铯对小麦叶片光合特性影响的研究

随着环境中铯(Cs)污染日益恶化,铯对生物毒害作用的研究受到越来越多的关注.为了探讨铯对植物光合作用的影响,在石英砂和Hoagland营养液培养体系下,从三叶期开始用浓度为0、0.5、1、5、10、20 mmol·L-1的133Cs+[CsCl]处理小麦(Triticum aestivum L.)幼苗.在处理后的第0、7、14、21、28 d时,检测小麦光合特性的改变.结果表明:用0.5 mmol·L-1和1 mmol·L-1低浓度133Cs+处理7 d后,小麦叶片的叶绿素含量、叶圆片放氧活性、类囊体膜电子传递活性均显著高于对照;但随133Cs+浓度的增加及处理时间的延长,这些参数的数值均显著下降.此外,光合系统II(PSII)活性的下降速率高于光合系统I(PSI)下降速率,说明PSII相对于PSI更容易受到133Cs+的胁迫伤害.这些结果表明133Cs+对小麦的毒害效应受时间和浓度的双重制约.低浓度133Cs+可以促进小麦光合作用,而高浓度133Cs+则显著抑制小麦光合作用.

Effects of cesium on photosynthetic characteristics of wheat seedlings

With the worsening of the cesium contamination in soil and water,there has been a growing interest in the deleterious effects of cesium on organisms.In order to contribute to the understanding of the photosynthesis characteristics change induced by cesium,three-leaf stage wheat(Triticum aestivum L.) seedlings raised in quartz sand and Hoagland solution culture system,were provided with a nutrient solution with the supplement of different concentrations 133Cs+(0,0.5,1,5,10,20 mmol·L-1 133CsCl).Photosynthetic characteristics of wheat seedlings were determined after 0,7,14,21 and 28 d of treatment,respectively.When the wheat seedlings were exposed to both low 133Cs+ concentrations(0.5 and 1 mmol·L-1) for 7 d,the chlorophyll content,oxygen-evolving activities of both leaf discs and the electron transport activities of thylakoid membranes increased firstly,and along with elevated levels of applied 133Cs+ as well as the duration of treatment,all the parameters then decreased significantly compared with the control.Additionally,-for the electron transport activities of thylakoid membranes,PSII drop faster than PSI,and this result indicated PSII is more susceptible to the injury of 133Cs+ compared with PSI.All the results obtained from this investigation showed that the deleterious effects of 133Cs+ on the wheat seedlings is restricted by both 133Cs+ concentrations and the duration of exposure.For the wheat seedlings employed in our study,low 133Cs+ concentrations promoted the photosynthesis,and high 133Cs+ concentrations inhibited photosynthesis.