汞对斜生栅藻(Scenedesmus obliquus)生长发育及光合作用的影响

汞对斜生栅藻生长的毒性阈值在0.02—0.05mg/l之间,生长完全受抑制的最低浓度在1—2mg/l之间。生长滞缓期随汞浓度提高而延长。0.05—1mg Hg~(2 )/l,能引起细胞体积增大、形态异常、似亲孢子形成方式紊乱等现象。其变异程度及持续时间随汞浓度提高而递增。形态变异的原因与汞抑制似亲孢子的形成,并扰乱其形成方式及发育有关。汞对光合作用有明显的影响,浓度在0.5mg/l以上时,其抑制作用在3小时内表现出来。0.01—1mgHg~(2 )/l,使光合强度在24小时内下降到约为对照的20—80％,抑制率与汞浓度成正相关,相关系数γ=0.993。迄后,有不同程度的恢复,仅0.01mg/l组在48小时内可恢复正常。分析认为,汞对光合作用及似亲孢子形成的抑制作用,是使生长滞缓期延长的重要原因。

EFFECT OF MERCURY ON GROWTH, DEVELOPMENT AND PHOTOSYNTHESIS OF SCENEDESMUSOBLIQUUS

The toxicity threshold of Hg on growth of S. obliquus is between 0.02 and 0.05mg/l. The minimum concentration which may induce complete growth inhibition is in the range of 1-2mg/l. And, the length of lag phase during growth depends on Hg content.Concentrations of 0.05^-1mg/1 Hg caused inhibition of autospore formation, disturbance of the mode of autospore formation and development, thus inducement of cellular abnormalities, e. g. increased cell size, the normally fusiform cells assuming an ovoid, oblong and aberrant irregular shape. The degree of abnormalities and duration are directly related to mercury concentration. There were no visible changes of morphology at 2mg/l but the chloroplast depigmentated gradually.0.01^-1mgHg²⁺/l causes decrease in photosynthetic activity to about 20-80% of control within a period of 24 hours. Degree of inhibition is, however, proportional to Hg level. The toxic effect of Hg concentrations greater than 0.5mg/l shows rapidly in 3 hours. At the end of experiment (48th hour) photosynthesis of all treatments except 1mg/1 exhibites different degree of recovery, but only at 0.01mg/l it recovers to a level that is similar to that of the control.The experimental results indicate that the lag in growth is due to inhibition of Hg on photosynthesis and autospore formation.