光强对缘管浒苔(Ulva linza)光合生理特性和短期温度效应的影响

EFFECTS OF LIGHT INTENSITY ON PHOTOSYNTHETIC PHYSIOLOGY CHARACTERISTIC AND SHORT-TIME TEMPERATURE REACTION OF ULVA LINZA

由于季节和分布深度的不同,海藻接受的光强和温度也不同,其生理响应机制也不同。本文旨在研究不同光强对缘管浒苔(Ulvalinza)光合生理特性及短期温度效应的影响。缘管浒苔样品采自连云港高公岛海区(119.3°E, 34.5°N)。实验设置了低、中、高三个不同水平的光强,分别为90、200和400μE/(m^2·s)。结果表明,藻体的净光合作用速率在低光下显著低于培养在高、中光下的,而光强对呼吸作用速率无显著影响。高光下藻体光系统Ⅱ的最大光化学效率(F_v/F_m)值显著低于中、低光强下,而非光化学淬灭(NPQ)值随光强降低显著下降。叶绿素a和叶绿素b的含量在低光强下均显著高于高、中光强下的含量。最大相对电子传递速率(rETR_(max))随光强变化显著,中光下最高,低光下最低;饱和光强(I_k)在低光下显著低于在高、中光下。在不同浓度的溶解性无机碳(DIC)下,净光合作用速率在不受碳限制时所能达到的最大速率(V_(max))随光强升高而显著增大,净光合作用速率为最大速率一半时的底物浓度(K_m)在低光下显著低于高、中光下。这表明低光上调了藻体的无机碳利用能力。短期温度实验表明,高光培养下,酶失活一半时的温度(T_h)显著增加,而低光下藻体的净光合作用速率的最适温度(T_(opt))显著降低,这表明低光显著提高了缘管浒苔对环境的敏感性,而高光下的藻体更适应高温的环境,这为绿潮在5—7月份大规模暴发的现象研究提供了一定的理论参考依据。

Seaweeds receive a different light intensity and temperature in a different season and/or depth,resulting in different physiological responses.We studied the impacts of light intensity on photosynthetic physiological characteristics and on short-term temperature effects of green algae Ulva linza.Samples of U.linza were collected in the Gaogong Island of Lianyungang,Jiangsu(119.3°E,34.5°N).Three light intensities of low,medium,and high were tested,which were 90,200,and 400μE/(m2·s),respectively.The results showed that the net photosynthetic rate of the algae under the low light intensity was significantly smaller than those under high and medium light intensities,and the light intensity showed no significant effect on the respiration.Under the high light intensity,the maximum photochemistry efficiency(Fv/Fm)value of the algae was significantly smaller than those under medium and low light intensities,and the non-photochemical quenching(NPQ)value decreased significantly with a decrease of light intensity.In addition,under the low light intensity,the contents of chlorophyll a and b were significantly greater than those under high and medium light intensities.The maximum relative electron transfer rate(rETRmax)varied significantly with the light intensity,being the highest under the medium and the lowest under the low light intensity.The saturation light intensity(Ik)under the low light intensity was significantly smaller than those under high and medium light intensities.At a different concentration of dissolved inorganic carbon(DIC),the maximum rate(Vmax)of net photosynthesis with no carbon limitation increased significantly with the increase of light intensity,and under a low light intensity,the substrate concentration at half of the maximum net photosynthetic rate(Km)was significantly lower than those under high and medium light intensities.Under the low light intensity,the inorganic carbon utilization capacity of the algae bodies upregulated.Our experiments on short-term temperature effect showed that the temperature(Th)at which half of the enzymes inactivated under high light intensity increased significantly,while the optimal temperature(Topt)of net photosynthesis rate of the algae under low light intensity decreased significantly.This indicated that low light intensity could improve significantly the sensitivity of the algae to an ambient temperature change,and algae under high light intensity were stronger against a high temperature.Therefore,this study could offer a theoretical reference for understanding a large-scale outbreak of green tide from May to July in the study area.