A new morphogenetic type of fruit for Hamamelidaceae: the case of Loropetalum

Abstract

Abstract With the current reassessment of the phylogeny of Hamamelidaceae, the problem of revealing the apomorphies and plesiomorphies in this group arises and peculiarities of histogenesis of the reproductive structures deserve recognition. With the aim to fill in the gap in the data on fruit structure in Hamamelidaceae, we focused on investigating the processes of fruit organogenesis and histogenesis of the fruit wall in Loropetalum. The fruit of L. chinense is an almost inferior dimerous syncarpous loculicidal (dorsoventrally dehiscent) capsule with the mature fruit wall differentiated into epicarp, mesocarp and endocarp. The main tissue of the epicarp and the peripheral zone of the mesocarp are composed of thin-walled cells with scattered brachysclereids, whereas the inner zone of the mesocarp consists of fibre-like sclereids. The endocarp finishes its differentiation at the young fruit stage and is represented in mature fruit by several layers of thin-walled cells. The fruit of L. chinense represents capsules of the Forsythia type, which have not been previously described for Hamamelidaceae, and it differs from capsules of the Hamamelis type described for Hamamelis, Corylopsis and Fothergilla. The revealed characters of L. chinense fruits indicate the possibility of transformation of the explosive capsule into a pyrenarium.