Temperature dependence of nitrate uptake kinetics in Triticum aestivum L. and Triticum dicoccon Schrank cultivars

Temperature is a key parameter that influences the uptake and subsequent utilization of nitrogen by plants. Both suboptimal and supraoptimal temperatures can impair nutrient uptake. The close relatives of bread wheat provide a possible source for breeders to increase stress tolerance. The effect of the increasing temperature (5, 10, 15, 20 and 30 °C) on nitrate uptake and metabolism in five modern spring cultivars of bread wheat (Triticum aestivum L.) and two cultivars of emmer wheat (Triticum dicoccon Schrank), was monitored. Wheat plants were grown under controlled conditions in hydroponics. The parameters of Michaelis-Menten kinetics, maximum uptake rate (Vmax), the Michaelis constant (Km) and selected characteristics of nitrate metabolism, the activity of nitrate reductase (NR) and contents of nitrate in leaves were observed. The effect of temperature was significant for all studied traits except Km, while the cultivar factor was significant for Vmax, Km, NR and root/shoot ratio (R/S). Emmer wheat cultivar Rudico had significantly higher Vmax at 5, 15, 20 and 30 °C than all bread wheat cultivars, on average 7.07, in comparison with 4.09-4.43 μmol NO3-/g FW/h in bread wheat cultivars. Emmer wheat Rudico and Tapiruz had significantly higher Km (on average, 41.59 and 47.22 μM NO3-) than bread wheat cultivars (27.59-33.44 μM NO3-). Differences in the studied kinetic parameters of nitrate uptake offer the possibility of using T. dicoccon genotypes in breeding for better nitrogen use efficiency.