UV-B辐射增强与O_3胁迫对冬小麦光合特征的影响

Combination Effects of Enhanced UV-B Radiation and O_3 Stress on Photosynthetic Characteristics of Winter Wheat

为探明UV-B和O3复合胁迫对冬小麦光合作用的影响,开展了UV-B和O3单因子及其复合的大田开顶式气室(OTC)试验(CK,自然空气和UV-B辐射强度;T1,O3含量100 nmol.mol-1±9 nmol.mol-1;T2,UV-B辐射强度相对CK增加10%～10.9%;T3,复合处理组),利用LCpro+光合仪和DIVING-PAM叶绿素荧光仪,测定了不同生育期冬小麦(扬麦16)的气体交换参数和叶绿素荧光参数.结果表明,T1、T2和T3处理冬小麦的Pn、Gs、Tr、Pm和Ik较CK均显著下降,但T3与T1和T2之一或两者在大部分生育期均无显著差异.T2对冬小麦气孔开放和蒸腾作用的抑制程度显著大于T1,而在拔节期T1的Gs和Tr还较CK均显著增加;在整个生育期T1对冬小麦暗呼吸作用(Rd)均有促进,而T2、T3的Rd在大部分时期与CK无差异.T1和T2的Fv/Fm只在孕穗期显著下降,T3除拔节期外均显著低于CK;而T1、T2和T3处理的qP较CK均显著下降,且降幅满足T3>T1>T2.T1、T2和T3处理的NPQ、Y(NPQ)和Y(NO)较CK显著增加,最大增幅满足T3>T1>T2,其中T1和T2的NPQ在灌浆期转而较CK显著下降,而T3的NPQ在扬花期之后即显著下降,且T3的降幅显著大于T1和T2.T1、T2和T3处理的Y(Ⅱ)较CK均显著下降,且降幅满足T3>T1>T2.由此可见,UV-B和O3单因子及其复合胁迫下,冬小麦的气体交换能力、潜在光合能力和光合活性显著下降,光保护机制受到破坏,光能向调节性尤其是向非调节性热耗散的方向分配的比例显著增加,导致冬小麦受到UV-B和过剩光能、O3和过剩光能的双重伤害,并且UV-B和O3对PSⅡ的光保护机制和光能分配存在较为明显复合效应,但复合效应小于两者单独作用时负效应的累加.

Experiments were conducted under open-top-chambers conditions to assess the photosynthetic responses of wheat plants（Triticum aestivum L.,YangMai16） to supplemental UV-B radiation（10%-10.9% higher then control group,T1） and enhanced ozone [（100±9） nmol·mol-1,T2],separately and in combination（combination treatment,T3）,making use of LCpro＋ Portable Photosynthesis System and DIVING-PAM Fluorometer to determine gas exchange and chlorophyll fluorescence parameters.Results indicated that Pn,Gs,Tr,Pm and Ik of T1,T2 and T3 treatments decreased significantly compared to CK（control group,natural air and UV-B radiant intensity condition）,while there were no differences between T3 and T1 or T2 or both in major growth stages.UV-B fiercely inhibited the stomatal conductance and transpiration of plants,while T1 stimulated stomata opening and transpiration in jointing stage.Dark respiration（Rd） of T1 was increased,while no significance difference was found between T2 and CK or T3 and CK in most stages.T1 and T2 reduced Fv/Fm value only in booting stage,while T3 was significant lower than CK except jointing stage.qP value declined significantly in treatments of T1,T2 and T3 as Compared to CK,with decreasing amplitude occurring in the order T3T1T2.NPQ,Y（NPQ）,Y（NO） value of T1,T2 and T3 treatments increased significantly compared to CK,with maximum increasing amplitude occurring in the order T3T1T2,of which NPQ of T1 and T2 turned to decrease since filling stage,and T3 turned to decrease since flowering stage to a greater degree than T1 and T2.T1,T2 and T3 also caused significance reduction in Y（Ⅱ）,with reducing amplitude occurring in the order T3T1T2.Obviously,supplemental UV-B radiation and enhanced ozone caused a significant decrease in gas exchange capacity,maximum photochemical capacity and photosynthetic activity of winter wheat,and the photoprotective mechanism was damage,leading to greater proportion of excitation energy dissipated in the form of non-regulated heat and fluorescence.The photosystems of winter wheat were damaged by both excess energy and UV-B or excess energy and O3,or excess energy,UV-B and O3together.UV-B and O3 in combination enhanced the negative effects on photo-protective mechanisms and excitation energy distribution in PSⅡ compared to UV-B or O3 alone,while the interactive effects were less than addition.