RESPONSE OF 3 ARID ZONE GRASSES TO SALT AND WATERLOGGING

In most arid and semiarid regions, the combination of salinity and waterlogging is a dual problem. The combined effects of excess salt and oxygen shortage are potentially highly damaging. In order to assess whether toxic effects of salts are exacerbated under oxygen-deficient conditions, 8-week-old plants of 3 arid zone grass species, Leptochloa fusca (L.) Kunth., Cynodon dactylon (L.) Pers., and Panicum turgidum Forssk., were exposed to NaCl, waterlogging, or NaCl + waterlogging for 5 weeks in greenhouse conditions. There were no significant effects of these stresses on the biomass production of L. fusca, whereas an inhibitory effect of salt and of salt + waterlogging was observed on C. dactylon. The growth of P. turgidum was severely inhibited by all three stresses. A marked inhibitory effect of the combination of salinity + waterlogging was observed on P. turgidum and also on C. dactylon. Leptochloa fusca accumulated significantly higher amounts of Na+, Cl-, K+, and Ca2+ in its shoots compared with the other species, and its leaf osmotic potential was the lowest elf the three species. Accumulation of Na+ and Cl- in the shoots of C. dactylon was higher in saline waterlogged conditions than in saline conditions, and the reverse was true for shoot K+. By contrast, in L. fusca, accumulation of Ca2+ and K+ in the shoots was less under saline + waterlogged conditions than in saline conditions. Panicum turgidum had relatively high stomatal diffusive resistance. Waterlogging exacerbated the effect of salt on P. turgidum and C. dactylon but not on L. fusca.