Regulation of nitrate uptake in a whole plant perspective. Changes in influx and efflux of nitrate in spinach.

When leafy vegetables, like spinach and lettuce, are grown in greenhouses during winter and early spring, they may accumulate a high amount of nitrate in the leaves. A high nitrate content in vegetables is undesirable because it may be harmful for the consumer. Nitrate itself is not toxic, but it is easily reduced to the toxic compound nitrite. At present, standards for maximum acceptable nitrate concentrations in vegetables are being set in the European Community. During winter, the nitrate concentration in lettuce and spinach in The Netherlands often exceeds the permitted level, which puts a high pressure on efforts to lower the nitrate content in these vegetables. There is a need for more knowledge of the physiological processes that lead to the accumulation of nitrate in the leaves, like the nitrate uptake by the roots, the assimilation of nitrate to amino acids and proteins and the relation of these processes with the C metabolism and plant growth. ... Zie: Summary