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Fate of nitrate during initial nitrate utilization by nitrogen‐depleted dwarf bean
Author(s) -
BRETELER HANS,
CATE CHARLOTTE H. HÄNISCH TEN
Publication year - 1980
Publication title -
physiologia plantarum
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.351
H-Index - 146
eISSN - 1399-3054
pISSN - 0031-9317
DOI - 10.1111/j.1399-3054.1980.tb03257.x
Subject(s) - nitrate , nitrate reductase , phaseolus , nitrogen , chemistry , xylem , shoot , horticulture , botany , biology , organic chemistry
The fate of nitrate and nitrogen‐15 was followed during the apparent induction phase (6h) for nitrate uptake by N‐depleted dwarf bean ( Phaseolus vulgaris L. ev. Witte Krombek). Experiments were done with intact plants and with detached root systems. Qualitatively and quantitatively, xylem exudation from detached roots was a bad estimate of the export of NO − 3 or NO − 3 ‐ 15 N from roots of intact plants. In vivo nitrate reductase activity (NRA) agreed well with in situ reduction, calculated as the difference between uptake and accumulation in whole plants, provided NRA was assayed with merely endogenous nitrate as substrate (‘actual’ NRA). The majority (75%) of the entering nitrate remained unmetabolized. Both nitrate reduction and nitrate accumulation occurred predominantly in the root system. Some (< 25%) of the root‐reduced nitrate‐N was translocated to the shoot. Nitrate uptake occurred against the concentration gradient between medium and root cells, and probably against the gradient of the electro‐chemical potential of nitrate. Part of the energy expended for NO − 3 absorption came from the tops, since decapitation and ringing at the stem base restricted nitrate uptake.