THE EFFECT OF TEMPERATURE AND PHOTOPERIOD ON INFLORESCENCE DEVELOPMENT IN STRAINS OF TIMOTHY (<i>PHLEUM</i> SPP.)

Abstract

A study has been made of the flowering requirements, for temperature and photoperiod, of a range of timothy strains, including American, British and Scandinavian material. All the strains tested are long‐day in their photoperiodic responses, and there is no “winter requirement” for low temperature (0–5°C.) or short days before flowering. There is, however, an inhibitory effect of high temperature in the greenhouse on flower formation, lf the temperature is too high, no heads are produced, although photoperiod may be adequate. Instead elongated indeterminate shoots are formed which often become stoloniferous. The effect of high temperature varies with the strain, and appears to be related to the May temperature of the region of origin. Under greenhouse temperatures of 55–65°F. American and Canadian commercial strains show little inhibition of flowering, but many plants of the Scandinavian strains fail to produce heads. The British hay strains show intermediate heading behaviour, but only an occasional plant of the diploid S.50 formed heads under these conditions.