Interaction between mild salinity and sublethal SO 2 pollution on wheat ( Triticum aestivum cultivar ‘Wilgoyne’ (Ciano/Gallo)). II. Accumulation of sulphur and ions

Abstract

Wheat ( Triticum aestivum cultivar ‘Wilgoyne’ (Ciano/Gallo)) plants wer exposed to a factorial combination of two levels of salinity (control and 50 mM NaCl), and three levels of SO 2 (<10, 231, and 441 nl 1 −1) in fumigation chambers with rain-exclusion tops for 4 h day −1 for up to 42 days. The study was to investigate whether mild salinity stress could influence the accumulation and reduction of SO 2 absorbed and SO 2 fumigation could modify the salt ion concentrations in the plant tissues. SO 2 fumigation significantly increased sulphur concentration in the shoots, but not in the roots. The SO 2 absorbed in the leaves was mostly oxidized into sulphate and little reduced into organic sulphur compounds. NaCl salinity decreased the sulphate concentration in leaves, but did not affect the organic sulphur concentration. There was an antagonistic interaction between SO 2 fumigation and NaCl salinity on the concentration of sulphate in the leaves. SO 2 fumigation, salinity, and their combination affected the concentrations of Cl −, K +, Na +, Ca 2+ and Mg 2+ in the plant tissues Exposure to SO 2 increased the K + concentration in the leaves, but decreased the Cl −, Ca 2+ and Mg 2+ concentrations. SO 2 fumigation and NaCl salinity had an antogonistic interaction on the concentrations of K +, Cl −, Ca 2+ and Mg 2+ in the leaf tissue. The Na + concentration in the youngest fully expanded leaves of the saline plants was decreaed by exposure to 441 nl 1 −1 SO 2. Plant tolerance to NaCl salinity may have been enhanced by SO 2 fumigation by decreasing Na + and Cl − concentration and increasing the K + concentration in the leaves. The antagonistic interactions between SO 2 fumigation and NaCl salinity on the SO 2 uptake and salt accumulation in the leaves may be responsible for their anatogonistic interaction on plant growth.