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Uptake of 15 NO 2 by sunflower ( Helianthus annum ) during exposures in light and darkness: quantities, relationship to stomatal aperture and incorporation into different nitrogen pools within the plant
Author(s) -
SEGSCHNEIDER HANSJOSEF,
AND JÜRGEN WILDT,
FÖRSTEL HILMAR
Publication year - 1995
Publication title -
new phytologist
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.742
H-Index - 244
eISSN - 1469-8137
pISSN - 0028-646X
DOI - 10.1111/j.1469-8137.1995.tb03060.x
Subject(s) - helianthus annuus , darkness , nitrogen , nitrate reductase , photosynthesis , sunflower , nitrogen assimilation , nitrate , assimilation (phonology) , chemistry , botany , nitrite reductase , reactive nitrogen , nitrogen deficiency , horticulture , biology , linguistics , philosophy , organic chemistry
summary Exposures of sunflowers ( Helianthus annuus L. var. Giganteus) to 15 NO 2 , at concentrations between 5.0 and 72.9 ppb resulted in its uptake by the plants during illumination as well as during darkness. The NO 2 , flux increased linearly with increasing NO 2 , concentrations in both treatments. Evolution of NO 2 by sunflowers was not observed. During illumination, measured and potential N Of uptake were equal, which indicates that the uptake of NO 2 was only limited by stomatal resistance, whereas in darkness, an additional internal resistance to NO. cannot be excluded. After 15 NO 2 , exposures, the highest proportions of the 15 N tracer were fixed as protein nitrogen or as heterocyclic nitrogen compounds and glucosamine. Under both treatments there were remarkably high 15 N enrichments in the fraction ‘soluble amino acid nitrogen’, indicating a rapid assimilation of the nitrogen derived from 15 NO 2 , A linear relation was found between the δ 15 N values of nitrogen pools investigated and the 15 NO 2 concentrations after exposures in light as well as after night‐time fumigation. Apparently, all the enzyme systems involved in the assimilation of the NO 2 nitrogen must be available in sufficient amounts in plant tissues during exposures. Even after exposures in the dark, about 95% of the absorbed 15 NO 2 , nitrogen was fixed in reduced organic nitrogen compounds, which indicates that the assimilation of atmospheric NO 2 , might not depend on the production of reduction equivalents by photosynthesis. The mechanism of NO, assimilation via nitrate/nitrite reductase within the exposed sunflowers is discussed.