Mitigation impacts of localized salt replacement on the salinity damage of cucumber: The relationship between cucumber growth and salt level in the root region

Salinity is rarely homogeneous in soil under the natural environment, and the ranges of soil salinity distributed in the plant root zone can vary widely. The purposes of this research were to investigate the effects of inhomogeneous salinity on cucumber growth and to explore the correlation between plant growth and salinity in the root region by a root-splitting method. Both laterals of the root were treated with either the same (0/0, 25/25, 50/50 and 75/75 mM) or different concentrations of NaCl (0/75, 25/75, 50/75 and 0/100 mM). Compared with homogeneous salinity, compensatory water uptake and compensatory growth of the roots on the low-salt side of inhomogeneous salinity happened and the shoot also grew better. Meanwhile, the levels of soluble sugar, proline, and MDA in leaves were lower than those of homogeneous salinity. Cucumber growth and osmotic adjustment substances responded most closely to root-weighted mean salinity based on the resulting combined data. These findings indicate that inhomogeneous salinity can alleviate the damage to cucumber seedlings caused by salt stress by reducing the average salt concentration in the root zone and enhancing osmoregulation.