The nitrogen balance of Raphanus sativus x raphanistrum plants. II. Growth, nitrogen redistribution and photosynthesis under NO3 deprivation


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Abstract. Wild radish plants deprived of, and continuously supplied with solution NO 3 for 7 d following 3 weeks growth at high NO 3 supply were compared in terms of changes in dry weight, leaf area, photosynthesis and the partitioning of carbon and nitrogen (NH2‐N and NO 3‐N) among individual organs. Initial levels of NO 3‐N accounted for 25% of total plant N. Following termination of NO 3 supply, whole plant dry weight growth was not significantly reduced for 3 d, during which time plant NH2‐N concentration declined by about 25% relative to NO 3‐supplied plants, and endogenous NO 3‐N content was reduced to nearly zero. Older leaves lost NO 3 and NH2‐N, and roots and young leaves gained NH2‐N in response to N stress. Relative growth rate declined due both to decreased net assimilation rate and a decrease in leaf area ratio. A rapid increase in specific leaf weight was indicative of a greater sensitivity to N stress of leaf expansion compared to carbon gain. In response to N stress, photosynthesis per unit leaf area was more severely inhibited in older leaves, whereas weight‐based rates were equally inhibited among all leaf ages. Net photosynthesis was strongly correlated with leaf NH2‐N concentration, and the relationship was not significantly different for leaves of NO3 ‐supplied compared to NO 3‐deprived plants. Simulations of the time course of NO 3 depletion for plants of various NH2‐N and NO 3 compositions and relative growth rates indicated that environmental conditions may influence the importance of NO 3 accumulation as a buffer against fluctuations in the N supply to demand ratio.

Original languageEnglish (US)
Pages (from-to)755-767
Number of pages13
JournalPlant, Cell and Environment
Issue number8
StatePublished - 1988
Externally publishedYes



  • Brassicaceac
  • growth
  • nitrate accumulation
  • partitioning
  • photosynthesis
  • Raphanus sativus
  • redistribution

ASJC Scopus subject areas

  • Physiology
  • Plant Science

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