荫蔽锻炼对大豆苗期光合特性的影响

Effect of shade priming on photosynthetic characteristics of soybean seedlings

荫蔽是影响间套作大豆产量进一步提高的限制因素。为探究荫蔽锻炼对大豆叶片光合、荧光特性的影响,本研究采用盆栽试验,分别用远红光LED灯(λ=730nm)、30%透光率遮阳网模拟荫蔽信号和荫蔽胁迫,分锻炼(S1)–恢复(S2)–胁迫(S3)3个阶段,以全过程自然光照为对照(LLLL),设荫蔽信号锻炼(LFLS)、荫蔽胁迫锻炼(LSLS)、不锻炼(LLLS) 3个处理,分析其S3阶段遭受荫蔽胁迫时叶片光合色素含量、光合参数以及叶绿素荧光参数的响应特征。结果表明, LFLS和LSLS较LLLS老叶和成熟叶叶绿素a、叶绿素b、类胡萝卜素含量以及叶绿素总含量显著增加,老叶和新叶叶绿素a/b显著下降。除LSLS成熟叶外,各叶位净光合速率、气孔导度均较未锻炼处理显著增加,老叶和成熟叶锻炼与未锻炼处理胞间二氧化碳浓度差异不显著。与对照相比,无论锻炼与否,后期荫蔽使Fo、qp、NPQ、ΦPSII、ETR降低,而F_v/F_m和F_v'/F_m'则升高,其中,S1阶段的锻炼处理较未锻炼处理Fo下降的幅度更小;老叶qp较对照降低幅度依次为LFLS>LLLS>LSLS,成熟叶为LSLS<LFLS<LLLS,新叶为LSLS>LFLS>LLLS;ΦPSII、ETR均较对照降低但处理间差异不显著; LLLS、LFLS、LSLS新叶中F_v'/F_m'则分别比对照增加6.51%、8.79%和12.05%(P<0.05),锻炼后增加幅度更大。由此可见,通过荫蔽锻炼,大豆能通过光合特征的可塑性来适应光环境并表现出更强的荫蔽耐受能力。

Shade stress limits the further increase of soybean yield in intercropping.In order to investigate the effect of shade priming on photosynthetic and chlorophyll fluorescence characteristics of soybean seedlings,the growth of plants were undergone three stages of shade priming(S1),light recovery(S2),and shade stress(S3).The shade priming included shade signal(increasing the ration of far red with LED lamp of730nm)and shade stress.The treatments of the experiment were natural light(LLLL),shade-signal priming(LFLS),shade-stress priming(LSLS),and no priming(LLLS).The results showed that compared with LLLS,shade priming enhanced chlorophyll a,chlorophyll b,carotenoid contents and total chlorophyll content in old and middle-age leaves significantly,while reduced chlorophyll a/b in old and young leaves.Except for the middle-age leaves of LSLS,both the net photosynthetic rate and stomatal conductance of each leaf position of LFLS and LSLS were significantly increased.And there was no significant difference in intercellular carbon dioxide concentration in old and middle-age leaves between the primed plants and the non-primed plants.Compared with the control(LLLL),Fo,qp,NPQ,ΦPSII,ETR decreased,while Fv/Fm and Fv'/Fm'increased.Among them,the reduction of Fo in the primed was smaller than that in the control.The trend of the reduction of qp was LFLS>LLLS>LSLS in old leaves,while LSLS<LFLS<LLLS in middle-age leaves and LSLS>LFLS>LLLS in young leaves.ΦPSII,ETR considerably decreased as compared with the control,but there was no significant difference between the primed plants and the non-primed plants.Compared with LLLL,the increase of Fv'/Fm'in young leaves of the primed plants was greater than that of the non-primed plants,with the increase of6.51%,8.79%,and12.05%(P<0.05)in LLLS,LFLS,and LSLS,respectively.Therefore,by shade priming at S1,soybeans adapted to the light environment through the plasticity of photosynthetic characteristics and exhibited a stronger tolerance to shade stress occurring during S3.