Distribution of Hymenachne acutigluma (Steudel) Guilliland in ponded pasture is limited by photosynthetic response to temperature

Abstract

Hymenachne amplexicaulis, an exotic grass established in ponded pasture in Central Queensland has the potential to become a weed. A suggested alternative, the native grass H. acutigluma produced little biomass when flooded. This investigation attempted to identify limitations to the growth of H. acutigluma under flooded conditions.

A series of experiments compared the characteristics conferring adaptation to flooding of H. acutigluma with those of H. amplexicaulis. Photosynthetic activity of the 2 Hymenachne spp. was compared in response to light and temperature. The distribution of resources in response to reduced photosynthesis and flooding was also determined.

When flooded, H. acutigluma had similar structural adaptations to H. amplexicaulis. However, H. acutigluma had a lower photosynthetic rate at reduced temperatures and the photosynthetic leaf area decreased when flooded. The implications of these findings are discussed in terms of limitations to the distribution and productivity of H. acutigluma in ponded pasture.