Abstract: Taking the seedlings of mulberry (Morus alba) varieties Qiuyu and Tailai from Heilongjiang Province as test materials, this paper studied their growth, leaf water relations, and ion distribution in various organs under the stress of different salt concentration. The results showed that salt stress decreased the plant height and dry mass of the seedlings obviously, and the dry mass of young leaves was more affected than that of old leaves. With increasing salt stress, leaf water potential, osmotic potential, pressure potential, and relative water content decreased markedly, while the Na+ concentration in root and stem had an obvious increase. When the soil NaCl concentration was 150 mmol·L-1 or higher, the Na+ concentration in leaf, stem, and root reached saturated. Salt stress markedly decreased the K+ and Ca2+ concentrations in leaf, stem, and root as well as the Mg2+ concentration in leaf and stem, but had lesser effects on the Mg2+ concentration in root. The decrease of leaf Ca2+, K+, and Mg2+ concentrations under salt stress caused the ion deficiency in plant and limited plant growth, while the regionalized distribution of Na+ in root, stem, and older leaf could be one of the salt tolerance mechanisms of test varieties.

Key words: tree ring, δ¹³C,  , ring width, Pinus sylvestris var. mongolica.