Zornia latifolia (Leguminosae), an unusual seedling functional type from northern South American savannas

Abstract

Seedling functional types have been studied at lower intensity in savanna forbs because most studies are biased toward woody species in forests. In this study, we investigated the seedling morphology and early morphological development of the basal bud bank structures of Zornia latifolia, which is a widely distributed neotropical legume species (Papilionoideae, Dalbergieae) and a relevant component of the forb legume guild from the Rio Branco savannas, northern Brazil. The unusual combination of phanerocotylar and foliaceous cotyledons with a noticeably short hypocotyl allows to assign the seedlings of Z. latifolia to the phanerocotylar hypogeal foliaceous (PHF) functional type, which is the first reference to the genus. Resprouting capacity from a bud bank is a common characteristic of taxa with PHF seedlings in savannas and depends on the formation and protection of bud bank organs. In Z. latifolia, root crowns are generated early from the seedling stage as a result of the ontogenetic development of axillary buds and their accessory buds at the cotyledonary node. We examined the ecological role of PHF seedlings in savannas, where this functional seedling type appears to combine the benefits of the photosynthetic efficiency of foliaceous cotyledons with the higher protection offered by hypogeal germination.