DIFFERENTIAL WATERLOGGING TOLERANCE IN 3 GRASSES OF CONTRASTING HABITATS - AELUROPUS-LAGOPOIDES (L) TRIN, CYNODON-DACTYLON (L) PERS AND LEPTOCHLOA-FUSCA (L) KUNTH

High concentrations of reduced iron and manganese, developed as a result of anoxia in waterlogged soils, cause considerable growth inhibition in many plant species. In order to determine the effect of waterlogging on three grass species, Aeluropus lagopoides (L.) Trin., Cynodon dactylon (L.) Pers. and Leptochloa fusca (L.) Kunth., particularly in relation to iron and manganese, they were subjected to three waterlogging treatments: unflooded (control), intermittent and continuous waterlogging for 6 weeks in a greenhouse. Waterlogging had an adverse effect on the growth of A. lagopoides and C. dactylon. Leptochloa fusca produced significantly more dry biomass and had a lower water potential than the other two species under waterlogged conditions. Waterlogging treatments caused a marked but comparable reduction in chlorophyll content in all three species. Shoot iron and manganese contents increased in all three species with increasing waterlogging, but least in L. fusca which had the ability to accumulate relatively more iron and manganese in or on its roots. A. lagopoides and C. dactylon contained more than 2000-mu-g/g iron in the shoots, a concentration reported as toxic in most plants. Root iron and manganese contents increased more in L. fusca than in the other two species, showing immobilization in or on the roots. Leptochloa fusca was relatively most tolerant, A. lagopoides intermediate, and C. dactylon most sensitive to waterlogging. The tolerance of L. fusca to waterlogging was related to its better ability to control the uptake of iron and manganese to the shoots.