Effect of water stress on ten forage grasses native or introduced to Iran

Water stress is one of the most limiting factors in crop and forage production in semi-arid and arid regions. In a greenhouse experiment, ten forage grass species native or introduced to Iran were tested under imposed water stress. The experiment followed a 10 (species) x 3 (soil moisture) factorial design in four randomized blocks. The grass species were desert wheatgrass (Agropyron desertorum [Fisch] Schult.), tall wheatgrass (A. elongatum Host Beavu.), smooth bromegrass (Bromus inermis Leyss.), orchardgrass (Dactylis glomerata L.), June wildrye (Elymus junceus Fisch.), tall fescue (Festuca arundinacea Schreb.), perennial ryegrass (Lolium prenne L.), blue panicum (Panicum antidotale Retz.), large canarygrass (Phalaris tuberosa L.) and mountain wildrye (Secale montaneum Guss.). These species were grown in pots at three levels of moisture (23% [control], 17% [moderate] and 14% [severe] on the dry soil weight basis). Increased water stress decreased total water use in all grass species and tended to decrease plant height, leaf water potential, leaf area, water-use efficiency and root dry weight in all or most species, with varying degrees of reduction among the species. On the contrary, water stress generally had no effects on the root : shoot ratio of the grasses. Based on the reduction in total dry matter production under the two stress levels, tall wheatgrass and smooth bromegrass were the most drought-tolerant species, while orchardgrass was the most susceptible species.