CO_(2)浓度与温度升高对冬小麦叶片光合与快速叶绿素荧光特征的影响

Effects of elevated CO_(2) concentration and increased temperature on the photosynthesis and fast chlorophyll fluorescence of winter wheat leaves

为研究CO_(2)浓度和温度升高对小麦叶片光系统Ⅱ(PSⅡ)性能与光合特性的影响,以盆栽冬小麦‘郑麦9023’为材料,通过气候变化人工模拟控制室设置不同CO_(2)浓度(400与600μmol·mol^(-1))与温度(室温与室温+2℃),测定小麦关键生育期叶片的光合特征曲线(P_(n)-PAR曲线、A-C_(i)曲线)与快速叶绿素荧光诱导动力学曲线(OJIP曲线),分析光合性能的变化特征。结果表明:增温条件下,小麦旗叶叶绿素a、b和类胡萝卜素浓度在开花期较对照显著增加,但最大电子传递速率(J_(max))与最大净光合速率(P_(max))无显著变化,最大羧化速率(V_(max))与V_(max)/J_(max)降低。CO_(2)浓度升高及其与增温的叠加作用下叶绿素浓度无显著变化,P_(max)、J_(max)与V_(max)较对照显著升高,但叠加效应下P_(max)与J_(max)提升幅度降低。增温下小麦PSⅡ综合性能指数(PI_(ABS))显著受到抑制,主要是由于PSⅡ反应中心闭合程度(V_(j))增加,受体侧损伤,使单位反应中心和单位横截面积电子传递能力(ET_(o)/RC、ET_(o)/CS_(m))降低,引起电子传递量子产额(Ψ_(Eo))减少。CO_(2)升高下,虽然ET_(o)/RC也受到抑制,但由于单位面积有活性的PSⅡ数目(RC/CS_(m))增加,QA被还原速率下降,所以PI_(ABS)得到增强。二因素叠加作用下,PSⅡ供受体侧电子传递性能(W_(k)、V_(j)、Mo)较单一增温处理得到改善,因而PI_(ABS)较对照没有显著降低。因此,温度持续升高2℃可显著抑制冬小麦叶片光合系统电子传递能力,而CO_(2)浓度升高扩大了PSⅡ反应中心的开放程度,增强了供受体侧电子传递能力,对增温产生的光合抑制具有一定的缓解作用。

A pot experiment was conducted to examine the effects of elevated CO_(2) concentration([CO_(2)])and increased temperature on photosynthesis and PSⅡperformance of the leaves of winter wheat(Triticum aestivum)cv.‘Zhengmai9023’in controlled environment chambers.The performance of photosystem(PS)Ⅱand the electron transport were evaluated by using OJIP induction curves of chlorophyll a fluorescence,A-C_(i) curve and P_(n)-PAR curve under a full factorial combination of[CO_(2)][400μmol·mol^(-1)(CK)or 600μmol·mol^(-1)(eC)]and temperature[normal or normal+2℃(eT)].The results showed that the eT treatment significantly increased the concentration of chlorophyll a,b and carotenoids,but did not affect the maximum net photosynthetic rate(P_(max))or the maximum electron transfer rate(J_(max)),and decreased maximum carboxylation rate(V_(max))and V_(max)/J_(max).The eC and eCeT treatments had no significant effect on the concentration of chlorophyll a or b,but significantly increased P_(max),J_(max) and V_(max) compared with CK.The eT treatment damaged the electron transporter on the acceptor side,increased the closure degree of PSⅡcenters(V_(j)),and decreased the electron transport flux from QA to plastoquinone(ET_(o)/RC,ET_(o)/CS_(m))and quantum yield for electron transport from QA to plastoquinone(Ψ_(Eo)),thereby significantly inhibiting the PSⅡperformance(PI_(ABS)).The eC treatment decreased ET_(o)/RC,but increased the density of active PSⅡreaction centers(RC/CS_(m))and decreased the reduction of QA,thus improving the PI_(ABS) consequently.Under eCeT treatment,the electron transport performance of PSⅡdonor side and acceptor side were improved(W_(k),V_(j),Mo)compared with eT,so PI_(ABS) was unaffected compared with CK.In summary,the electron transport performance in winter wheat leaves were significantly inhibited by persistent increase in temperature.This inhibition could be partially alleviated by elevated CO_(2) concentration.