The influence of photoperiod on head formation in some Brachiaria species and Chloris gayana cv. Masaba.

Abstract

The effect of the photoperiod on head formation was investigated in 5 Brachiaria spp. and selected ecotypes of C. gayana cv. Masaba. The experiments were conducted in the glasshouse with photoperiods of 10, 12 or 14 h in 1971 and 9, 10.25 or 12.5 h in 1973. The photoperiods comprised 9 h natural daylight in the summer, supplemented with 40 W incandescent lamps. It was concluded that B. mutica is a qualitative (obligate) short-day plant whereas B. ruziziensis and cv. Masaba are quantitative short-day plants. B. brizantha and B. decumbens were already flowering when exposed to 24-h photoperiods during the pre-experimental period in 1971. In Brachiaria introduction PI 299498, head formation in both experiments occurred a few days earlier under the short photoperiod treatment. In the later-formed heads of all grasses tested the number of racemes/head decreased, though the length of the racemes was not affected. During the 1971 experiment, culm branching was observed in most of the grasses. It was found that in Masaba "secondary" culms were mainly formed during photoperiods of 10 and 12 h but rarely in 14 h. "Tertiary" culms in B. ruziziensis were observed in photoperiods of 10 and 12 h. It is suggested that culm branching can be attributed to high RH. The low seed production of tropical grasses is mainly caused by the low number of heading tillers/unit area and the disynchronization of the flowering resulting from the long period of head production. It is suggested that more research on the photoperiodic response of these grasses would provide useful information on seed production. After selection of photosensitive cv. and seed production at lat. of approx. 15 deg N. and 15 deg S. the long period of heading would be reduced and the synchronization of the flowering would be improved. Some of the early heading types of Masaba are typical examples of photosensitive cv. (Abstract retrieved from CAB Abstracts by CABI’s permission)