Fruit development in eucalypts (Myrtaceae: Eucalypteae)

Abstract

Developmental anatomy of eucalypt flower buds from flower to mature fruits was investigated using light microscopy. Several important features contribute to the maturity of flower and fruit. The epidermis of the flower in many species is replaced by periderm in the fruit. Brachysclereid idioblasts develop in the parenchymatous zone beneath the epidermis; fibres develop from cambium-like activity in the vascular bundles located in the mid-region of the ovary wall; and cells adjacent to the locule lining mature as transversely oriented filiform sclereids. The initiation of these features in relation to anthesis varies among taxa, and this influences flower and fruit anatomy and morphology. In taxa where sclereids and fibres are initiated following anthesis, there is substantial post-anthesis growth and fruits are larger than flowers. When these features are developed before anthesis, the flowers are essentially pre-fruits that exhibit little or no further growth in the fruit stage apart from additional cell-wall lignification. Several other anatomical features, such as oil ducts and the distribution of oil glands and crystal layers, are not developmentally variable, but are phylogenetically informative within the eucalypt group.