Subcellular Localization of Zinc and Calcium in Bean (Phaseolus vulgaris L.) Tissues

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Abstract
Two bean (Phaseolus vulgaris L.) cultivars differing in growth responses to zinc were examined for differences in uptake and subcellular localization of 65Zn during a 15-day growth period. The zinc-sensitive cultivar Sanilac showed initially a much higher rate of absorption, which declined after 24 hours. The zinc-tolerant cultivar Saginaw showed a slow but steady rate of absorption for 10 days. In roots as well as in stem callus tissues of both cultivars, three-fourths of the absorbed 65Zn was localized in the “cytoplasmic” supernatant fractions (containing ribosomes and vacuolar sap). Very little (less than 7%) 65Zn was localized in the cell wall fraction. There was a much greater proportion of the absorbed 65Zn localized in root mitochondria and nuclei of the zinc-sensitive Sanilac than in the zinc-tolerant Saginaw. Stem callus tissues, however, did not show such cultivar differences in zinc accumulation at the sub-cellular level.
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