Identification of the leaf vacuole as a major nitrate storage pool |
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Authors: | Granstedt R C Huffaker R C |
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Institution: | Plant Growth Laboratory and Department of Agronomy & Range Science, University of California at Davis, Davis, California 95616. |
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Abstract: | Highly purified vacuoles were isolated from protoplasts derived from green barley (Hordeum vulgare var. Numar) leaves, in order to determine their role as a NO3− storage sink. α-Mannosidase and acid phosphatase activities were used as markers to identify vacuoles, α-mannosidase being the more suitable. Nitrate and α-mannosidase, which were released from vacuoles destroyed during lysis of protoplasts, moved at unequal rates in the density gradient used for vacuole isolation. Purified vacuoles retained less NO3− than α-mannosidase during a single washing. Empirically determined corrections were used to account for NO3− movement in estimating the percentage of total cellular nitrate found in the vacuole. Vacuoles from plants grown in the presence of NO3− contained 58% of the total cellular NO3− and therefore represent a major NO3− storage pool. |
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