Mechanisms regulating yield determination in supernodulating soybean genotypes

点击翻译按钮获取中文摘要

In this study, we aimed to verify the hypothesis that elevated [CO_2]-induced enhancement of biomass production of soybean is greater in genotypes that have a higher N fixation capacity. Furthermore, we aimed to identify the interactive effects of N fertilization, temperature, and [CO_2] on biomass production. Genetically related genotypes that have different N fixation capaciry: normally-nodulating genotypes, supernodulating genotypes, and non-nodulating genotypes were grown in pots, with or without N fertilizer. They were then subjected to two different [CO_2] (ambient and elevated (ambient + 200 兪mol mol^<-1>)) x two temperature regimes (low, high (low + 4-5 ?C)). Top dry weight at maturity was the greatest in the elevated [CO_2] x high temperature regime, irrespective of genotype and N fertilization, and was greater in nodulating genotypes than in non-nodulating genotypes. The marked enhancement of biomass production of nodulating genotypes was ascribed to higher leaf expansion rate, which appeared to be associated with its superior N fixing activity. However, the difference in [CO_2]-induced biomass enhancement between supernodulating and normally-nodulating genotypes was not significant. Grain yield was not significantly enhanced by elevated [CO_2] when high temperature was imposed. The physiological mechanisms involved in impaired sink formation under elevated [CO_2] x high temperature conditions remain to be clarified.