臭氧胁迫对冬小麦光合作用、膜脂过氧化和抗氧化系统的影响

在大田试验的条件下,利用开顶式气室(OTC)研究了臭氧胁迫对冬小麦不同生育期(拔节期、孕穗期、扬花期和灌浆期)光合作用、膜脂过氧化以及抗氧化系统的影响.结果表明,在150nmol·mol-1O3浓度范围内,随着O3浓度的升高和熏气时间的增加,冬小麦叶片总叶绿素、叶绿素a和b含量总体降低,但孕穗和扬花期T1处理组总叶绿素和叶绿素a含量较CK组有所升高;气孔导度(Gs)开放受到影响,单位叶片面积活性降低,胞间CO2浓度(ci)和气孔限制值(Ls)呈波动变化.同时,冬小麦启动了自我保护机制,具体表现为SOD(超氧化物歧化酶)活性先快速升高而后逐渐下降,POD(过氧化物酶)活性呈先下降而后快速升高的变化趋势;从拔节期到扬花期以及从灌浆期1到灌浆期2,CAT(过氧化氢酶)活性表现为先快速升高而后"相对降低",MDA(丙二醛)含量则持续升高;类胡萝卜素含量先升高后下降,单位叶片面积热耗散增加.结果表明,抗氧化酶并不能完全消除冬小麦体内过多的活性氧,造成活性氧积累,进一步加剧了膜脂过氧化作用,导致膜透性增加,叶绿素降解,净光合速率降低,加速冬小麦叶片的老化.

Effects of Ozone Stress upon Winter Wheat Photosynthesis,Lipid Peroxidation and Antioxidant Systems

Stress effects of surface increased ozone concentration on winter wheat photosynthesis,lipid peroxidation and antioxidant systems in varied growth stages (jointing stage,booting stage,blooming stage and grain filling stage) were studied,the winter wheat was exposed to open top chambers (OTCs) in an open field conditions to three levels ozone concentrations (CK,100 nmol·mol^-1,150 nmol·mol^-1).The results revealed that within 150 nmol·mol^-1 ozone concentration,as the ozone concentration and time increased,total chlorophyll content,chlorophyll a and b contents of winter wheat leaves were general declined,but compared to CK,the total chlorophyll and chlorophyll a content of T1 treatment groups were a little higher at booting and blooming stage; the conductance of stomatal was affected,the activation of unit leaf area decreased,intercellular CO₂ concentration and stomatal limitation value showed a fluctuation change tendency.At the same time,a self-protective mechanism of winter wheat were launched.Concrete expression of SOD activity first increased rapidly and then gradually decreased,the activity of POD showed a decrease firstly and then rapidly increased. From the jointing stage to the blooming stage and from the grain filling stage one to grain filling stage two,the activity of CAT rapidly increased first and then comparatively decreased,but the content of MDA kept steadily rising.The carotenoid content increased first and then decreased,heat dissipation of unit leaf area increased.These results indicate that antioxidant enzymes can not completely eliminate excessive reactive oxygen species in vivo of winter wheat,then lead to accumulation of reactive oxygen species,further exacerbate the lipid peroxidation,that result in the increase of membrane permeability,degradation of chlorophyll,reduction of net photosynthetic rate,imposing on the winter wheat leaves senescence process.