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STUDIES ON PHYSIOLOGICAL MECHANISMS OF NITROGEN USE EFFICIENCY IN SORGHUM
Abstract
Nitrogen efficient plants are potential solutions to low fertility and fertilizer-induced environmental problems. Understanding mechanisms of N use efficiency (NE) is essential in plant improvement. Physiological traits that may be associated with NE were studied. Growth, N uptake, patterns of dry matter (DM) and N allocation, grain yield, and photosynthetic rates (PS) of selected sorghum (Sorghum bicolor (L.) Moench) genotypes were examined. Ratios of DM, grain production, and PS to plant or leaf N (representing NE) of genotypes were also compared. Plants were grown hydroponically (some in solid medium) in a greenhouse (low N) and in an optimum field condition. Genotype relationship changed with N level, growth stage, or environment. Genotype TP24R (efficient) was most responsive to added N (largest regression coefficient for DM production). Generally, higher DM producing genotypes were also high in N uptake, ${\rm NE}\sb1$ (g total DM ${\rm g}\sp{-1}$ total N), NUE (g total DM $\%{\rm N}\sp{-1})$ and PS-NEff2 (umol ${\rm CO}\sb2\ \%{\rm N}\sp{-1}$leaf ${\rm s}\sp{-1}),$ and low in PSratel (umol ${\rm CO\sb2\ m\sp{-2}}$ leaf ${\rm s}\sp{-1}),$ or PS-NEff1 (umol ${\rm CO\sb2\ g\sp{-1}}$ N leaf ${\rm s}\sp{-1})$ in the greenhouse. No definite pattern was noted between the various NE criteria and allocation patterns of DM or N. Leaf N concentration or specific weight largely affected genotype rank for PS-N efficiencies but not for PS. Photosynthetic rates of TP24R (had low leaf N concentration) was low in the greenhouse but was as high as that of inefficient KS19 consist of highest PS in the field. TP24R had greater leaf DM or area and greater computed total PS than the other genotypes. CK60 (intermediate efficient) ranked low in total DM, but had higher grain yield than Martin (intermediate efficient) or KS19. Among genotypes, KS19 was highest in grain allocation (harvest index) and in ${\rm NE}\sb2$ (g grain ${\rm g}\sp{-1}$ total N), despite being lowest in grain or DM yield. Nitrogen use efficiency is expressed in various ways and characters used for its definition are affected by growth stage and environment. Only after NE has been specifically defined and confirmed on more numbers of genotypes, will physiological traits associated with NE become useful as selection criteria, or as tools in the study of mechanism(s).
Subject Area
Agronomy
Recommended Citation
FERNANDEZ, PAMELA G, "STUDIES ON PHYSIOLOGICAL MECHANISMS OF NITROGEN USE EFFICIENCY IN SORGHUM" (1987). ETD collection for University of Nebraska-Lincoln. AAI8719777.
https://digitalcommons.unl.edu/dissertations/AAI8719777