Tang Hongliang, Niu Le, Wei Jing, Chen Xinying, Chen Yinglong
College of Life Science, Hebei University, Baoding, China.
State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau, Northwest A&F University, Yangling, China.
Front Plant Sci. 2019 Jul 3;10:856. doi: 10.3389/fpls.2019.00856. eCollection 2019.
Low phosphorus (P) availability and salt stress are two major constraints for maize ( L.) growth in north China. A combination of salinity and high P rather than low P is more detrimental to the growth of maize. However, little is known about the mechanisms by which P nutrition modifies the salt tolerance and P uptake of maize. The present study aimed to investigate the combined effects of salinity and P on maize growth and P uptake, and to address the physiological mechanisms of salt tolerance influenced by P availability in maize. Seedlings of a local maize cultivar XY335 were grown hydroponically for 35 days under low (5 μM) or sufficient P supply (200 μM) with or without 100 mM NaCl. Root morphological traits, tissue mass density, leaf osmolytes (sugars and proline) accumulation, and Na/K ratio were measured to allow evaluation of the combined effects of salinity and P on maize growth and P uptake. Both P deficiency and salinity markedly reduced the growth of maize. However, P deficiency had a more pronounced effect on shoot growth while salinity affected root growth more prominently. Combined effects of P deficiency and salinity on total root length, root surface area, and average root diameter were similar to that of plants grown under salt stress. The combination of P deficiency and salinity treatments had a more pronounced effect on tissue mass density, leaf proline and soluble sugars compared to individual treatment of either low P or NaCl. When exposed to salt stress, maize plants of sufficient P accumulated greater amount of Na than those under P deficit, but similar amounts of K were observed between the two P treatments. Salt stress significantly increased shoot P concentration of maize with sufficient P ( < 0.01), but not for P-deficient plants. In sum, shoots and roots of maize exhibited different responses to P deficiency and salinity, with more marked effect of P deficiency on shoots and of salinity on roots. P deficiency improved salt tolerance of maize plants, which was associated with the increase of tissue mass density, accumulation of osmolytes, reduction of Na accumulation, and selective absorption of K over Na.
低磷有效性和盐胁迫是华北地区玉米生长的两大主要限制因素。盐分和高磷组合而非低磷对玉米生长更为有害。然而，关于磷营养调节玉米耐盐性和磷吸收的机制知之甚少。本研究旨在探究盐分和磷对玉米生长及磷吸收的综合影响，并探讨磷有效性影响玉米耐盐性的生理机制。当地玉米品种XY335的幼苗在低磷（5 μM）或充足磷供应（200 μM）条件下，分别在添加或不添加100 mM NaCl的情况下水培35天。测量根系形态特征、组织质量密度、叶片渗透物质（糖和脯氨酸）积累以及钠/钾比，以评估盐分和磷对玉米生长及磷吸收的综合影响。缺磷和盐胁迫均显著降低了玉米的生长。然而，缺磷对地上部生长的影响更为显著，而盐胁迫对根系生长的影响更为突出。缺磷和盐胁迫对总根长、根表面积和平均根直径的综合影响与盐胁迫下生长的植株相似。与单独的低磷或NaCl处理相比，缺磷和盐胁迫处理组合对组织质量密度、叶片脯氨酸和可溶性糖的影响更为显著。当暴露于盐胁迫时，充足磷供应的玉米植株积累的钠比缺磷植株多，但两种磷处理下的钾积累量相似。盐胁迫显著增加了充足磷供应的玉米地上部磷浓度（P < 0.01），但缺磷植株则未增加。总之，玉米的地上部和根系对缺磷和盐胁迫表现出不同的响应，缺磷对地上部的影响更为显著，盐胁迫对根系的影响更为显著。缺磷提高了玉米植株的耐盐性，这与组织质量密度的增加、渗透物质的积累、钠积累的减少以及钾对钠的选择性吸收有关。
