Na‐Ca interactions in barley seedlings: relationship to ion transport and growth

Abstract

Abstract Salt‐stressed plants often show Ca deficiency symptoms. The effects of NaCl salinity (1 to 150 mol m‐3) and supplemental Ca (10 mol m‐3) on Na and Ca transport in barley (Hordeum vulgare L.) and their relationship to growth were investigated. The adjustment of Na and Ca transport was investigated by examining young seedlings exposed to short‐term (immediate) and long‐term (7 d) exposure to salinity. When the plants were exposed to long‐term treatments of salinity, the rate of sodium accumulation in roots was approximately 10 to 15% of short‐term treatments. No significant adjustment in the transport to the shoot was observed. Rates of tracer (22Na) transport were compared to calculated rates based on relative growth rates and tissue element concentrations. Comparisons between measured tracer and calculated rates of transport indicate that 22Na transport may underestimate transport to the shoot because of dilution of the tracer in the root cytoplasm. Calcium uptake showed only minor adjustment with time. Measured rates of tracer transport to the shoot correlated well with calculated values. The transport and tissue concentrations of Na were significantly affected by supplemental Ca. Calcium transport and tissue concentrations were markedly inhibited by salinity. Supplemental Ca increased Ca transport and accumulation at all NaCl treatments above that of control plants without supplemental Ca. Salinity inhibited plant growth at 150 mol m ‐3NaCl, but not at 75 mol m‐3.Supplemental Ca significantly improved root length but not fresh weight after 7d of salinity, although differences in fresh weight were detected after 9d. There were significant Na‐Ca interactions with ion transport, ion accumulation, and growth. The effects of salinity on Na and Ca transport to the shoot do not appear to play a major role in shoot growth of barley.