Effects of Light Intensity on Reproduction in S.48 Timothy (Phleum pratense L.)

Abstract

IN recent years the role of light intensity as a major factor controlling growth of herbage in the sward has been emphasized. The production of inflorescences in herbage grasses also appears to be influenced by light intensity in conditions otherwise known to favour the onset of floral initiation. Several investigators^1–3 have remarked on the reduced flowering obtained in the glasshouse in winter, when photoperiod and temperature are artificially maintained at summer-levels. Experiments in the glasshouse have shown that inflorescence production in S.48 timothy occurs readily in the spring and early summer, whereas floral initiation is sporadic and delayed when plants are exposed to similar photoperiods and temperatures in the autumn and winter. In an attempt to separate the effect of light intensity, which presumably exerts an indirect effect on flowering by influencing photosynthesis, from that of factors such as photoperiod, which have a direct effect on flowering, an experiment was conducted in summer to test the effect of reducing the natural light intensity on the reproduction of S.48 timothy.