Morphogenetic and structural characteristics of field-grown timothy cultivars differing in maturity

The leaf area development of grasses and, subsequently, radiation interception depends on morphogenetic processes such as leaf extension and appearance. No detailed studies of leaf extension and appearance of field-grown timothy (Phleum pratense L.) cultivars differing in maturity have been reported in the literature. Leaf extension and appearance of field-grown timothy cultivars differing in maturity and their impact on sward structural characteristics such as leaf size per tiller and tiller density were studied during primary growth in the spring of 1991 and 1992. The leaf extension rate of early-maturing cultivars was greater than that of late-maturing cultivars during primary growth of timothy. There were no differences in leaf appearance rates among cultivars. Hence, individual tillers of early-maturing cultivars developed a larger leaf size than late-maturing cultivars. In 1992, late-maturing cultivars had a greater tiller density than early-maturing cultivars which compensated for the smaller leaf size. Different tiller density-tiller size characteristics of early and late-maturing timothy cultivars resulted in a similar outcome in terms of LAI.