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Interaction between atmospheric and pedospheric nitrogen nutrition in spruce ( Picea abies L. Karst) seedlings
Author(s) -
MULLER B.,
TOURAINE B.,
RENNENBERG H.
Publication year - 1996
Publication title -
plant, cell and environment
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.646
H-Index - 200
eISSN - 1365-3040
pISSN - 0140-7791
DOI - 10.1111/j.1365-3040.1996.tb00257.x
Subject(s) - fumigation , picea abies , xylem , nitrogen , shoot , exudate , chemistry , horticulture , nutrient , botany , karst , agronomy , biology , paleontology , organic chemistry
The effect of NO 2 fumigation on root N uptake and metabolism was investigated in 3‐month‐old spruce ( Picea abics L. Karst) seedlings. In a first experiment, the contribution of NO 2 to the plant N budget was measured during a 48 h fumigation with 100mm 3 m −3 NO 2 . Plants were pre‐treated with various nutrient solutions containing NO 2 and NH 4 + , NO 3 − only or no nitrogen source for 1 week prior to the beginning of fumigation. Absence of NH 4 + in the solution for 6d led to an increased capacity for NO 3 − uptake, whereas the absence of both ions caused a decrease in the plant N concentration, with no change in NO 3 − uptake. In fumigated plants, NO 2 uptake accounted for 20–40% of NO 3 − uptake. Root NO 3 − uptake in plants supplied with NH 4 + plus NO 3 − solutions was decreased by NO 2 fumigation, whereas it was not significantly altered in the other treatments. In a second experiment, spruce seedlings were grown on a solution containing both NO 2 and NH 4 + and were fumigated or not with 100mm 3 m −3 NO 2 for 7 weeks. Fumigated plants accumulated less dry matter, especially in the roots. Fluxes of the two N species were estimated from their accumulations in shoots and roots, xylem exudate analysis and 15 N labelling. Root NH 4 + uptake was approximately three times higher than NO 3 − uptake. Nitrogen dioxide uptake represented 10–15% of the total N budget of the plants. In control plants, N assimilation occurred mainly in the roots and organic nitrogen was the main form of N transported to the shoot. Phloem transport of organic nitrogen accounted for 17% of its xylem transport. In fumigated plants, neither NO 3 − nor NH 4 + accumulated in the shoot, showing that all the absorbed NO 2 was assimilated. Root NO 3 − reduction was reduced whereas organic nitrogen transport in the phloem increased by a factor of 3 in NO 2 ‐fimugated as compared with control plants. The significance of the results for the regulation of whole‐plant N utilization is discussed.