NITRATE ACCUMULATION BY WHEAT (TRITICUM-AESTIVUM) IN RELATION TO GROWTH AND TISSUE-N CONCENTRATIONS

The accumulation of nitrate in relation to total N concentrations ([N]i) in tissues of wheat (Triticum aestivum L., cv Sicco) grown in solution culture was investigated. Root, shoot and leaf tissues showed qualitatively similar relationships between internal nitrate concentrations and [N]i, both expressed on a tissue water basis. At low [N]i, no nitrate was detectable but once a particular [N]i was exceeded, nitrate accumulated as a linear function of [N]i. The threshold [N]i values for nitrate accumulation were 110, 450, and 550 m M for roots, total shoot and leaf 4, respectively. The slope of the relationship between nitrate and [N]i indicated that in all tissues nitrate accounted for 50-55% of the extra N accumulated above the threshold [N]i. All growth requirements for N were satisfied before nitrate accumulated. © 1990 Kluwer Academic Publishers.