Physiological Responses of Tomato Plants to the Combined Effect of Root Hypoxia And NaCl-Salinity

Abstract

Flooding and salinity are important environmental factors restricting plant growth and productivity throughout the world because these two stresses frequently coexist. The objective in this work was to investigate the interactive effects of salinity and hypoxia on the physiological responses of tomato (Solanum lycopersicum L.) plants. To this end, growth, photosynthesis, stomatal conductance and organic solute accumulation was determined in hydroponically grown plants exposed for 4 weeks to hypoxia, salinity (100 mM) or to the combination of salinity and hypoxia.  Obtained results showed that plants exposed to salinity, either alone or in combination to hypoxia showed decreased root and shoot biomass production. However, root and shoot water contents were decreased only for plants exposed to the combination of the two stresses.  Concomitantly, leaf area, leaf mass per area, and K⁺ and sugar contents were significantly decreased in comparison with control (normoxia, 0 mM NaCl) plants. Na⁺ and proline significantly accumulated in roots and leaves of plants exposed to salinity, either alone or in combination to hypoxia. Taken together, these results suggest that tomato plants are strongly sensitive to the combination of hypoxia and salinity stresses. This is most probably due to a low K⁺-uptake selectivity, a strong Na⁺ absorption, and the disturbance of K⁺ translocation towards shoots and the loss of its use efficiency for biomass production.

Key words: Tomato, hypoxia, salinity, growth, ions, solute accumulation

Faouzi Horchani et al. Physiological Responses of Tomato Plants to the Combined Effect of Root Hypoxia And NaCl-Salinity. J Phytol 2/11 (2010) 36-46