PATTERN OF SUPPLY AFFECTS BORON TOXICITY IN BARLEY

Barley (Hordeum vulgare L., cv. Stirling) was grown in pots of a sandy soil to which six levels of boron (B) were added presowing, during st em elongation, or during ear emergence. The pattern of B supply affect ed the development of leaf injury and other symptoms of B toxicity, th e accumulation of B in the grain and in the whole shoots (WS) at matur ity, and the relationships between the concentrations of B in the grai n and in the WS at maturity and yield. Critical toxic concentrations ( CTC) of B in plant tissues were found to vary from approximately 2 to 15 mu g/g, and from approximately 50 to 420 mu g/g, respectively. The findings of this experiment suggest that barley plants can accumulate relatively high levels of B and express severe levels of leaf injury a nd other symptoms of B toxicity in the latter stages of growth with re latively small effects on grain yield. They also suggest that the grai n and the WS sampled at maturity are not suitable tissues for the diag nosis of yield depressions due to B toxicity in Stirling barley.