The regulation of accumulation and secretion of several major inorganic cations by Chinese Iris under NaCl stress

Chinese Iris (Iris lactea Pall. var. chinensis (Fisch.) Koidz.) is a monocotyledonous halophyte, which is considered an important salt-tolerant species. In this study, the plant growth, ion absorption and transportation and leaf secretion characteristics of Iris under sodium chloride (NaCl) stress were investigated using nutrient solutions with four NaCl concentrations ranging from 0 to 300 mmol L−1. The main results indicated that Na+ secretion accounted for 5.7–11.5% of the ion distribution pattern of 90% of the ions accumulated in vivo by Iris. The ion transportation ratio was potassium > magnesium > calcium > sodium, (K+ > Mg2+ > Ca2+ > Na+), K+/Na+, Ca2+/Na+, Mg2+/Na+ in the shoot were greater than those in the root. K–Na and Ca–Na selectivity ratios showed an increasing trend overall. The contribution of salt secretion to the salt tolerance of Iris was tiny, which will be discussed in further research, achieving ion balance in vivo through selective absorption and transportation under salt stress is undoubtedly a primary salt-tolerance adaptation mechanism of Iris.