Abstract
The effect of temperature on seasonal changes in dry matter productivity in Napiergrass, Pennisetum purpureum SCHUMACH, cv. Merkeron, was investigated among tillers under two different altitude locations in Miyazaki prefecture. At Kitagawa, 640 m above the sea level, crop growth rate per plant was lower in June, while it increased noticeably in July to be higher through September than that at Miyazaki, 10 m above the sea level. This shows the compensatory growth at Kitagawa in the higher temperature condition in July due to the increase of net assimilation rate (NAR) and leaf area index. This increase in NAR of whole plant at Kitagawa was due to the increase in NAR of primary tillers in July and of secondary tillers in August and September. The variation of dry weights (tiller DWs) among tillers increased with the growing days at Miyazaki, especially so in primary tillers. The variation of tiller lengths among tillers was smaller than that of dry weights. In August and September, the less the tiller DWs, the larger were the NARs of individual tillers at Kitagawa, while the situation was reversed at Miyazaki. At Kitagawa where the growing temperature was lower, the variation of the NARs among tillers was smaller than that at Miyazaki and the NARs increased as the tiller DWs decreased, resulting in the higher NAR per plant during the later growth stage.
