增硝营养对水稻不同生育时期生长及氮素吸收同化的影响

The effect of nitrate （NO3^-） on rice （Oryza sativa L.） growth as well as N absorption and assimilation during different growth stages was examined using three typical rice cultivars. Dry weight, yield, N uptake, nitrate reductase activity （NRA） in leaves, and glutamine synthetase activity （GSA） in roots and leaves during their entire growth periods, as well as the kinetic parameters of ammonium （NH4^＋） uptake at the seedling stage, were measured with solution culture experiments. Results indicated that addition of NH4^＋-N and NO3^-N at a ratio of 75：25 （NH4^＋＋NO3^- treatment） when compared with that of NH4^＋-N alone （NH4^＋ treatment） increased the dry weight of ‘Nanguang＇ cultivar by 30% and ‘Yunjing 38＇ cultivar by 31%, and also increased their grain yield by 21% and 17%, respectively. For the four growth stages, the total N accumulation in plants increased by an average of 36% for ‘Nanguang＇ and 31% for ‘Yunjing 38＇, whereas the increasing effect of NO3^- in the ‘4007＇ cultivar was only found at the seedling stage, in the NH4^＋＋NO3^- treatment compared to the NH4^＋ treatment, NRA in the leaves increased by 2.09 folds, and GSA increased by 92% in the roots and 52% in the leaves of the three cultivars. NO3^- supply increased the maximum uptake rate （Vmax） in the ‘Nanguang＇ and ‘Yunjing 38＇ cultivars, reflecting that the NO3^- itself, not the increasing N concentration, increased the uptake rate of NH4^＋ by rice. There was no effect on the apparent Michaelis-Menten constant （Kin） of the three cultivars. Thus, some replacement of NH4^＋ with NO3^-could greatly improve the growth of rice plants, mainly on account of the increased uptake of NH4^＋ promoted by NO3^-, and future studies should focus on the molecular mechanism of the increased uptake of NH4^＋ by NO3^-.

Nitrate effect on rice growth and nitrogen absorption and assimilation at different growth stages

The effect of nitrate (NO^?₃) on rice (Oryza sativa L.) growth as well as N absorption and assimilation during different growth stages was examined using three typical rice cultivars. Dry weight, yield, N uptake, nitrate reductase activity (NRA) in leaves, and glutamine synthetase activity (GSA) in roots and leaves during their entire growth periods, as well as the kinetic parameters of ammonium (NH⁺₄) uptake at the seedling stage, were measured with solution culture experiments. Results indicated that addition of NH⁺₄-N and NO^?₃-N at a ratio of 75:25 (NH⁺₄+NO^?₃ treatment) when compared with that of NH⁺₄-N alone (NH⁺₄ treatment) increased the dry weight of ‘Nanguang’ cultivar by 30% and ‘Yunjing 38’ cultivar by 31%, and also increased their grain yield by 21% and 17%, respectively. For the four growth stages, the total N accumulation in plants increased by an average of 36% for ‘Nanguang’ and 31% for ‘Yunjing 38’, whereas the increasing effect of NO^?₃ in the ‘4007’ cultivar was only found at the seedling stage. In the NH⁺₄+NO^?₃ treatment compared to the NH⁺₄ treatment, NRA in the leaves increased by 2.09 folds, and GSA increased by 92% in the roots and 52% in the leaves of the three cultivars. NO^?₃ supply increased the maximum uptake rate (V_max) in the ‘Nanguang’ and ‘Yunjing 38’ cultivars, reflecting that the NO^?₃ itself, not the increasing N concentration, increased the uptake rate of NH⁺₄ by rice. There was no effect on the apparent Michaelis-Menten constant (K_m) of the three cultivars. Thus, some replacement of NH⁺₄ with NO^?₃ could greatly improve the growth of rice plants, mainly on account of the increased uptake of NH⁺₄ promoted by NO^?₃, and future studies should focus on the molecular mechanism of the increased uptake of NH⁺₄ by NO^?₃.