干燥-再吸水条件下爪哇伪枝藻生理特性和超微结构特征

以典型荒漠丝状蓝藻爪哇伪枝藻为材料,在温室中设置水合(对照)、轻微干燥、中度干燥和极度干燥4种处理,研究干燥胁迫对藻体光合活性、膜脂过氧化、细胞可溶性物质含量、抗氧化酶活性以及细胞超微结构的影响,并采用不同促进剂和抑制剂对干燥藻体进行再吸水处理,测定藻体光合活性的恢复情况。结果显示:(1)爪哇伪枝藻在干燥胁迫下PSⅡ最大光化学效率(Fv/Fm)显著降低,并与其藻体水分含量之间呈极显著性相关(r=0.97、P<0.000 1);(2)随着干燥胁迫程度增加,藻体MDA含量、SOD和CAT活性随之升高,细胞可溶性蛋白和可溶性糖含量增加;(3)在藻体再吸水条件下,培养液(BG-110)、胞外多糖和蔗糖对藻体Fv/Fm的恢复具有重要作用,N-乙酰半胱氨酸和脯氨酸对Fv/Fm有一定的恢复效果,氯霉素和敌草隆则抑制Fv/Fm;(4)与水合状态下的细胞结构相比,干燥藻体细胞结构发生明显的变化,如细胞壁增厚,原生质粘稠浓缩、呈紧密分层排列,细胞内出现大量细小黑色颗粒物等。(5)采用不同外源物质对干燥藻体进行再吸水时,藻体的光合活性呈现不同的恢复效果。研究表明,干燥胁迫下爪哇伪枝藻的光合活性受到明显抑制,细胞质膜过氧化程度加剧,细胞出现可溶性小分子物质积累,抗氧化酶活性增强,并造成细胞结构出现适应性变化。

Physiological Characteristics and Ultrastructures in Scytonema javanicum Subjected to Desiccation and Rehydration

Scytonema javanicum was a typical filamentous cyanobacteria and was selected for experimental material in this study.Concerning the experiments,the effect of dehydration on photosystem Ⅱ(PSⅡ) activity,membrane lipid superoxide,production of intracellular water-soluble substances and antioxidant enzyme activities as well as ultrastructures of S.javanicum were investigated in greenhouse by means of simulating desiccation treatments of hydration(as control),light desiccation,medium desiccation and severe desiccation.Furthermore,rehydration treatments on S.javanicum subjected to desiccation were conducted by using of different promotors and inhibitors to detect recovery effects of PSⅡ activity.The results showed that dehydration to S.javanicum resulted in an obvious restriction in maximum photochemical efficiency of PSⅡ(Fv/Fm) and highly significant correlation between Fv/Fm and water content was exhibited(r=0.943,P<0.000 1),and antioxidant enzyme activities such as SOD and CAT presented gradually increases along with intensification of desiccation degrees.It also showed that desiccation stress had a significantly deleterious effect on membrane lipid superoxide as assessed by measurement of MDA content and production of intracellular water-soluble substances such as saccharides and proteins were comparatively greater in the desiccated cells than that in the control cells.Moreover,rehydration to S.javanicum induces an apparent increase in Fv/Fm by additions of culture fluid(BG-110),EPS and sucrose,proline and NAC were found to have limited roles in Fv/Fm recovery.However,CMP and DCMU were observed to inhibit Fv/Fm recovery of S.javanicum.Additionally,cellular ultrastructures of the algal cells subjected to dehydration were found to generate obvious changes by comparison with the cellular structures under hydration treatment,such as thicker cellular wall and layered,compact and concentrated protoplasm,as well as abundant thin and dark refraction granules.The above research results indicated that desiccation stress brought about apparent inhibition of PSⅡ activity,aggravation of membrane lipid superoxide,accumulation of intracellular water-soluble substances and amplification of antioxidant enzyme activities as well as adaptive changes of cellular structures.In addition,there were some differences in PSⅡ activity recovery by means of different exterior substances to rehydration on the desiccated algal cells.