BORON TOXICITY IN BARLEY (HORDEUM-VULGARE L) SEEDLINGS IN RELATION TOSOIL-TEMPERATURE

Boron (B) is an essential micronutrient in crop growth but its suffici ency range is narrow. Boron toxicity is a widespread problem in arid a nd semi-arid areas with cold weather. We investigated the effect of so il temperature (5, 10 and 15 degrees C) on development of symptoms of B toxicity, plant growth and plant development, and on content and con centration of B in tissue of seedlings of four barley lines grown in s oil with high level of available B (12 mg kg(-1)). Visual symptoms of toxicity were first observed in the high B soil concentration treatmen t at 5 degrees C at 12 days after emergence. Concentration of B in tis sue decreased with increasing soil-temperatures. There was no effect o f soil temperature on B content or B concentration in plant tissue at the final sample (17 days after emergence). High soil B reduced seedli ng and leaf emergence rates, although the final seedling emergence and number of leaves were unaffected. Barley lines differed in concentrat ion of B in tissues and visual toxicity symptom development. Adaptatio n to high B was either through maintaining low tissue B concentration or through tolerance to high tissue B concentration. While the investi gated range of temperature does influence B toxicity in barley seedlin gs, it remains to be determined whether it affects crop yield.