Comparative Responses of Glaucium spp. to Salinity Stress

Salinity is considered a major factor that reduces plant growth in arid and semiarid regions where soil salinity is naturally high and precipitation is insufficient to achieve proper leaching.  Horned Poppies (Glaucium spp.) are members of the Poppy family, Papaveraceae and are native to  the Mediterranean and Middle East where they are considered to be somewhat salt tolerant. The objectives of this study were to: 1) evaluate the comparative salinity tolerance of Horned Poppy species 2) examine the effects of salinity on plant characteristic associated with aesthetics of the species; and 3) determine tolerance mechanisms associated with superior salinity tolerance among species. With increased salinity levels from the control (tap water) to EC levels of 5, 15, and 25 dS m-, leaf color declined over time to unacceptable ratings (below 6). In G.flavum, leaf color was least affected  while all other species declined to unacceptable ratings of 5.3 (G. acutidentatum), 4 (G. grandiflorun), and 3.2 (G. corniculatum at the salinity level of 25 dS m-1. Leaf area decreased linearly in all species with increasing salinity.  G.flavum maintained the greatest leaf area at all salinity levels.  In G. flavum, as salinity levels increased from control to 5, 15 and 25 dS m-1, average total nonstructural carbohydrate content (TNC) decreased by 15.7, 28.6 and 43.6% while the average TNC decrease in G. acutidenatum shoots was 17.6, 36.8 and 48%. The decrease in G. grandflorum was 20, 40 and 48.6% while the decrease in G. corniculatum was 28.9, 49, and 53, respectively.  As salinity levels increased from control to 5, 15 and 25 dS m-1, average proline content in shoots increased by 218, 367, and 537% in G. flavum, 64.5, 296 and 510% in G. acutidenatum, 156, 273 and 428% in G. grandflorum, and 79, 188, and 337% in G. corniculatum.  Results indicated that K+/Na+ ratio was ≥ 1 at all salinity levels in G. flavum, as compared to G. acutidenatum, G. grandflorum and G. corniculatum. In conclusion, as salinity increased, Glaucium spp. exhibited a reduction in leaf characteristics, plant height, flowering characteristics, overall plant quality, TNC, and K+/Na+ ratio, and increased shoot total reducing sugars and proline content. G. flavum showed higher salinity tolerance at all salinity levels as compared to the other species. Proline accumulation likely added to the salinity tolerance through osmoregulation or by acting as a carbon and nitrogen sink for stress recovery.