The pericarp structure and histogenesis in Enkianthus: on the ancestral fruit type in Ericaceae family.

This article focuses on the anatomical structure and development of the fruit pericarp in the genus Enkianthus, the sole genus of the monotypic subfamily Enkianthoideae within the family Ericaceae sensu lato (s.l.). The study reveals that Enkianthus fruits are superior loculicidal capsules differentiated into three histogenetic zones: a one-layered exocarp, a multilayered mesocarp with peripheral parenchymatous and inner sclerenchymatous zones, and a one-layered endocarp of tangentially elongated sclereids. These fruits correspond to the Hamamelis-type capsule, considered the probable ancestral (plesiomorphic) fruit type for Ericaceae and related families, from which other fruit types such as septicidal capsules, pyrenariums, and berries have evolved. Comparative analysis among Enkianthus species indicates evolutionary trends involving reduction and specialization of pericarp layers, supporting phylogenetic data that position Enkianthus as basal within Ericaceae. The findings contribute to understanding fruit morphogenesis and evolutionary pathways in Ericaceae and related Ericales families.