Varietal differences in root growth as related to nitrogen uptake by sorghum plants in low-nitrogen environmentTNakamuraauthorJ JAdu-GyamfiauthorAYamamotoauthorSIshikawaauthorHNakanoauthorOItoauthorHybrid (Sorghum bicolor (L.) Moench cv. CSH 9) and local variety (S. bicolor cv. FSRP) of sorghum were grown in an Alfisol field and in pots of Alfisol in semi-arid tropical India, and the productivity of sorghum in low N condition was studied in relation to N absorption by plant. The grain yield of the hybrid (CSH 9) was higher than that of the local variety (FSRP) irrespective of the rate of N application. The reduction in hybrid grain yield was less than that for the local variety when N was not applied. After booting stage hybrid absorbed more N than the local variety. To estimate the role of roots in N absorption, the characteristics of N absorption were parameterized. Relative growth rate was highly correlated with relative N absorption rate in plant. N absorption was regulated by root activity (specific N absorption rate per unit root mass and length). Specific N absorption rate in roots at physiological maturity was higher in the hybrid than in local variety in low N conditions. Therefore, the smaller reduction of hybrid yield in low-N conditions was ascribed to high-N absorption rate in its roots, and the high ability of roots to absorb N after booting stage.Sorghum2002KluwerArticle