Floral Maturation Indices of African Yam Bean (Sphenostylis stenocarpa Hochst Ex. A. Rich) Harms (Fabaceae)

Abstract

The present investigation aimed at understanding the floral morphology and maturation indices of African yam bean (AYB), knowledge of which is very relevant for the crop’s improvement programs. Ten accessions of AYB were grown in rows of ten plants, in three replications. Thirty anthesized flowers were collected from each accession for the study of the floral parts. The progressive development of flowers from buds was additionally investigated. AYB flower is large and complete. The calyx was fused and the corolla has five petals (one standard, two wings and two keels). AYB accessions exhibited racemes and indeterminate form of inflorescence. The mean standard petal length and width were 2.94 cm and 3.59 cm respectively. The androecium which surrounded the carpel consists of ten filaments (nine fused, one free). The gynoecium comprised flattened stigma with hairy edge. The mean length of style and ovary was 1.60 cm and 1.00 cm respectively. A distinct purple line (along the enclosing end of the standard petals) became visible at flower bud stage, when bud length reached 2.2 cm - 2.7 cm. Anthesis occurred within 24 hours beyond this stage and petals dropped a day after anthesis. Certification of stigmatic receptivity and pollen fertility may be dependent on the above information. The present study further provides basis for the understanding of pollination mechanism and breeding system within the species.

Keywords

• androecium
• anthesis
• floral morphology
• flower bud
• gynoecium