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

Vanadate (Na(3) VO(4)) inhibits leaf movement and stomatal conductance of Phaseolus vulgaris L. cv. Carlos Favorit in light-dark cycles as well as photomorphogenetic leaf unrolling of Hordeum vulgare L. cv. Rupal. Inhibition was 50% by 10 to 100 micromolar vanadate and 100% by millimolar 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.A nonspecific phosphatase activity extracted from both bean pulvini and barley leaves was found in all of four fractions of a differential centrifugation procedure (i.e. cell walls + nuclei, mitochondria, microsomes, super-natant), 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.