Studies in the Physiology of Flowering of Timothy (Phleum pratense L.)

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Abstract
The main-stem ear lengths of S. 48 timothy plants increased with shoot age at the time of flowering, reaching a peak after the expansion of 20–25 leaves and then declining again: similar responses were also apparent in subsidiary tillers on the same plants. In natural conditions, the maximum ear lengths were attained on shoots originating in autumn and early winter and flowering the following summer; shoots arising later developed progressively shorter ears. It is suggested that the potential ear length attainable on a shoot is linked with the size of the shoot apex built up during vegetative development. In early formed tillers, mainly primary and secondary, a reduced nitrogen supply decreased the size of ears by limiting spike differentiation. The intensity of the nitrogen effect increased in later generations of tillers, with the result that the influence of shoot age on ear length became obscured. The results emphasized the importance of the internal relations between tillers in perennial plants, especially with regard to mineral nutrition.