低盐胁迫下模拟酸雨对裂片石莼光合作用生理特性的影响

为探讨低盐胁迫下模拟酸雨对裂片石莼光合作用、抗氧化活性等生理特性的影响,实验设置3个盐度梯度、2个p H水平,运用叶绿素荧光仪、液相氧电极等仪器测定叶绿素荧光参数和光合放氧速率,采用氮蓝四唑法、考马斯亮蓝G250法及蒽酮硫酸比色法测定超氧化物歧化酶(SOD)活性、可溶性蛋白和糖含量。结果发现:(1)模拟酸雨(pH 4.4)处理显著抑制了裂片石莼的生长,且受盐度的影响。p H 8.1、盐度10处理的裂片石莼具有较高的生长速率;盐度越高,模拟酸雨的影响越大。(2)模拟酸雨(pH 4.4)处理显著抑制了裂片石莼的最大光合效率(F_v/F_m)和有效光化学效率(F_v′/F_m′),但受盐度的影响不显著;模拟酸雨和低盐度协同降低了裂片石莼的最大相对电子传递速率(rETRmax)。(3)模拟酸雨(pH 4.4)降低了裂片石莼的暗呼吸和光合放氧速率,但受盐度的影响不显著。(4)正常盐度及正常p H处理的裂片石莼SOD活性最高;在盐度(10、25)处理下,模拟酸雨抑制了裂片石莼的SOD活性;而在盐度5处理时,模拟酸雨提高了SOD活性。(5)相对于海水正常p H处理,模拟酸雨显著降低了裂片石莼可溶性蛋白含量,但其可溶性糖含量显著提高,尤其是在低盐条件下。研究表明,模拟酸雨对裂片石莼生长的影响受海水盐度的调控,这在一定程度上也将影响近岸海域大型海藻的生态群落组成。

Effects of simulated acid rain on the photosynthetic physiological characteristics in Ulva fasciata under salt stress

Ulva fasciata, an extremely rich wild seaweed in natural resources, has a high agricultural and medicinal value. They can also absorb large amounts of nitrogen, phosphorus and other nutrients, and can be used for aquaculture wastewater treatment and the culture environment improvement. With the rapid economic development, industrial pollution gradually increased, the effects of acid rain on terrestrial ecosystems and their harm have received widespread concern, while the effects of acid rain on the photosynthetic physiology of macroalgae in the intertidal zone have barely been studied. This study was to examine the effects of simulated acid rain on the physiological characteristics, including growth rate, chlorophyll content, chlorophyll fluorescence parameters, soluble protein and carbohydrate contents, and antioxidant activities, in hyposaline-grown alga Ulva fasciata. Three salinities (5, 10 and 25) and two levels of pH (4.4, 8.1) were set in the experiment. The water-pulse amplitude modulated fluorometer, liquid oxygenelectrode, and NBT, coomassie brilliant blue G250 and anthrone colorimetric method were used to determine the combined effects of simulated acid rain and salinity on the macroalgae U. fasciata. (1) The growth of U. fasciata was significantly inhibited by simulated acid rain (pH 4.4), and also affected by salinity of seawater. U. fasciata grown under moderate hyposaline (salinity 10) and normal pH(pH 8.1) showed the highest growth rate. The suppressive effect of simulated acid rain was enhanced by higher salinity. (2) Simulated acid rain (pH 4.4) significantly inhibited the maximum photosynthetic efficiency (F_v/F_m) and the effective photochemical efficiency (F_v''/F_m'') of U. fasciata, but the salinity showed no significant effects. The inhibitory effects of simulated acid rain and hyposalinity on the maximum relative electron transfer rate (rETRmax) of U. fasciata have had also been observed. (3) Simulated acid rain (pH 4.4) reduced the dark respiration and photosynthesis oxygen release rate of U. fasciata, but showed no significant difference between salinity treatments. (4) Under normal salinity (25) and pH (pH 8.1) conditions, U. fasciata showed the highest SOD activity. Under relatively high salinity (10, 25) treatment, simulated acid rain inhibited the SOD activity of U. fasciata, while under salinity 5 treatment, simulated acid rain increased the SOD activity. (5) Compared with the treatment of pH 8.1, simulated acid rain significantly reduced the soluble protein content of U. fasciata, but the soluble polysaccharide content increased significantly, especially under hyposaline conditions. The effects of simulated acid rain on the physiology of U. fasciata were regulated by seawater salinity. Under the global climate change scenario, the increase of acid rain and salinity might influence the ecosystem of macroalgae grown in the intertidal niches, nearshore ponds and the estuaries.