低磷胁迫对不同根型苜蓿光合及叶绿素荧光特性的影响

Effects of low phosphorus stress on photosynthetic and chlorophyll fluorescence characteristics of alfalfa with different root types

为探究不同根型苜蓿播种当年及生长第二年叶片光合及荧光特性对低磷胁迫的响应和适应能力,以根蘖型、直根型、根茎型苜蓿为研究对象,采用盆栽试验研究低磷胁迫对各根型苜蓿光合作用参数、类胡萝卜素含量、叶绿素含量及叶绿素荧光参数的影响。结果表明:低磷胁迫下,不同根型苜蓿的叶绿素a、叶绿素b、类胡萝卜素和叶绿体色素含量、光合、荧光参数均降低,与常磷相比以上各参数降幅分别为2.9%~47.9%、2.1%~47.8%、8.1%~57.8%、2.6%~7.8%、0.5%~60.2%、1.1%~52.0%,表明非气孔因素限制磷胁迫下苜蓿的光合作用,且低磷胁迫下苜蓿植株光反应中心遭到破坏,光合性能减弱。各根型苜蓿的胞间CO_(2)浓度、水分利用效率及非光化学淬灭系数均增加,增幅分别为2.9%~12.2%、10.0%~96.5%和5.7%~27.4%;播种当年及生长第二年根茎型清水紫花苜蓿的叶绿素a、叶绿素b、类胡萝卜素、叶绿体色素含量及净光合速率、气孔导度、气孔限制值受低磷胁迫影响最大,较常磷处理分别下降47.9%、47.8%、57.8%、47.8%、37.5%、22.1%、19.8%和16.6%、24.5%、16.6%、19.0%、35.4%、54.2%、24.2%,直根型和根蘖型苜蓿较根茎型苜蓿表现出更强的耐低磷胁迫能力。相关性分析表明,低磷胁迫下供试苜蓿叶片PSII系统结构及其生理状态受到损伤,且叶绿素大量分解,抑制光合电子传递,使光合作用受阻。

To explore the responses and adaptability of leaf photosynthesis and chlorophyll fluorescence of different root-type alfalfas under low phosphorus stress in the first year and the following year,a pot experiment using three root types of alfalfa of creeping rooted Medicago varia Martin‘Gongnong No.4’,tap rooted M.sativa‘Longdong’,and rhizomatous rooted M.sativa‘Qingshui’as the experimental materials was conducted.The effects of low phosphorus stress on photosynthesis parameters,carotenoid content,chlorophyll content,and chlorophyll fluorescence parameters were studied.The results showed that the chlorophyll a,chlorophyll b,carotenoids and chloroplast pigment content,photosynthetic and fluorescence parameters of alfalfa of different root types were reduced under low phosphorus stress,compared with the normal the decrease rate was between 2.9%~47.9%,2.1%~47.8%,8.1%~57.8%,2.6%~7.8%,0.5%~60.2%,and 1.1%~52.0%,respectively,indicating that non-stomatal factors limited the photosynthesis of alfalfa under phosphorus stress.The photosynthetic performance of alfalfa plants was weakened by the destruction of the photoreaction center of alfalfa plants under low phosphorus stress.The intercellular CO_(2) concentration,water use efficiency and non-photochemical quenching coefficient of alfalfa increased by 2.9%~12.2%,10.0%~96.5%and 5.7%~27.4%,respectively.The chlorophyll a,chlorophyll b,carotenoids,chloroplast pigment contents,net photosynthetic rate,stomatal conductance,and stomatal limitation value of rhizome alfalfa were most affected in the first year and the following year,which decreased by 47.9%,47.8%,57.8%,47.8%,37.5%,22.1%,19.8%,and 16.6%,24.5%,16.6%,19.0%,35.4%,54.2%,24.2%,respectively.From the point of view,tap rooted and creeping rooted alfalfa showed greater resistance to low phosphorus stress than rhizomatous rooted alfalfa.The correlation analysis further showed that the structure and physiological state of PSII system in alfalfa leaves under low phosphorus stress were damaged,and chlorophyll was decomposed in large quantities,which inhibited photosynthetic electron transport and hindered photosynthesis.