Effect of Vanadate on Bean Leaf Movement, Stomatal Conductance, Barley Leaf Unrolling, Respiration, and Phosphatase Activity

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Abstract
Vanadate (Na3VO4) inhibits leaf movement and stomatal conductance of P. vulgaris L. cv. Carlos Favorit in light-dark cycles as well as photomorphogenetic leaf unrolling of H. vulgare L. cv. Rupal. Inhibition was 50% by 10-100 .mu.M vanadate and 100% by mM vanadate. Leaf unrolling was also inhibited by oligomycin and diethylstilbestrol. Millimolar vanadate is required to affect respiration of bean plants and barley leaves, while even this concentration has no effect on respiration of isolated pulvinal tissue. Nonspecific phosphatase activity extracted from both bean pulvini and barley leaves occurred in all 4 fractions of a differential centrifugation procedure (i.e., cell walls plus nuclei, mitochondria, microsomes, supernatant), but more than 90% of the specific and total activity was located in the supernatant. The phosphatase activities of all fractions were inhibited by concentrations of vanadate similar to those which inhibited leaf movement, stomatal conductance of bean, and unrolling of barley leaves.