Exogenous Pi supplementation improved the salt tolerance of maize (Zea mays L.) by promoting Na+ exclusion

Yanling Sun,Shouping Lu,Chunhua Mu,Xia Liu,Hua Zhang,Hongxia Zheng,Xuecai Zhang

doi:10.1038/s41598-018-34320-y

Abstract

The mechanism of phosphate (Pi)-mediated salt tolerance in maize is poorly understood. In this study, the effects of Pi (H2PO4−) on the salt tolerance of two contrasting genotypes was investigated in a pot experiment. We discovered that the application of 3 mM Pi could alleviate salt injury caused by 200 mM NaCl. High amounts of compatible solutes and low amounts of reactive oxygen species (ROS) were also observed under Pi application. Consistent with the increased tolerance, the total number of roots and the growth of shoots increased to relieve salt stress. This phenomenon could be associated with the observed increased expression of nitrate transporters. Furthermore, the seedlings presented a negative relationship between sodium (Na+) and Pi (low Na+ content and high Pi content), which is related to the genes ZmNHX1, ZmPHT1;8, and ZmPHT1;9, indicating that the exclusion of Na+ was promoted by high Pi uptake. However, high Na+ and low potassium (K+) efflux were detected in the roots, and these were positively correlated with two K+ transporters. These observations indicate that Na+ exclusion was directly induced by high K+ retention rather than Pi absorption. We conclude that maize salt tolerance increased in response to Pi application by promoting Na+ exclusion.

Highlights

Quartz sand experiments confirmed that QXN233 grew considerably well; the height, leaf width and length, and fresh weights (FWs) all increased under salt stress when treated with 3 mM Pi (Fig. 1A; Table 1)
P, an essential macronutrient, was measured in the present study, and the results showed that Pi (3 mM Pi) in Hoagland’s nutrient solution alleviated the salt injury of maize seedlings under 200 mM NaCl stress (Fig. 1; Figs S2–S5), which might be related to the accumulation of compatible solutes, reduced reactive oxygen species (ROS) levels and increased Na+ exclusion
We reveal that the salt tolerance of maize could be improved by exogenous Pi applications at the seedling stage

Summary

Introduction

Consistent with the increased tolerance, the total number of roots and the growth of shoots increased to relieve salt stress This phenomenon could be associated with the observed increased expression of nitrate transporters. Plants adapt to salinity stress by employing various measures, including the exclusion of Na+ and/or its sequestration into the vacuole, the accumulation of compatible solutes, and the effective scavenging of reactive oxygen species (ROS)[10,11,12,13]. For maize seedlings, salt tolerance is associated with the ability to remove Na+ and retain potassium (K+), and the growth reduction might be due to a decrease in K+ levels in the leaves or roots[16,17]. The interaction between salt and Pi and the mechanism underlying the effects of Pi on the salt tolerance of plants are still unclear and need to be further elucidated

Methods

Results

Discussion

Conclusion