Abstract
The influence of temperature on net assimilation rate (NAR) and leaf weight ratio (LWR) was investigated in 8 tropical grasses, 6 temperate grasses and one arctic grass. Details of the selected temperature regimes and of the species investigated were given in the previous paper of this series. 1. High light intensity increased the NAR in Paspalum dilatatum to a maximum value of 0.77g/g/day at the 36/31℃ temperature regime compared with 0.55g/g/day when light intensities were 0.558 and 0.340gcal/cm^2/day, respectively. The LWR response was in marked contrast to that of the NAR and was markedly higher at low light intensities. 2. The NAR of tropical grasses increased greatly with a rise of temperature from 15/10 to 27/22℃, while it was nearly constant at the level of 0.7g/g/day with higher temperature regimes. LWR of those grasses exhibited greater variation between species but tended to greater values at the highest and the lowest temperatures employed in the experiments. Setaria sphacelata and Cenchrus ciliaris had a high LWR and a markedly lower NAR at 15/10℃ compared to the other tropical grasses indicating that those grasses might be less tolerant of low temperature conditions. 3. The NAR of temperate grasses was nearly constant in a wide range of temperature, from 15/10 to 30/25℃, but decreased at 36/31℃. The NAR of Trisetum spicatum and Poa pratensis decreased above 27/22℃ and it was observed that these two grasses did not tolerate high temperature. The LWR increased at 36/31℃ more markedly in the temperate grasses in which the NAR decreased severely at this temperature. 4. It appears that the tropical grasses which can adapt to low temperature conditions are those having high NAR and low LWR under low temperature and that the temperate grasses which can adapt to high temperature conditions are those having high NAR and low LWR under high temperature. Paspalum dilatatum and Stipa hyalina show the greatest tolerance of low and high temperatures, respectively. 5. Values of NAR were closely correlated with RGR values and the importance of NAR for growth was confirmed. On the other hand, LWR values showed a strongly negative correlation with RGR values.
