-Bradiation was significantly lower than that of the crust under control conditions. In the case of UV-Bexposure,scytonemin of the cyanobacterial crusts was not inhibited by UV-Band on the contrary UV-Binduced a marked increase in scytonemin. Furthermore,the EPS content of the crust under UV-Btreatment presented a significant decline as compared to the control crust (p<0.05). Obvious destruction of ultrastructures was observed from the cyanobacterial crust subjected to UV-Bstress,and many changes in morphological characteristics of the crust under UV-Bradiation were also detected. Further,our results showed that NAC addition could provide effective protection to the photosynthetic activity of the crust under UV-Bradiation and the levels of chlorophyll aand EPSwere also promoted due to NACaddition,which meant that NAC might function as an effective antioxidant and could protect the cyanobacterial crust from oxidant stress induced by UV-Bradiation. The aim of this study was to discuss the responses of cyanobacterial crusts to UV-Bradiation and to improve understanding of toleration restriction of the crusts against UV-Bradiation,which may provide academic and practical significances for cyanobacterial crust applications in desertification control.