【作者】 徐军田；

【导师】 高坤山；

【作者基本信息】 汕头大学 ， 海洋生物学， 2008， 博士

【摘要】 人类活动导致的区域以及全球性的环境变化,影响大型海藻的光合作用与生长。阳光紫外辐射（UVR）和CO2浓度变化如何调控海藻的生理学过程是近年来海藻环境生理学研究的焦点之一。本文以龙须菜和海萝两种经济红藻为研究材料,探讨了阳光紫外辐射和CO2浓度变化对其光合作用及生长的影响,并研究了CO₂和UVR对这两种藻类的耦合效应,其主要结果如下:龙须菜的生长,在CO₂浓度升高的条件下,受到促进,而在UVR存在的条件下,受到抑制。UV-A或UVB,在辐射强度较高时,都使得藻体生长减慢,而在阴天或较低辐射条件下,UV-A对生长有促进作用。UV-A对生长的促进作用,在低CO2浓度下较大,而在CO₂浓度（pCO2）升高（加倍）条件下,不显著。对紫外辐射有屏障作用的紫外吸收物质,受阳光辐射和CO2浓度变化的影响,紫外辐射增强与CO₂浓度升高,均能导致该类物质含量的升高,从而缓解了阳光紫外辐射的负面效应。进一步的研究表明,UV-A对龙须菜生长的促进作用与其对UV-A的利用有关。UV-A,在阳光辐射较低情况下促进光合作用,在滤除可见光的条件下,也能驱动光合放氧或固碳,其能量的传递是藻胆蛋白进行的;藻体对UV-A的利用效率、光补偿点及对无机碳的利用机制与在可见光下基本相同。海萝,区别于龙须菜,处于潮间带上部,经常在退潮时接受脱水的胁迫。本文研究发现,海萝在低潮干出状态下,其光合作用虽然受失水的影响,但在空气CO2浓度升高的条件下,受到促进。在轻微失水的情况下（10%左右）,藻体的光合作用达到最大,然后随着失水的增加而逐渐下降。UVR所导致的相对抑制率随着光强的增加而增大,但高浓度CO₂的存在能够缓解这种抑制作用。随着失水的增加,UVR对藻体的负面影响增大,而空气CO2浓度加富的条件下,该负面作用减小。更多还原

【Abstract】 Environmental changes in regional or global scales due to industrial activities affect photosynthesis and growth of seaweeds.How changing levels of UVR and CO₂ concentration influence the physiology of seaweeds becomes a focus of environmental physiology of algae.In this paper,the effects of UVR and CO₂ as well as their interactive impacts on the photosynthesis and growth of Gracilaria lemaneiformis and Gloiopeltis furcata,two economic red algae,were studied.The main results are as follows:The growth of Gracilaria lemaneiformis was enhanced by elevated CO₂ concentrations, while inhibited in the presence of UVR.Both UV-A and UVB,at high irradiance levels, inhibited the growth of the thalli,while UV-A stimulated it at reduced levels or on cloudy days. Such a UV-A enhancement of growth was significant only at the ambient level of CO₂ concentration,becoming insignificant under CO2-enriched（doubled atmospheric CO₂） condition. The UV-absrobing compounds in Gracilaria lemaneiformis increased at ither high CO₂ concentration or in the presence of UVR,playing protective roles against UVR damage.The enhancement of growth by UV-A was demonstrated to be associated with the photosynthetic utilization of UV-A waveband.UV-A enhanced the photosynthesis at moderate levels,it also drove photosynthetic O₂ evolution and carbon fixation even in the absence（filtered out） of PAR. Under UV-A alone,the thalli showed similar photosynthetic efficiency,light compensation point and carbon acquisition mechanism,as found under PAR.UV-A energy was suggested to be transferred by the phycobiliproteins,the major antenna pigments in red algae.Gloiopeltis furcata,in contrast to Gracilaria lemaneiformis,inhabiting the upper part of intertidal zone,often suffers from desiccation（dehydration） stress at low tide.During the emersion when the alga was exposed to air,its photosynthetic CO₂ fixation rate was raised by enriched CO₂ in the air,regardless of the negative effects of desiccation.Desiccation during the emersion increased photosynthesis at low levels of water loss（about 10%）,it reduced the rate at higher levels of water loss.The UVR-induced inhibition increased with increased solar radiation,but it became less under CO₂-enriched conditions.更多还原