γ-氨基丁酸对高温胁迫下黑麦草光合特性及碳水化合物代谢的影响

Effect of γ-aminobutyric acid on photosynthetic characteristics and carbohydrate metabolism under high temperature stress in perennial ryegrass

以热敏感品种顶峰(Pinnacle)为试验材料,研究了热胁迫下(35℃/30℃,昼/夜)施用外源γ-氨基丁酸(GABA)对黑麦草生长、光合及叶绿素荧光特性、碳水化合物含量及其代谢关键酶基因表达的影响。结果表明,热胁迫造成黑麦草生长减弱,膜透性增加,光合色素含量下降,光合能力和碳水化合物含量显著降低,糖代谢关键酶(蔗糖合成酶、蔗糖磷酸合成酶和转化酶)基因在短时间内(5d)表达显著上调,随后下降;外源施用GABA显著缓解了高温对黑麦草生长的抑制作用,提高了高温胁迫下光合色素和碳水化合物含量,净光合速率(Pn)、气孔导率(Gs)、蒸腾速率(Tr)、CO2羧化效率(CE)、最大光合速率(Amax)和光化学效率(Fv/Fm)、Rubisco最大羧化速率(Vcmax)和RuBP再生速率(Jmax)、光化学猝灭系数(qP)、电子传递速率(ETR)和PSⅡ实际光化学效率(ΦPSⅡ)显著升高,而气孔限制值(Ls)、CO2补偿点(CP)和非光化学猝灭系数(NPQ)显著降低。施用外源GABA降低了高温胁迫下叶片气孔和非气孔限制值,缓解了高温对叶片PSⅡ反应中心的抑制,增强了糖代谢关键酶基因表达的水平,提高了碳水化合物含量,因此有效的提高了黑麦草的耐高温能力。

The aim of this research was to elucidate the effects of exogenousγ-aminobutyric acid(GABA)on high temperature stress metabolism,plant growth,photosynthetic and chlorophyll fluorescence characteristics,carbohydrate content and gene expression levels of key enzymes associated with sugar metabolism.The material studied was a heat sensitive cultivar(Pinnacle)of perennial ryegrass(Lolium perenne)under high temperatures(35/30℃light/dark)in growth chambers for 15 d.It was found that heat stress inhibited plant growth,increased leaf electrolyte leakage and decreased carbohydrate and chlorophyll content,photosynthesis rate.The gene expression levels of key enzymes associated with sugar metabolism were initially up-regulated and subsequently decreased under heat stress.Exogenously applied GABA significantly alleviated the damage effect of heat stress on plant growth and enhanced the chlorophyll content and carbohydrate content under high temperature.The leaf net photosynthetic rate(Pn),stomatal conductance(Gs),transpiration rate(T r),carboxylation efficiency(CE),maximum assimilation(A max),photochemical efficiency(Fv/Fm),maximum velocity of carboxylation(Vc max),maximum electron transfer rate(J max),photochemical quenching(qP),electron transport rate(ETR)and actual photochemical efficiency of PSII(ΦPSⅡ)significantly increased while leaf stomatal limitation(Ls),compensation point(CP)and none photochemical quenching(NPQ)significantly decreased after application of GABA under heat stress.To summarize,exogenous application of GABA reduced leaf stomatal and non-stomatal limitations to photosynthesis and alleviated the inhibition of PSII reaction centers,leading to an enhancement in light and dark reactions of photosynthesis and in photosynthetic potential.Expression levels of key genes for sugar metabolism were also enhanced.These physiological changes acted cumulatively to confer a higher tolerance to heat stress in perennial ryegrass.