遮阴和臭氧浓度增加对冬小麦叶片光合作用的影响

Effect of Elevated O_3 Concentration and Shading on Photosynthesis of Winter Wheat′s Leaves

基于开顶式气室(OTC),开展了遮阴和不同臭氧熏蒸水平的大田试验(不遮阴+空气,CK;不遮阴+100 nL·L-1O3,T1;不遮阴+150 nL·L-1O3,T2;20%遮阴+空气,T3;20%遮阴+100 nL·L-1O3,T4;20%遮阴+150 nL·L-1O3,T5),并采用Diving-PAM叶绿素荧光仪测定了冬小麦(扬麦13)灌浆期不同叶位叶片的荧光参数,研究了遮阴和臭氧浓度增加对冬小麦灌浆期不同叶位叶片光合荧光特性的影响。结果表明,臭氧浓度增加显著降低了冬小麦灌浆期的Fv/Fm、Pm、Ik、qP和实际光量子效率Yield,提高了Y(NO)、L(PFD)和(1-qP)/NPQ,并使NPQ和Y(NPQ)先升高后降低;遮阴处理下的臭氧胁迫对冬小麦的影响程度则显著低于未遮阴下的臭氧胁迫,遮阴缓解了臭氧胁迫对冬小麦叶片造成的损伤。可见,臭氧浓度增加抑制了PSⅡ的电子传递活性,损伤了捕光系统和耗散保护机制,导致光合能力降低;遮阴则在一定程度上提高了PSⅡ的电子传递速率和处理过剩光的能力,缓解了臭氧对冬小麦光保护机制的破坏。另外,由于臭氧沉降的影响导致植株下部臭氧浓度过高,倒三叶受到胁迫影响最为严重,热耗散机制受到严重损伤。

In order to research the effect of elevated 03 concentration and shading on photosynthetic fluorescence parameters of the winter wheat＇s different leaves at grain filling stage, the different 03 fumigation and shading conditions（ natural light and ambient air, CK; natural light and 100 nL.L-I 03, T1; natural light and 150 nL＇L-1 03, T2; 20% natural light and ambient air, T3; 20% natural light and 100 nL.L-1 O3, T4; 20% natural light and 150 nL.L 1 03, T5 ） on chlorophyll fluorescence of winter wheat＇s（YangMai 13 ） different leaves at grain fill- ing stage were conducted via open-top chamber technique in conjunction with Diving-PAM fluorometer. The results showed that elevating 03 concentration significantly decreased F~/Fm.PmJk ,qP and the actual photochemical efficiency Yield of winter wheat at grain filling stage, Y （ NO ）, I~ erD） and （ 1 -qP）/NPQ rised, NPQ and Y （NPQ） increased and then decreased; the elevated 03 concentration with shading has sig- nificantly less effect on wheat than never shading, shading alleviate the damage caused by 03 stress on winter wheat leaves. Visible, elevated 03 concentration inhibited electron transport activity of PS I], injured light harvesting systems and dissipative protection mechanisms, result- ing in reduced photosynthetic capacity; shading enhanced the PS 1] electron transfer rate and the eapablility of treating the excess light, alle- viate the destruction caused by 03 stress on photoprotective mechanisms. Moreover, due to the impact of 03 settlement, the 03 concentration on the bottom of plant was too high, thus, the third leaf and the heat dissipation mechanism have been most severely damaged by 03.