Nitrate Reductase Activity in Maize (Zea mays L.) Leaves: II. Regulation by Nitrate Flux at Low Leaf Water Potential 1

摘要

Experiments were conducted to determine whether the nitrate flux to the leaves or the nitrate content of the leaves regulated the nitrate reductase activity (NRA) in leaves of intact maize (Zea mays L.) seedlings having low water potentials (ψw) when other environmental and endogenous factors were constant. In seedlings that were desiccated slowly, the nitrate flux, leaf nitrate content, and NRA decreased as ψw decreased. The decrease in nitrate flux was caused by a decrease in both the rate of transpiration and the rate of nitrate delivery to the transpiration stream. Upon rewatering, the recovery in NRA was correlated with the nitrate flux but not the leaf nitrate content.