Effect of temperature and solar radiation on the development of dry matter and attributes of elephant grass (Pennisetum purpureum Schum.)

Nineteen accessions of elephant grass (Penniseturn purpureurn) were grown in a long-day photoperiod at 5/10, 18/13, 21/16, 27/22, 33/28 and 36/3l�C day/night temperatures during spring, summer and autumn in the Canberra phytotron. The temperature optimum for dry matter production was 33/28�C, and the magnitude of dry matter production was dependent on the solar radiation received; the low radiation levels in autumn reduced yields of advanced plants. Except at the lowest temperature, cumulative yield was associated with cumulative radiation. Rate of stem elongation was highest at 33/28�C under the spring and summer radiation regimes. Under autumn radiation conditions, rate of elongation was highest at 27/22�C. Rate of leaf appearance and leaf area per plant were linearly related to temperature and were little affected by radiation level. Rate of tiller production showed two maxima, at 18/13-21/16�C and at 33/28-36/31�C, and the maximum temperature was dependent on radiation level. The accessions Q5083, Bana grass and Taiwan consistently produced high yields throughout the range of temperatures tested. The results are discussed in relation to accession performance in the field.