Zhu Yunna, Qi Baifu, Hao Yanwei, Liu Houcheng, Sun Guangwen, Chen Riyuan, Song Shiwei
College of Horticulture, South China Agricultural University, Guangzhou, China.
Henry Fok College of Biology and Agriculture, Shaoguan University, Shaoguan, China.
Front Plant Sci. 2021 Apr 30;12:656144. doi: 10.3389/fpls.2021.656144. eCollection 2021.
Compared with sole nitrogen (N), the nutrition mixture of ammonium (NH ) and nitrate (NO ) is known to better improve crop yield and quality. However, the mechanism underlying this improvement remains unclear. In the present study, we analyzed the changes in nutrient solution composition, content of different N forms in plant tissues and exudates, and expression of plasma membrane (PM) H-ATPase genes () under different NH /NO ratios (0/100, 10/90, 25/75, 50/50 as control, T1, T2, and T3) in flowering Chinese cabbage. We observed that compared with the control, T1 and T2 increased the economical yield of flowering Chinese cabbage by 1.26- and 1.54-fold, respectively, whereas T3 significantly reduced plant yield. Compared with the control, T1-T3 significantly reduced the NO content and increased the NH , amino acid, and soluble protein contents of flowering Chinese cabbage to varying extents. T2 significantly increased the N use efficiency (NUE), whereas T3 significantly decreased it to only being 70.25% of that of the control. Owing to the difference in N absorption and utilization among seedlings, the pH value of the nutrient solution differed under different NH /NO ratios. At harvest, the pH value of T2 was 5.8; in the control and T1, it was approximately 8.0, and in T3 it was only 3.6. We speculated that appropriate NH /NO ratios may improve N absorption and assimilation and thus promote the growth of flowering Chinese cabbage, owing to the suitable pH value. On the contrary, addition of excessive NH may induce rhizosphere acidification and ammonia toxicity, causing plant growth inhibition. We further analyzed the transcription of PM H-ATPase genes (). and transcription in roots was significantly down-regulated by the addition of the mixture of NH and NO , whereas the transcription of , in roots and , , and in leaves was sharply up-regulated by the addition of the mixture; the transcription of was mainly enhanced by the highest ratio of NH /NO . Our results provide valuable information about the effects of treatments with different NH /NO ratios on plant growth and N uptake and utilization.
与单一氮素（N）相比，铵态氮（NH₄⁺）和硝态氮（NO₃⁻）的营养混合物能更好地提高作物产量和品质，这是已知的。然而，这种改善背后的机制仍不清楚。在本研究中，我们分析了不同NH₄⁺/NO₃⁻比例（0/100、10/90、25/75、50/50作为对照，分别为T1、T2和T3）下，花椰菜营养液成分的变化、植物组织和渗出物中不同氮形态的含量以及质膜（PM）H⁺-ATPase基因（）的表达。我们观察到，与对照相比，T1和T2分别使花椰菜的经济产量提高了1.26倍和1.54倍，而T3显著降低了植株产量。与对照相比，T1-T3不同程度地显著降低了花椰菜的NO₃⁻含量，提高了NH₄⁺、氨基酸和可溶性蛋白的含量。T2显著提高了氮素利用效率（NUE），而T3显著降低，仅为对照的70.25%。由于幼苗对氮的吸收和利用存在差异，不同NH₄⁺/NO₃⁻比例下营养液的pH值也不同。收获时，T2的pH值为5.8；对照和T1中约为8.0，T3中仅为3.6。我们推测，合适的NH₄⁺/NO₃⁻比例可能由于适宜的pH值而改善氮的吸收和同化，从而促进花椰菜的生长。相反，过量添加NH₄⁺可能会诱导根际酸化和氨毒害，导致植物生长受抑制。我们进一步分析了PM H⁺-ATPase基因（）的转录情况。添加NH₄⁺和NO₃⁻混合物后，根系中 和 的转录显著下调，而添加该混合物后，根系中 、 以及叶片中 、 、 的转录急剧上调； 的转录主要在最高NH₄⁺/NO₃⁻比例时增强。我们的结果为不同NH₄⁺/NO₃⁻比例处理对植物生长及氮吸收和利用的影响提供了有价值的信息。
