Structure of Mahogany (Swietenia macrophylla King) fruit, seed and their characteristics

Abstract

The fruit is a large (12.90–15.40 cm length x 8.74–10.64 cm diameter, excluding the capsule stalk), erect woody capsule. There are five outer thick and five inner thin valves. There is a central axis, the columella, which is typically 5-angled to which the seeds are attached pendulously by their wings. The mean weight of a capsule was 369.47 (± 54.01) g, ranging between 231.13 (± 25.67) g and 565.55 (± 72.82) g. On average a capsule contains 43 germinable seeds. One thousand fresh seeds (with wings) weigh from 607.06 g to 919.15 g. Significant differences existed between locality. Capsules collected from Karulai were found to be larger in size when compared to those collected from other localities. Seeds are winged and dark brown coloured. Longitudinal section of a seed revealed that the seed consists of a minute embryo embedded peripherally at one side within the massive cotyledons which is surrounded by a white thin testa which is again covered by dark brown coloured spongy tail-like wing. The variation in seed weight, germination percentage and germination period could be due to provenance differences, size of capsules, crown size of parent trees, level of seed maturity, site fertility, health condition of parent trees and environmental factors of a locality. The selection of parent trees having larger capsules appears to be most promising for seed collection.