Absorption and allocation characteristics of K+, Ca2+, Na+ and Cl- in different organs of Broussonetia papyrifera seedlings under NaCl stress.

One-year-old Broussonetia papyrifera seedlings were subjected to 0.4,1,2,3, and 4 g·kg-1 of soil NaCl stress, and their biomass accumulation, leaf plasma membrane permeability, and the absorption, allocation and translocation of K⁺, Ca²⁺, Na⁺, and Cl^-, as well as the symptoms of salt injury, were studied and investigated. The leaf plasma membrane permeability increased with the increase of soil NaCl concentration and of the duration of soil NaCl stress, and the seedling's root/shoot ratio also increased with increasing soil NaCl concentration. When the soil NaCl concentration exceeded 3 g·kg^-1, leaf plasma membrane permeability and seedling's biomass accumulation were affected significantly. The Na⁺ and Cl^- concentrations in different organs of seedlings increased with increasing soil NaCl concentration while the K⁺ and Ca²⁺ concentrations were in adverse, and the ion contents in leaves were always much higher than those in other organs, illustrating that soil NaCl stress affected the K⁺ and Ca²⁺ absorbing capability of roots, and inhibited the selective translocation of K⁺ and Ca²⁺ to aboveground parts. As a result, the K⁺ and Ca²⁺ concentrations in leaves and stems decreased. The study showed that B. papyrifera could effectively resist the injury of osmotic stress from soil salt via absorbing and accumulating Na⁺ and Cl^-, but excessive accumulation of Na⁺ and Cl^- could induce salt toxicity. As a non-halophyte species with relatively strong salt resistance, the aboveground parts of B. papyrifera did not have significant salt-exclusion effect. [ABSTRACT FROM AUTHOR]