To study on changes and relationship of soybean photosynthetic gas exchange parameters in different growth stage,2 experiments with 2 soybean varieties and 20 soybean materials were designed.In the first experiment,photosynthetic gas exchange parameters of 2 soybean varieties were measured with Li6400XT on 9 growth stages:VC,V3,V5,R1,R3,R5,R6,R6.5,R7.Chlorophyll contents were measured with SPAD on the same leaves.In the other experiment,20 soybean materials were used to research the relationship of the photosynthetic gas exchange parameters between V3 and V9 growth stage.Results showed that 2 soybean varieties photosynthetic capacity was more higher from V3 to R6.And that was the highest on R5 and R6 growth stage.Chlorophyll content showed the same trend.Pn,Gs,Tr and SPAD was decreased rapidly after R6 growth stage.Pn,Gs and WUE in V3 growth stage was unrelated to that of V9 growth stage.Tr and Ci of V3 growth stage was significantly related to that of V9 growth stage (r =0.518,P =0.007 and r =0.523,P =0.018).And Pn of the V3 and V9 growth stages was unrelated to the soybean yield.Data multiplied by Pn of V3 and V9 growth stages and days of soybean whole growth period was related to yield significantly (r =0.561,r =0.612).Pt (data multiplied by average Pn value of those 2 growth stages and days of soybean whole growth period) was significantly rclated to yield (r =0.676).%为了对大豆全生育期光合特性进行系统研究,选用两个早期光合速率差异较大的大豆品种,测定真叶期(vC),三节期(v3)、五节期(v5)、始花期(R1)、初荚期(R3)、始粒期(R5)、鼓粒盛期(R6)、鼓粒盛期至始熟期中期(R6.5)、始熟期(R7)等9个生长时期大豆光合气体交换参数(光合速率Pn、气孔导度Gs、胞间CO2浓度Ci、蒸腾速率Tr和叶绿素含量等,测定了20份大豆材料V3和V9两个生育时期大豆光合气体交换参数,分析不同材料光合气体交换参数间变化关系.结果表明,在整个生育过程中,大豆于V3～ R6时期间保持较高光合能力,且R6和R5期Pn值最高,SPAD值最大.R6期之后大豆Pn、Gs、Tr、SPAD迅速下降.20份大豆材料V3和V9期的Pn和Tr无显著相关性;Gs和Ci显著相关,相关系数分别为0.583和0.523.大豆产量同V3和V9期Pn值相关性均不显著,但同两个生育时期Pn值与全生育期乘积值显著相关,相关系数分别为0.561、0.612;同两生育时期Pn值均值与全生育期乘积(Pt)也呈显著正相关,相关系数为0.676.
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