Physiological Responses of Swiss Chard to Salinity Stress

Swiss chard (Beta vulgaris L. subsp. cicla) is widely cultivated in the world as a green vegetable. The objective of this study was to investigate the effects of different levels of saline water (S1 (control condition) =0.6, S2=7, S3=14 and S4=21 dS m-1) on some physiological characteristics of Swiss chard. Swiss chard plants were grown in a controlled-environment greenhouse. At the end of the growth stage, dry matter, titrable acidity (TA), total soluble solids (TSS), pH, crop evapotranspiration (ETc) and proline were measured and evaluated. Results showed that as salinity increased, dry matter decreased but TA increased. Results also revealed that as salinity increased the pH and ET reduced significantly and caused reduction in photosynthetic activity and growth. TSS and proline increased significantly at 1% level of probability. Comparison of means showed that the highest levels of TA and TSS were 0.38% and 7.25% in treatment S4, respectively. Most proline with an average of 15.55 (µmol g-1) was observed in S4. Results revealed that increasing salinity from 0.6 to 21 dS m-1 the pH values reduced from 6.28 in control treatment to 5.8 dS m-1 in S4. The maximum ETC (3.33 mm day-1) was occurred in treatment S1. In general, the amount of dry matter was reduced about 21% in S2 compared to the control treatment, although the rate of reduction in dry matter was more in the rest of treatments. It is concluded that among the different water salinity levels, the optimum yield can be achieved in S2 treatment.