The flowering of sesame (Sesamum indicum L.) in response to temperature and photoperiod

Abstract

Sesame (Sesamum indicum L.) is reported to be a quantitative short day plant in its flowering response. The cultivars Aceitera and Hnan Dun were able to respond to short days as early as the cotyledonary stage, and only one 8 h photoperiod was necessary at this stage for flowering to be accelerated above the 15 h photoperiod control. To see whether geographic origins of cultivars would influence their response to photoperiod, the flowering responses to 8, 13 and 15 h photoperiods among 20 varieties were analysed using cluster analyses. The groupings were consistent enough to suggest a broad relationship between geographic origins of the cultivars and response to photoperiod, but there were several exceptions. There were significant interactions of temperature and photoperiod on the rate of flowering of sesame. However, when the rate of vegetative development (plastochron index of the plant at the time the first floral bud appeared) was used as a covariate in analyses of covariance, significant effects of photoperiod on flowering disappeared. Temperature, however, remained a significant factor. The flowering of some varieties was independent of temperature over the range 20/15 to 30/25¦C; other varieties flowered more rapidly at the higher temperatures. The quantitative short day nature of the flowering of sesame appears to act through the rate of vegetative development but not directly on floral bud induction. Temperature, on the other hand, affects both vegetative development and the rate of floral induction in some varieties.