Ethylene, a possible cause for the changed NA⁺ inter-organ distribution in NaCl-stressed tomato plants under anoxia

Poor root-zone aeration is known to decrease salt tolerance in many plants. Plants of Lycopersicon esculentum L. cv. M-82 were grown in the Hoagland nutrient solutions containing NaCl at concentrations of 0, 50, and 100 mM for one week. Root anoxia treatments were then given by bubbling with pure N ₂ through the solution (Ni-bubbling), or stopping bubbling at all (no-bubbling). The plant fresh weight (FW) and dry weight (DW) were recorded and the level of Na⁺ in different organs was analyzed. Both salt and anoxia caused the reduction of plant growth in terms of both FW and DW. Sodium levels increased in root, stem, and leaf with the increase of NaCl concentration in root media. After 48 h of anoxia, the total Na⁺ content was much higher (especially under no-bubbling) relatively to the control (air-bubbling). Sodium concentration was lower in root and stem, and higher in the leaf as compared to the control. The lowest level in the root and stem, and the highest level in the leaf occurred in plants with no-aeration. The possible causes for the changes in Na⁺ inter-organ distribution are discussed.