Photoperiod and temperature effects on the flowering of Stylosanthes guyanensis

Abstract

Selections of Stylosanthes guyanensis were grown in controlled environment cabinets at 27¦ and 20¦C and exposed to differing photoperiods. All selections showed a short-day flowering response, the apparent critical photoperiod varying from about 13 hours in CPI 40255 to about 11.5 hours in cv. Schofield. The 20¦ treatment promoted flowering in longer photoperiods in CPI 40255 and cv. Schofield and almost prevented flowering in CPI 34906 and cv. Cook. CPI 33706 did not flower at 27¦C. Flowering response was not related simply to latitude or altitude of selection origin. Removal of mature leaves hastened flowering. The same selections grown in the field at Mt. Cotton, south-east Queensland (lat. 27¦37'S) reached floral initiation at dates varying from February 5 to April 20. The duration of the period of floral initiation to flower appearance was negatively associated with daily maximum temperature. The range of first flowering dates within a selection varied from 8 to 78 days.