Growth responses and ion regulation of four warm season turfgrasses to long-term salinity stress

Increased need for salinity tolerant turfgrasses continues due to increased use of saline water for lawn irrigation and turfgrass establishment on highly saline soil in arid and seashore regions. Turfgrasses growing on saline soil suffer from long-term salinity stress, so this experiment was conducted to study the salinity tolerance, growth, and physiological responses of four warm season turfgrasses [including ‘Diamond’ zoysiagrass (Zoysia matrella (L.) Merr.), ‘Z080’ zoysiagrass (Z. japonica Steud.), ‘C291’ bermudagrass (Cynodon dactylon (L.) Pers), and ‘Adalayd’ seashore paspalum (Paspalum vaginatum Sw.)] to 9 months of salinity stress. Seven salinity levels of irrigation water (0, 90, 180, 360, 540, 720, and 900 mM NaCl) were applied to turfgrasses grown in plastic tubes in a glass room. The salinity tolerance decreased in the following order according to percent green leaf canopy area after 9 months of salinity treatments: ‘Diamond’ > ‘Adalayd’ > ‘C291’ > ‘Z080’. Leaf weight, leaf length, canopy height, shoot density were significantly affected by salinity treatments for all turfgrasses. However, leaf width and/or leaf number per shoot were not affected by salinity in all turfgrasses except ‘Diamond’. Leaf and/or root water contents were also little affected. As salinity increased, leaf and root Na+ concentrations and Na+/K+ rates increased significantly and K+ concentrations decreased significantly except that of ‘Adalayd’ leaf. ‘Diamond’ and ‘Z080’ could reduce Na+ accumulation in the leaves by salt secretion from salt glands, while ‘Adalayd’ could exclude Na+ from the leaves and accumulate K+ in the leaves. ‘C291’ exhibited both ion regulation mechanisms, but to much less extent. Different growth responses and ion regulation means of four turfgrasses reflected different salinity tolerance mechanisms.