Comment: Hypocotyl hairs: an historical perspective

Abstract

The presence of distinctive hypocotyl hairs on young seedlings of some species has been known for some time, although largely ignored. A recent paper (Robinson et al. 2008) suggests that they may be of great ecological significance in the Australian shrub Melaleuca ericifolia. There is a scattered and little-known literature on this topic going back at least as far as 1904. Here, I provide an overview of that literature. The 21 families and 55 genera of flowering plants in which hypocotyl hairs have been recorded are tabulated. The life forms involved range from annual herbs to shrubs and trees and the habitats from marine to freshwater wetlands to fully terrestrial habitats, including those in semiarid areas. The functions attributed to hypocotyl hairs include anchoring seedlings to the substrate, facilitating the development of geotropism and water uptake until the root hairs develop.