Nitrate uptake, xylem NO3- flux, and nitrate assimilation in cowpea exposed to salinity

Authors

  • Rafael Aragão Universidade Federal do Ceará
  • Joaquim Silveira Universidade Federal do Ceará
  • Evandro Silva Universidade Federal do Ceará
  • Ana Karla Lobo Universidade Federal do Ceará
  • Antônia Dutra Universidade Federal do Ceará

Keywords:

Salt stress, Nitrogen- effects on the plants, Vigna unguiculata, Xylem

Abstract

This work was carried out to evaluate what is the nitrate acquisition stage (nitrate uptake, xylem nitrate flux or assimilatory reduction) most influenced by the presence of NaCl in cowpea. Twelve day-old seedlings were treated with 50 mM of NaCl in nutrient solution during four days and measurements carried out under two contrasting environmental conditions: typical day (full sun) and completely cloudy day (cloudiness). The salinity affected more intensely the xylem sap flux and nitrate flux than transpiration. Plants treated with NaCl showed a strong decrease in both nitrate uptake rate and leaf nitrate reductase activity as in the full sun as in cloudy day. Transpiration was reduced by the cloudiness while xylem sap flux and nitrate flux remained unchanged, in both salt-treated and control. Moreover, nitrate uptake and nitrate reductase activity were less affected by cloudiness than the transpiration. In addition, NaCl negatively affected nitrate accumulation in roots, stems and leaves while the cloudiness affected only the leaf nitrate accumulation, both in control and stressed plants. Salinity affects more negatively the nitrate xylem flux, as compared with the nitrate uptake and nitrate assimilatory reduction in cowpea leaves.

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Published

2010-03-02

Issue

Section

Crop Science