Screening Glaucium spp. for Drought Resistance with Emphasis on the Contributing Physiological Characters and Overall Performance

With increasing population demands on the world’s water supply, there is a greater need for water conservation, especially in arid and semiarid regions.  Horned Poppies (Glaucium spp) are members of the Poppy family, Papaveraceae, and are native to the Mediterranean and Middle East regions where they are considered somewhat drought tolerant. The objectives of this study were to 1) screen for drought tolerance of the common Horned Poppy species; 2) examine the effects of drought on plant characteristics as related to their aesthetics as well as the mechanisms associated with drought tolerance.  Lysimeter columns were used in this study which was replicated twice. All columns were placed in the Colorado State University Plant Science Greenhouse in Fort Collins, Co.  Fifty seedlings, at the 3 leaf stage, of each species were transplanted, 1 each per PVS tubes (15 cm diameter and 50 cm long) containing commercial potting mix The potting mix was mixed with sand 2:1 to increase pore space. Water regimes applied included control (100% of the total ET, (evapotranspiration)), as well as 75%, 50% and 25% of the total ET. With lower water regimes, leaf color declined over time to unacceptable ratings (below 6) in both G. grandiflorun and G. corniculatum. In G.flavum, and G. acutidentatum, leaf color was not adversely affected under all water regimes. Leaf area decreased linearly in all species with increasing drought. G.flavum maintained the greatest leaf area at all water regimes followed by G. acutidentatum, G. grandiflorum and G. corniculatum.  Increased water stress resulted in fewer flower buds, reduced flower number, and smaller flowers in all species. Also, increasing drought decreased the attractiveness of all Glaucium spp. although at different degrees. G. flavum showed greater transpiration efficiency (TE) since it was able to maintain its ET at lower rates while maintaining higher attractiveness when compared with G. acutidentatum, G.grandiflorum and G. corniculatum, respectively. In summary,as drought increased, Glaucium spp. exhibited reduction in leaf characteristics, plant height, flowering characteristics, overall plant quality (attractiveness), TNC, and ET rate, and increased shoot total reducing sugars and proline content. G. flavum showed higher drought tolerance at all water regimes when compared to the other tested species. Since proline accumulation increased with drought stress it is likely that it aided drought tolerance through osmoregulation or by acting as a carbon and nitrogen sink for stress recovery.