荫蔽信号对大豆幼苗生长和光合特性的影响

红光/远红光比值(R/FR)下降是自然界荫蔽发生的重要信号。为探究大豆幼苗对荫蔽信号的应答机制,本文采用室内盆栽试验,以‘南豆12’和‘南032-4’两个大豆品种幼苗为材料,通过正常光照和低R/FR两种光照处理后,对其形态、光合特性以及叶绿素荧光参数进行研究。结果表明:与正常光照相比,低R/FR下,两个大豆材料幼苗均表现出典型的避荫性反应,即株高、叶面积、叶柄长、节间长增加,茎秆变细,其中,‘南豆12’的株高、叶柄长、节间长分别显著增加7.86%、81.48%、26.55%,‘南032-4’分别增加3.95%、76.67%、20.00%;叶片的光合速率(Pn)、蒸腾速率(Tr)、气孔导度(Gs)提高,胞间二氧化碳浓度(Ci)和初始荧光强度(Fo)、最大荧光(Fm)、最大光化学效率(Fv/Fm)、PSⅡ实际光化学效率(ΦPSⅡ)、光化学淬灭系数(q P)等降低,非光化学淬灭系数(q N)升高,总干物质积累量增加,其中,‘南豆12’和‘南032-4’的Pn分别增加37.21%和39.04%、总干物质积累量分别增加12.35%和17.36%、Ci分别降低9.29%和11.72%。然而,不同大豆材料对低R/FR的敏感程度不同。在低R/FR光环境下,‘南豆12’较‘南032-4’表现出较低的株高、节间长、叶柄长,较大的叶面积和茎粗,较高的光能传递转换效率、Pn、Gs以及干物质积累量,体现了对荫蔽较强的适应性。本研究进一步证实了大豆具有感受荫蔽信号(低R/FR)的能力,但其敏感程度因品种不同而不同,在间套作过程中,为提高大豆耐荫性,降低大豆因避荫反应导致的倒伏率,保障大豆产量,应该选择对荫蔽信号不敏感的品种。

Effect of shading signal on growth and photosynthetic characteristics of soybean seedlings

Thereductionintheratioofredlight(R)tofar-redlight(FR)isanimportantsignalofshadestressinnature.TheobjectiveofthisstudywastoinvestigatetheresponsemechanismofsoybeanseedlingstolowR/FRsignals.Tothisend,apotcultureexperimentwasconductedtostudytheeffectofnormalandlowR/FRlightirradiationonthemorphology,photosyntheticcharacteristics and chlorophyll fluorescence of two soybean varieties (Glycine max L.) seedlings — ‘Nandou12 ‘and‘Nan032-4’.Theresultsindicatedthatcomparedwithseedlingsundernormallight,low-R/FRlightincreasedsoybeanplantheight,leafarea,petiolelengthandinternodelength,butreducedstemdiameter.Plantheight,petiolelengthandinternodelength of ‘Nandou12’ increased by 7.86%, 81.48% and 26.55%, and that of ‘Nan032-4’ increased by 3.95%, 76.67% and20.00%,respectively,comparedwiththecorrespondingnormallighttreatment.Alsocomparedwithseedlingsundernormallight,leafphotosyntheticrate(Pn),transpirationrate(Tr),stomatalconductance(Gs)andphotochemicalquenchingcoefficient(qN) of seedlings under low R/FR treatment increased. However, intercellular CO2concentration (Ci), initial fluorescenceintensity (Fo), maximum fluorescence (Fm), maximum photochemical efficiency (Fv/Fm), actual PS Ⅱ  photochemicalefficiency(ΦPSⅡ)andlightchemicalquenchingcoefficient(qP)decreasedunderlowR/FRtreatment.Meanwhile,low-R/FRincreaseddrymatteraccumulation.UnderlowR/FRtreatment,Pnanddrymatteraccumulationof‘Nandou12’increasedby37.21%and12.35%andthoseof‘Nan032-4’increasedby39.04%and17.36%,respectively.Comparedwithseedlingsundernormallighttreatment,Ciof‘Nandou12’and‘Nan032-4’decreasedby9.29%and11.72%,respectively.However,differentsoybeanvarietieshaddifferentdegreesofresponsetolow-R/FR.Underlow-R/FRlightcondition,theplantheight,internodelengthandpetiolelengthof‘Nandou12’werelowerthanthoseof‘Nan032-4’,however,theleafarea,stemdiameter,lightenergyconversionefficiency,photosyntheticrate(Pn),stomatalconductance(Gs)anddrymatteraccumulationof‘Nandou12’seedlings were higher than those of ‘Nan032-4’. This indicated that ‘Nandou12’ variety had stronger shade tolerance than‘Nan032-4’variety.Furthermore,thisstudyconfirmedthatsoybeanwassufficientlysensitivetolow-R/FRshadingsignal,butdifferentvarietieshaddifferentsensitivities.Therefore,inintercroppingsystems,itwasrecommendedtouseshade-tolerantsoybeanvarietiestoreducelodgingandincreasesoybeanyield.