Low-Nitrogen Stress Stimulates Lateral Root Initiation and Nitrogen Assimilation in Wheat: Roles of Phytohormone Signaling

• Published in: Journal of plant growth regulation 2021-02, Vol.40 (1), p.436-450
• Main Authors: Lv, Xuemei, Zhang, Yunxiu, Hu, Ling, Zhang, Yan, Zhang, Bin, Xia, Haiyong, Du, Wanying, Fan, Shoujin, Kong, Lingan
• Format: Article
• Language: English
• Subjects: Acetic acid; Adenosine triphosphatase; Agriculture; Ammonium; Assimilation; Biological assimilation; Biomedical and Life Sciences; Biosynthesis; Crop production; Cytokinins; Efflux; Enzyme-linked immunosorbent assay; Gibberellins; Glutamate-ammonia ligase; Glutamine; H+-transporting ATPase; Hydrogen; Indoleacetic acid; Jasmonic acid; Life Sciences; Nitrate reductase; Nitrates; Nitrogen; Physiological responses; Phytohormones; Plant Anatomy/Development; Plant growth; Plant hormones; Plant Physiology; Plant Sciences; Protein biosynthesis; Reductases; Salicylic acid; Seedlings; Stress; Stress concentration; Wheat
• ISSN: 0721-7595; 1435-8107
• DOI: 10.1007/s00344-020-10112-5

Nitrogen (N) deficiency is one of the factors limiting crop productivity worldwide. As major forms of N, nitrate (NO 3 − ) and ammonium (NH 4 + ) regulate plant growth as signals. Although there are abundant studies on the response of many plants to N stress, the mechanism by which wheat ( Triticum aestivum L.) roots adapt to low N, especially to low-NH 4 + stress, has not been fully elucidated. In this study, wheat seedlings were planted in 1/2-strength Hoagland’s solution containing 5 mM NO 3 − , 0.1 mM NO 3 − , or 0.1 mM NH 4 + to characterize root physiological responses to N deficit. Under low-N stress, root fresh weight, lateral root number increased compared with those under control conditions. Moreover, the concentrations of indole-3-acetic acid (IAA), cytokinins (CKs), gibberellin (GA 3 ), and jasmonic acid (JA) increased, while the salicylic acid (SA) concentration decreased under low-N stress. Assays using enzyme-linked immunosorbent assay (ELISA) and non-invasive micro-test technology (NMT) showed that H + -ATPase activity, the H + efflux, and the IAA influx increased, while N influx decreased under low-N stress. Further study revealed that low-NO 3 − stress increased nitrate reductase and glutamine synthetase activities, while low-NH 4 + stress increased the activities of glutamine synthetase and glutamate synthase. In conclusion, low-N stress altered root IAA, CKs, GA 3 , JA, and SA concentrations; increased H + -ATPase activity and H + efflux; promoted an increase in lateral root number and thus N absorption area. Besides, low-N stress increased the activities of key enzymes related to N assimilation, promoted protein biosynthesis, and ultimately enhanced root growth.