CRITICAL DEFICIENCY CONCENTRATION OF ZINC IN BARLEY GENOTYPES DIFFERING IN ZINC EFFICIENCY AND ITS RELATION TO GROWTH RESPONSES

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Abstract
A growth room study was conducted to compare responses to zinc of two barley (Hordeum vulgare L. cw. Tarm and Hamidiye) genotypes differing in zinc (Zn) efficiency and to determine a critical deficiency concentration of Zn in tissue. Two genotypes of barley, Tarm (Zn efficient) and Hamidiye (Zn inefficient), were grown in a Zn deficient siliceous sand with Zn added at 10 Zn rates (0, 0.04, 0.08, 0.1, 0.2, 0.4, 0.8, 1.6, 3.2, and 6.4 mg Zn/kg dry soil). Visual Zn deficiency symptoms, such as inhibition of shoot elongation and development of chlorotic areas on leaves, appeared more rapidly and severely in Hamidiye when Zn supply was deficient ( < 0.08 mg/kg), while those symptoms in Tarm were slightly visible only when no Zn was applied. Tarm had greater shoot and root dry matter than Hamidiye until Zn fertilization reached 0.8mg/kg fertilization rate at which both genotypes achieved their maximal growth. Beyond this rate, both genotypes had similar yields. Zn concentration and content were increased progre...