Altitudinal effects on Stylosanthes guianensis at a low latitude site: 1. Flowering

Five selections of Stylosanthes guianensis var. guianensis with a short-day flowering response were grown at three sites at altitudes of 10, 280 and 1000 m on the island of Bali, Indonesia at latitude ca. 8 30’ S. Mean site temperature was ca. 6 C lower at the highest site whilst mean short-wave radiation was lowest at the intermediate site.Date of 50 % floral initiation (FI) varied from 1 February to 21 June, when daylength (sunrise to sunset plus half civil twilight) deereased from 12.85 to 12.00 h. FI was independent of site for cv. Graham and cv. Cook, but at 1000 m it was 14 and 77 days earlier for cv. Endeavour and cv. Schofield respectively relative to the 280 m site. Little flowering of cv. Schofield occurred at 10 m, and it is suggested that cool temperatures promoted an increase in the critical photoperiod for this cultivar, or that warm temperatures inhibited flowering. FI was delayed at 1000 m in CPI 34906.The duration of the phase from FI to flower appearance (FA) varied from 29 to 75 days according to selection and to site, and was negatively related to mean temperature, radiation, and maximum temperature for cv. Graham, cv. Cook, and CPI 34906 (but not for cv. Endeavour). Number of nodes at FA in this determinate species generally reflected growing conditions in the pre-flowering phase and was positively associated with age at FA in plants of particular varieties. Present address: School of Agriculture, Hawkesbury Agricultural College, Richmond, 2753, NSW, Australia.We are indebted to Universitas Udayana, Bali, Dinas Peternakan (Propinsi Bali), Penelitian Proyek Peternakan di Bali (P3B) and to the Australian Universities International Development Program for support and for facilities, to Dr I. B. Oka, Professor I. M. Nitis, Ir I. K. Rika, Drh I. B. Arka, Ir P. Sastrawan and Ir M. Oka for cooperation and assistance, and to Mrs K. Basford, Mr I. F. Horton andMr J. Benders for help with data treatment