金沙江干热河谷新银合欢(Leucaena leucocephala)的光合与荧光特征干湿季对比研究

Comparative study on photosynthetic physiological and chlorophyll fluorescence characteristics of Leucaena leucocephala in wet and dry season,Jinsha river dryhot valley,China

为了研究引进树种对干热河谷环境的适应性,以生长于干热河谷野外环境中的新银合欢(Leucaena leucocephala)为研究对象,研究分析了其在湿季(7月)和干季(11月)的光合生理特征和叶绿素荧光特征。结果表明:(1)在Pn-Ci响应曲线中,当Ci<150μmol/mol,干季的净光合速率(Net photosynthetic rate,Pn)高于湿季,而当Ci>150μmol/mol,干季的Pn低于湿季;(2)相较于湿季,干季的初始羧化效率(Initial carboxylation efficiency,CE)、光合能力(Photosynthetic capacity,Amax)、CO2补偿点(CO2 compensation point,Γ)、光呼吸速率(Photorespiration rate,Rp)、最大羧化速率(Maximum carboxylation rate,Vcmax)、最大电子传递速率(Maximum electron transport rate,Jmax)、磷酸丙糖利用率(Triose phosphates utilization rate,TPU)、Jmax/Vcmax、气孔限制值(Stomatal limitation,Ls)和叶片饱和水汽压差(Vapor pressure deficit,VPD)均显著下降(P<0.05),而暗呼吸速率(Dark respiration rate,Rd)、胞间CO2浓度(Intercellular CO2 concentration,Ci)、气孔导度(Stomatal conductance,Gs)、蒸腾速率(Transpiration rate,Tr)、饱和光下最大净光合速率(Light-saturated net photosynthetic rate,Pnmax)和水分利用效率(Water use efficiency,WUE)则显著上升(P<0.05);(3)干季的PSII实际光化学效率(Actual photochemical efficiency of PSII,ФPSII),光化学猝灭系数(Photochemical fluorescence quenching,qP),电子传递效率(Electron transport rate,ETR)较湿季出现显著下降(P<0.05),非光化学猝灭系数(Non-photochemical fluorescence quenching,NPQ)显著增加(P<0.05);(4)叶绿素荧光参数的ФPSII、NPQ、ETR与各光合生理指标相关性较强。在干热河谷地区,气孔限制是影响新银合欢湿季光合速率的主要因素;而非气孔限制是影响其干季光合速率的主要因素。

Jinsha river dry-hot valley with a fragile ecology in Southwest China is characterized by hot and dry climate and serious vegetation degradation,that is difficult to rehabilitate the original ecosystem structure and functions.In order to study the adaptability of the introduced tree species to environment of Jinsha river dry-hot valley,photosynthetic physiological characteristics and chlorophyll fluorescence characteristics of Leucaena leucocephala were measured in dry season(November)and wet season(July),respectively.The results showed that:(1)According to the Pn-Ci response curves,net photosynthetic rate(Pn)in dry season was higher than that in wet season at Ci<150μmol/mol,but it was lower at Ci>150μmol/mol.(2)Compared with wet season,vapor pressure deficit(VPD),stomatal limitation(Ls),initial carboxylation efficiency(CE),photosynthetic capacity(Amax),CO2 compensation point(Γ),photorespiration rate(Rp),the maximum carboxylation rate(Vcmax),the maximum electron transport rate(Jmax),triose phosphates utilization rate(TPU),Jmax/Vcmax,actual photochemical efficiency of PSII(ФPSII),photochemical fluorescence quenching(qP),and electron transport rate(ETR)of Leucaena leucocephala decreased significantly in dry season(P<0.05).(3)Compared with wet season,intercellular CO2 concentration(Ci),stomatal conductance(Gs),transpiration rate(Tr),water use efficiency(WUE),light-saturated net photosynthetic rate(Pnmax),dark respiration rate(Rd),and non-photochemical fluorescence quenching(NPQ)of Leucaena leucocephala significantly increased in dry season(P<0.05).(4)ФPSII,NPQ and ETR,three indices of chlorophyll fluorescence parameters,well correlated with photosynthetic physiological indices.In conclusion,the main factor influencing the photosynthetic rate of Leucaena leucocephala was the stomatal limitation in wet season,but it was non-stomatal limitation in dry season.