【摘要】 为了研究短期太阳紫外辐射对钝顶螺旋藻的影响,作者将静止和充气培养的藻体,暴露在全波长太阳辐射PAB(PAR+UVA+UVB),去除UVB辐射PA(PAR+UVA)及切断所有紫外辐射的光合有效辐射P(PAR)三种光处理条件下,测定了其光化学效率的变化。结果表明,紫外辐射(UVP)及光合有效辐射(PAR)均能导致钝顶螺旋藻的光化学效率降低,表现出了明显的光抑制,但是,UVR可导致更大程度的光抑制。充气培养条件下,与早晨(07:00)初始值相比,PAR导致了11%~20%的光抑制,而UVR(PAB-P)所产生的额外光抑制占9%~31%;静止培养条件下,UVR的存在使得螺旋藻的光化学效率趋近于零(无法检出)。在两种培养条件下,藻细胞所受最大光抑制均发生在中午,下午(17:00)表现出不同程度的恢复。紫外辐射使得类胡萝卜素及藻蓝蛋白与叶绿素a含量的比例增大。与PAB和P相比,PA处理使得螺旋藻类胡萝卜素和藻蓝蛋白与叶绿素含量之比明显升高,UVA可能会诱导类胡萝卜素及藻蓝蛋白的合成。更多还原

【Abstract】 Continuous depletion of the stratospheric ozone layer results in increasing solar ultraviolet radiation(UVR)reaching the earth’s surface.Which has been considered to affect living organisms.Solar UVR may also affect a variety of physiological and biochemical processes in the economic cyanobacterium,Spirulina platensis.However,little has been documented on this aspect.The present study evaluated the short-term effects of UVR on photochemical efficiency of S.platensis in aerated and non-aerated cultures while exposing it to full-spectrum solar radiation(PAB),solar radiation depleted of UVB(PA)and solar radiation deprived of total UV(P:PAR).It was found that both UVR and PAR inhibited the photochemical efficiency during noontime(11:00-13:00),however,UVR+PAR(PAB)resulted in higher inhibition. In aerated cultures,PAR resulted in 11%～20% compared to the initial value in the morning(07:00),UVR(PAB-P)brought about 9%～31% extra photoinhibition.While in non-aerated cultures,the photochemical effciency could not be detected when exposed to UVR.The greatest inhibition was observed at noontime,and the recovery was achieved in late afternoon(17:00)in both the aerated and non-aerated cultures.UVR increased the ratio of carotenoids or phycocyanin to chlorophyll a.Compared with PAB and P treatments,cells exposed to PA showed higher values of the pigment ratios,indicating a possibility that UVA may enhance the synthesis of carotenoids and phycocyanin.Although S.platensis was negatively affected by UVR,it tended to develop mechanisms counteracting the damaging effects of UVR during this short-term exposure period,such as down-regulation of the photosynthetic activity of accumulation of the carotenoids.更多还原