The structural and chemical characteristics of the pericarp are important in Tilia miqueliana seed dormancy

Abstract

Pericarp structure and permeability in Tilia miqueliana were explored using anatomy, paraffin section detection, scanning electron microscopy, and magnetic resonance imaging. The pericarp of intact T. miqueliana seeds comprised an exocarp, mesocarp, and endocarp. The exocarp was densely covered with villi and consisted of irregular thin-walled cells. The mesocarp was highly lignified and impermeable, with slender, thick-walled, round and irregularly polygonal cells. The endocarp consisted of spherical parenchyma cells. The water gap provided an entry point for free water in intact seeds. The impermeable and highly lignified mesocarp creates a mechanical and permeability barrier, inhibiting germination in T. miqueliana. Liquid chromatography–mass spectrometry was used to identify the chemical composition of the pericarp. Identified compounds included phenols, esters, organic acid, lipids, aldehydes, as well as unsaturated fatty acids, which likely play a role in suppressing germination.