Effect of different quality irrigation water on the growth, mineral concentration and physiological parameters of viburnum tinus plants

Treated wastewater may be considered an alternative source of water and fertilizer nutrients for landscape plants. However, NaCl, the principal compound in this water, can be detrimental to plants. Viburnum tinus plants were submitted for 4 months to 4 irrigation treatments from different sources: control (Control) (EC <0.9 dS m-1); NaCl solution (NaCl) (EC = 4 dS m-1); irrigation water normally used in the area (IW) (EC = 1.2-1.8 dS m-1) and reclaimed water (RW) (EC = 4 dS m-1). During a recovery period of two months, all plants were irrigated with the control water. The results showed that both leaf area, plant height and biomass were different among plants of NaCl, IW and RW treatments, and decreased at the end of the saline period. These changes were more pronounced in the NaCl treatment. The growth alterations evident after the recovery period indicate that salts continued to be present in the substrate. Compared with the control, NaCl and RW plants showed a greater rate of Na+ and Cl- Absorption by roots. Stem water potential was mainly affected by the NaCl treatment, which was the only treatment that did not recover their stomatal conductance and photosynthesis rate values at the end of the experiment. Plants of the IW treatment showed slight changes in gas exchange with respect to the control. Hence, using different sources of water with similar EC, it is important to know the exact composition, since the toxic effects produced by high concentrations of Na+ and Cl- might be offset by the effect of other ions like magnesium, potassium and phosphorus. In the physicochemical analysis of water, the highest concentrations of these ions were observed in RW and as consequence, their concentrations in plants were not reduced by the Na+ and Cl- effect; phosphorus even increased, improving the plant nutritional balance.