套作弱光胁迫对大豆苗期根系形态和生理活性的影响

研究玉米-大豆带状套作弱光环境下大豆苗期根系形态特征、生理特性和生物量积累,明晰苗期大豆根系对套作荫蔽的响应规律,筛选适宜玉米-大豆带状套作的大豆品种,为改良大豆对荫蔽胁迫的适应能力提供理论依据。以NTS1007、桂夏3号和南豆12等3个根系特征不同的大豆品种(系)为试验材料,在盆栽试验条件下,采用挖掘法考察根系形态特征,并对根系活力、表面积、伤流量和生物量积累等指标进行测定和分析。结果表明,与单作相比,玉豆带状套作下大豆主根长和侧根长均显著下降,侧根下降81.8%,主根下降42.8%,侧根下降更为明显;根系可溶性糖含量显著下降,导致根系活力降低,伤流量减少;大豆根系表面积和活跃吸收表面积显著减小,降幅均与一级侧根总长度的降幅呈极显著正相关;大豆植株生物量显著下降,其中地下部下降55.2%,地上部下降37.9%,根冠比减小。不同品种(系)大豆根系对套作的响应程度不同,南豆12的主根长、一级侧根长、根体积降幅最小(33.9%、74.4%、65.3%);桂夏3号的根系表面积和生物量降幅最大(67.1%、48.3%);NTS1007则根冠比、根系活力和伤流量冠比降幅最大(35.4%、39.2%、38.9%)。套作遮荫条件下大豆根系的伸长生长比根系生理性状更能够准确地反映植株根系生长状况,根系长度可作为判定对荫蔽胁迫适应能力的一个重要指标。南豆12在玉米-大豆套作下能够更为合理地分配同化产物,减小荫蔽胁迫对根系形态建成和生理活性的抑制作用,保证根系生物量积累。

Response of roots morphology and physiology to shading in maize-soybean relay strip intercropping system

 Root morphology characteristics, physiological activity and biomass accumulation were studied to investigate the root response to shading under relay-intercropping system in seedling stage. 3 varieties with different root characteristics, NTS1007, GX-3 and ND12 were used in the pod experiment to investigate root activity, root surface area （RSA）, root active absorption area （RAAA）, bleeding sap and biomass accumulation. Compared with the monoculture, the results showed that the length of main root and lateral root decreased significantly in the relay strip intercropping system, and the increase in lateral root （81.8%） was more obvious than that of main root （42.8%）. The soluble sugar content, root activity, bleeding sap, root surface area, and root active absorption area all decreased significantly. The decreasing amplitude of root surface and active absorption area were linearly correlated with the first lateral root length. Biomass decreased and the decrease in the root biomass （55.2%） was more apparent than shoot （37.9%）. Among the 3 varieties, ND12 had the least decrease in main root length, first lateral root length and root volume （33.9%, 74.4%, 65.3%）, but GX-3 had the most significant decrease in RSA and biomass （67.1%, 48.3%） in the relay strip intercropping system, and NTS had the greatest decreasing aptitude in R/S, root activity and bleeding sap/shoot dry matter （35.4%,39.2%,38.9%）. In a relay strip intercropping system, the elongation growth of the soybean root can reflect the status of the root growth more accurately in comparison to monoculture, which can be used as an important indicator of shade-tolerance. ND12 had a rational allocation of assimilation to alleviate the negative effect on morphogenesis and physiological characteristics.