, Volume 52, Issue 4, pp 589–596 | Cite as

Effects of supplementary potassium nitrate on growth and gas-exchange characteristics of salt-stressed citrus seedlings

  • D. Khoshbakht
  • A. Ghorbani
  • B. Baninasab
  • L. A. Naseri
  • M. Mirzaei
Original Papers


We investigated the effects of supplementary KNO3 and NaCl on one-year-old, potted Valencia orange (Citrus sinensis) scions grafted on Iranian mandarin Bakraii [Citrus reticulate × Citrus limetta] (Valencia/Bakraii) and Carrizo citrange [C. sinensis × Poncirus trifoliata] (Valencia/Carrizo) rootstocks. After watering plants for 60 days with 50 mM NaCl, the lowest reduction in dry mass, stomatal conductance, and chlorophyll (Chl) content was found in Valencia/Bakraii. Bakraii accumulated more Cl and Na+ in roots and transferred less to Valencia leaves compared with Carrizo rootstock. Moreover, higher net photosynthetic rate was found in Valencia/Bakraii than those on Carrizo rootstock. NaCl caused a decrease in the maximal efficiency of PSII photochemistry (Fv/Fm) and effective quantum yield (ΦPSII) but elevated coefficient of nonphotochemical quenching. Salinity reduced Ca2+, Mg2+, and total N contents, and increased Na+/K+ ratio in leaves and roots of both grafting combinations. Salinity increased K+ and proline content in leaves and decreased K+ concentrations in roots of both grafting combinations. In salinized plants, nitrate supplementation (10 mM KNO3) reduced leaf abscission, Cl, Na+, Na+/K+, and Ca2+ concentrations in leaves and roots of both combinations. K+ and N concentrations and proline increased in leaves of the nitrate-supplemented salinized plants. Supplementary nitrate increased leaf number and area, stem elongation, Chl content, Fv/Fm, and ΦPSII and stimulated photosynthetic activity. Thus, nitrate ameliorated the deleterious effects of NaCl stress and stimulated the plant metabolism and growth. It can be used as a vital treatment under such condition.

Additional key words

chlorophyll fluorescence mineral nutrition net gas exchange nitrogen rootstocks salinity 



atmospheric CO2 concentration




dry mass


fresh mass


minimal fluorescence yield of the dark-adapted state


maximal fluorescence yield of the dark-adapted state


maximal fluorescence of the light-adapted state


steady-state fluorescence


maximum photochemical efficiency of PSII


stomatal conductance


nonphotochemical quenching


net photosynthetic rate


NaCl salinity stress


NaCl + KNO3


effective quantum yield of PSII photochemistry


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Copyright information

© The Institute of Experimental Botany 2014

Authors and Affiliations

  • D. Khoshbakht
    • 1
  • A. Ghorbani
    • 2
  • B. Baninasab
    • 1
  • L. A. Naseri
    • 3
  • M. Mirzaei
    • 4
  1. 1.Department of Horticultural Science, College of AgricultureIsfahan University of TechnologyIsfahanIran
  2. 2.Department of Horticultural Science, College of AgricultureAzad UniversityMakooIran
  3. 3.Department of Horticultural Science, College of AgricultureUniversity of UrmiaWest AzarbaijanIran
  4. 4.Department of Horticultural Science, College of AgricultureAzad UniversityGarmsarIran

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