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Assesment of sorghum response to nitrogen availability

Abstract : Seven accessions of Sorghum bicolor were grown with low (N⁻) and optimal (N⁺) nitrate supply. Growth parameters (plant height and leaf numbers), physiological parameters (nitrate, protein, total N and total C contents) and the activity of glutamine synthetase (GS) were studied in leaves and roots of sorghum plants at three time points of early vegetative growth (2, 4 and, 6 weeks post emergence). Plant height and leaf number were higher with nitrate supply. Except for carbon, all studied parameters were sensitive to N availability and values were typically lower when nitrate supply was low. However, different genotypes displayed considerable variation in their response to N regimes. Variation among genotypes during early vegetative development was observed for plant height, but not for leaf number. Likewise, physiological parameters varied among accessions. A significant and strong correlation, N- and accession-dependent, was detected between plant height and nitrate content. Moreover, nitrate content and GS activity at early growth stages appeared to be good markers to discriminate between nitrate uptake and assimilation capacities of different accessions under both N conditions. In some sorghum accessions, protein and total N content were indicative of high nitrate reduction and assimilation even under N limitation. Chlorophyll content was also sensitive to N availability. Furthermore, expression studies of SbNRT1.1gene copies in leaves and roots of two accessions reflected variability in expression dependent on nitrogen condition, plant organ, plant age, and gene of interest. This study is helpful to characterize different aspects of the N metabolism in sorghum and may aid in the identification of sorghum genotypes with enhanced nitrogen use efficiency, a trait that is of key interest in one of the most important crop plants in arid and semi-arid regions.
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Fatima Awada. Assesment of sorghum response to nitrogen availability. Vegetal Biology. Université Paris Saclay (COmUE), 2016. English. ⟨NNT : 2016SACLS312⟩. ⟨tel-01599245⟩

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