CHARACTERIZATION OF Zn EFFICIENCY IN IRANIAN RICE GENOTYPES I. UPTAKE EFFICIENY

Zn deficiency is one of the most important micro-nutritional disorders in lowland rice. In this work, fourteen Iranian rice cultivars were studied in the field as well as in solution culture experiments to determine genotypic differences for traits characterizing Zn efficiency. A low uptake efficiency was observed in some (Onda and Kadoos) of the Zn-inefficient genotypes. A relatively high correlation (r=0.77) could be found between Zn content but not Zn concentration of shoot and dry matter production of genotypes. On the other hand, partitioning of applied Zn to soil was different between vegetative and generative parts of plants depending on genotypes. In Onda and Kadoos (Zn-inefficient) accumulation of Zn occurred in straw while in Nemat and Shafagh (Zn-efficient) the major portion of Zn taken up by plants was accumulated in seeds. A change measured in nutrient solution pH was higher in older than younger, in deficient than sufficient and in Zn-efficient than Zn-inefficient plants. It could be concluded that uptake efficiency, particularly in combination with a higher acidification potential of the rhizosphere, could be an important mechanism for the differences in studied rice genotypes.