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Verteilung von Stickstoff auf Sproß und Wurzel bei jungen Bohnenpflanzen nach der Aufnahme von NO 3 − und NH 4 +
Author(s) -
Martin P.
Publication year - 1976
Publication title -
zeitschrift für pflanzenernährung und bodenkunde
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.644
H-Index - 87
eISSN - 1522-2624
pISSN - 0044-3263
DOI - 10.1002/jpln.19761390206
Subject(s) - shoot , phaseolus , nitrate reductase , chemistry , chromosomal translocation , nitrogen , horticulture , nitrate , nutrient , biology , biochemistry , organic chemistry , gene
Translocation of nitrogen to the shoot of young bean plants after uptake of NO 3 −and NH 4 +by the root Phaseolus vulgaris plants (var. nana , cv. Saxa) at the primary leaf stage (without nodules) were fed during 6 hours with 15 NO 3 −and 15 NH 4 + , respectively. 24 hours after the absorption period more 15 N from the absorbed NO 3 −was translocated from the root to the shoot. The presence of NH 4 +in the nutrient solution enhanced the translocation of 15 NO 3 − N, probably by an inhibition of nitrate reductase. NH 4‐ + 15 N is mainly retained in the root by a high incorporation into the root protein. It can be concluded that nitrogen from newly absorbed NO 3 −is not retained and used for protein synthesis in the root according to the root's potential to synthesize protein. Nitrate reduction in the root is considered to be the limiting factor. This is supported by the fact that withdrawal of NO 3 −in the nutrient solution prior to the 15 N‐experiment increased NO 3 − translocation to the shoot as a consequence of a lowered level of nitrate reductase. In an experiment with 14 NO 3 − supply to the roots and 15 NO 3 − application to the primary leaves (infiltration method) a considerable amount of 15 N was translocated from the leaves to the roots. This indicates that an insufficient NO 3 − reduction in the root can be substituted by a retranslocation of reduced N‐compounds from leaves to the roots. The proportion of NO 3 −reduced in the root influences also the pattern of primary distribution of nitrogen in the shoot of plants at the 4 leaf stage. At a concentration of 0,2 meq/l NO 3 −in the nutrient solution as compared to 20 meq/l NO 3 −during 10 hours a relative higher amount of 15 N was transported from the root to the younger, growing leaves i.e. via the phloem to metabolic sinks.