Intrusive growth of primary and secondary phloem fibres in hemp stem determines fibre-bundle formation and structure

Abstract Plant fibres – cells with important mechanical functions and a widely used raw material – are usually identified in microscopic sections only after reaching a significant length or after developing a thickened cell wall. We characterized the early developmental stages of hemp stem phloem fibres, both primary and secondary, when they still had only a primary cell wall. We gave a major emphasis to the role of intrusive elongation, the specific type of plant cell growth, by which fibres