Effects of sodium sulfate and sodium bicarbonate on the growth, gas exchange and mineral composition of lettuce

• Published in: Scientia horticulturae 2004, Vol.99 (3), p.215-224
• Main Authors: Bie, Zhilong, Ito, Tadashi, Shinohara, Yutaka
• Format: Article
• Language: English
• Subjects: Agronomy. Soil science and plant productions; Biological and medical sciences; Fundamental and applied biological sciences. Psychology; Gas exchange; Lactuca sativa L; Mineral composition; Salinity
• ISSN: 0304-4238; 1879-1018
• DOI: 10.1016/S0304-4238(03)00106-7

The responses of two butterhead lettuce ( Lactuca sativa L.) cultivars ‘P’ and ‘L-2’ were investigated under Na 2SO 4 and NaHCO 3 salinity stress. The influences of salinity on gas exchange and distribution of mineral composition in plants were determined. The salinity treatments were applied through a nutrient solution containing 0, 20, 40 and 60 mM Na 2SO 4 or 0, 2.5, 5 and 7.5 mM NaHCO 3. With increasing concentration of Na 2SO 4 or NaHCO 3, leaf area, shoot dry weight, leaf length and leaf width decreased, photosynthetic rate and stomatal conductance also diminished. NaHCO 3 was more toxic to lettuce shoot growth than Na 2SO 4. The decrease in water uptake per plant implied osmotic stress existed under Na 2SO 4 salinity, while in the NaHCO 3 experiment, water uptake was not affected but pH of the nutrient solution increased markedly. Leaf necrosis appeared in both cultivars at Na 2SO 4 concentrations above 40 mM, and leaves were chlorotic at NaHCO 3 concentrations above 5 mM. In both experiments, leaf injury symptoms were more severe in ‘L-2’ plants than in ‘P’ plants. The concentrations of K and Ca decreased, whereas Na concentration increased, as Na 2SO 4 concentration increased. The Na concentration in the root was greater than in the shoot of ‘P’ plants, whereas the trend was just the reverse in ‘L-2’ plants. The K concentration in the shoot decreased and Na concentration increased with increasing NaHCO 3 concentration. Shoot Ca only decreased in ‘L-2’ plants. The growth reduction under Na 2SO 4 stress may be due to the combined effects of osmotic stress and excess accumulation of Na, while in the NaHCO 3 experiment, the growth reduction may be related to the HCO 3 − toxicity and high pH rather than water stress or excessive Na. The cultivar ‘L-2’ was more sensitive to Na 2SO 4 and NaHCO 3 salinity than the cultivar ‘P’.