Growth analysis of timothy cultivars differing in maturity

Abstract

The delay in ear emergence or heading between early and late-maturing timothy (Phleum pratense L.) cultivars can be up to 3 wk. The objective of this study was to determine the relative importance of radiation interception and radiation-use efficiency in the differences in shoot growth between early and late-maturing timothy cultivars. During the primary growth in 1991 and 1992, four timothy cultivars differing in maturity were compared for shoot growth, leaf area development, radiation interception and radiation-use efficiency using weekly samplings. Stem elongation of early-maturing cultivars progressed faster than that of late-maturing cultivars. Early-maturing cultivars had greater shoot growth and RUE than late-maturing cultivars. Differences in cumulative intercepted PAR among cultivars were relatively small compared with cultivar differences in RUE. Hence, the greater shoot growth of early-maturing cultivars compared with that of late-maturing cultivars was attributed to a greater RUE of the early-maturing cultivars. Consequently, different values of RUE should be used for early and late-maturing timothy cultivars in crop models based on efficiencies of radiation interception and utilization. Key words:Phleum pratense L., cultivars, growth, radiation, photosynthesis