高温胁迫对一品红光合作用与叶绿素荧光的影响

以一品红威望为试验材料,研究45和50℃高温处理0～2 h对一品红叶片光合作用及叶绿素荧光参数的影响.结果表明:2种高温处理0.5 h时,一品红叶片的净光合速率(P_n)均大幅下降,但此后45℃处理的P_n缓慢回升,而50℃处理的P_n则不断下降,最终为负值;叶绿素荧光参数的变化表明,45℃高温处理导致一品红叶片光系统Ⅱ(PSⅡ)反应中心失活,可能为部分可逆失活,而50℃高温处理导致的PSⅡ反应中心失活可能为不可逆失活.说明一品红对高温有较强的耐受性,45℃短期高温对其伤害是可逆的,但50℃以上的高温会对其造成不可逆的伤害.高温胁迫初期,一品红叶片能够以热的形式耗散过剩的光能,这可能是一品红在高温逆境下的一种自我保护机制.

Effects of high temperature stress on photosynthesis and chlorophyll fluorescence of Euphorbia pulcherrima

The effects of high temperature stress on the photosynthesis and fluorescence parameters of poinsettia leaves treated with 45℃ and 50℃ for 0-2 h were studied in this paper.The results showed that the net photosynthesis(P_n)decreased gradually after 0.5 h in 45℃ and 50 C treatment,then P_n increased slowly in the former treatment,but decreased continuously in the latter treatment and reached to negative value; The photosynthesis decrease under high temperature stress was resulted from non-stomatal limitations,and the sensitivity of transpiration to stomatal conductance was higher than that of photosynthesis;The changes of the chlorophyll fluorescent parameters showed that the inactivations of PSⅡ reaction centers in poinsettia leaves were partly reversible after being treated with 45℃,b irreversible after being treated with 50℃.The above results showed that poinsettia had stronger resistance to high temperature,but it would suffer irreversible injure when being treated with 50℃.The poinsettia could dissipate excessive energy efficiently through heat dissipation in the early stage of high temperature stress,and this maybe the main self-protection mechanism of poinsettia from damaging by high temperature.