The Leaf Growth of Trifolium Repens as Influenced by Seasonal Changes in the Light Environment

Abstract

The changes occurring in the development and growth of the leaf canopy of undisturbed T. repens stands were followed throughout a complete year. Marked seasonal changes in the amounts of leaf present in the stands in various stages of development and senescence, and in the amounts and heights from ground level of leaf above the 95% light interception level, were recorded. The lowest values occurred in the winter and the highest in the late spring. Within the limits of growth set by temperature and moisture supply, and excluding rate processes determined by temperatures, changes in the growth processes involved in the development of the leaf canopy were largely dependent on changes in the light environment. Additionally, at all times an equilibrium was maintained between the light environment and leaf growth such that virtually all light was continually intercepted by actively photosynthesizing leaf. The maintenance of this equilibrium was associated with differences in the rates of initiation and senescence of leaves, in the number of leaves present per unit area and in the maximum dimensions attained by the various parts of the leaves, factors which were markedly influenced by changes in season and weather. The results are discussed in terms of dry matter accumulation and the yield potential of grassland plant communities. The significance of this on calculations made for the efficiency of energy conversion of such communities is also discussed.