Volume 39, 160-170

Tropical Grasslands (2005) Volume 39,160–170

Flood tolerance of Panicum decompositum: Effects on seedling biomass

C.J. GEURTS¹, J.E.D. FOX^1,2, T.M. LUONG² AND M.C. COX²

¹Department of Environmental Biology
²Mulga Research Centre, Curtin University of Technology, Perth, Western Australia, Australia

Abstract

Panicum decompositum is a perennial, buttforming grass that occurs in the Fortescue Valley floodplain in the Pilbara region of Western Australia, and is grazed by cattle. Summer rainfall and flooding appear to influence pasture availability by affecting plant growth and numbers. In a pot study, P. decompositum seedlings were transplanted and grown for 63 days to examine effects of varied flooding duration on biomass, in the absence of grazing. One week after transplanting, 1 set was flooded for 1 week; after 2 weeks, 1 set was flooded for 2 weeks and another for 4 weeks; another set was flooded for 1 week after 6-weeks’ growth; and a control set was not flooded. No seedling mortalities occurred during the trial. While flooding reduced seedling growth and shoot:root ratios, most plant attributes were not significantly affected by flooding. Effects were reduced when seedlings were older at inundation. Flooded plants developed elongated aerenchyma cells (48 × 118 µm) in the root cortex, whereas non-flooded plants had smaller, cuboid parenchyma cells (61 × 81 µm), indicating that P. decompositum has some intrinsic tolerance of flooded conditions.