The nitrogen balance of Raphanus sativus X raphanistrum plants. I. Daily nitrogen use under high nitrate supply

E. ‐D SCHULZE, George W Koch, F. PERCIVAL, H. A. MOONEY, C. CHU

Research output: Contribution to journalArticlepeer-review

11 Scopus citations

Abstract

Abstract Growth‐chamber cultivated Raphanus plants accumulate nitrate during their vegetative growth. After 25 days of growth at a constant supply to the roots of 1 mol m−3 (NO3) in a balanced nutrient solution, the oldest leaves (eight‐leaf stage) accumulated 2.5% NO3‐nitrogen (NO3‐N) in their lamina, and almost 5% NO3‐N in their petioles on a dry weight basis. This is equivalent to approximately 190 and 400 mol−3 m−3 concentration of NO3 in the lamina and the petiole, respectively, as calculated on a total tissue water content basis. Measurements were made of root NO3 uptake, NO3 fluxes in the xylem, nitrate uptake by the mesophyll cells, and nitrate reduction as measured by an in vivo test. NO3 uptake by roots and mesophyll cells was greater in the light than in the dark. The NO3 concentration in the xylem fluid was constant with leaf age, but showed a distinct daily variation as a result of the independent fluxes of root uptake, transpiration and mesophyll uptake. NO3 was reduced in the leaf at a higher rate in the light than in the dark. The reduction was inhibited at the high concentrations calculated to exist in the mesophyll vacuoles, but reduction continued at a low rate, even when there was no supply from the incubation medium. Sixty‐four per cent of the NO3 influx was turned into organic nitrogen, with the remaining NO3 accumulating in both the light and the dark.

Original languageEnglish (US)
Pages (from-to)713-720
Number of pages8
JournalPlant, Cell and Environment
Volume8
Issue number9
DOIs
StatePublished - 1985
Externally publishedYes

Keywords

  • nitrate accumulation
  • nitrate reduction
  • nitrate transport
  • nitrate uptake
  • Raphanus

ASJC Scopus subject areas

  • Physiology
  • Plant Science

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