Effects of salt stress on ion dynamics and the relative expression level of salt tolerance genes in peanut seedlings
Abstract
Different peanut varieties have different salt tolerance. In this study, to determine the flow rates of ions Na+, K+, Ca2+, NH4+, NO3-, and Cl- in root tips of peanut seedlings under salt stress via Non-invasive Micro-test technique, a salt-tolerant peanut variety Huayu 25 (HY25) and a salt-sensitive variety Huayu 20 (HY20) were used as the experimental materials. The growth traits, the relative expression level of major salt tolerance genes, and the contents of osmotic regulatory substances (soluble sugar and proline) were also measured to establish the difference of ion absorption and stress resistance regulation in different varieties. The results showed as follows: (1) Under NaCl stress, Na+ influx was inhibited, and its efflux increased, but promoted the influx of K+. The efflux rate of Na+ and influx rate of K+ in HY25 were higher than HY20, which may improve salinity tolerance by preserving K+ and discharging Na+. (2) Salt stress promoted Ca2+ influx, and the Ca2+ influx rate of salt-tolerant varieties was higher than the salt-sensitive varieties, which might be related to salt tolerance. (3) NO3- exhibited efflux in both varieties under salt stress, but the efflux rate of the salt-tolerant variety HY25 was lower, indicating that HY25 could resist the harm of salt stress by slowing the loss of NO3-. (4) Salt stress induced Cl- efflux in HY25 but influx in salt-sensitive variety, indicating that HY25 could reduce the toxicity of Cl- by accelerating the efflux of Cl-. (5) Salt stress significantly up-regulated the relative expression level of salt-tolerant genes AhNHX1, AhHA1, AhSAMDC1, and AhLeaD in salt-tolerant variety HY25, which could help improve its salt tolerance. Clarifying the dynamic changes of root ion flow and resistance mechanism under salt stress can provide the theoretical support for improving the emergence, establishment, and development of peanut seedlings in saline-alkali land and the establishment of regulation technology.