Contribution of intrusive and symplastic growths in wood fibre tip development

Key message

At initial stages of fibre development, radial enlargement of growing fibre tip is achieved, on average, in 37.8% intrusively and in 62.2% symplastically, whereas tip tangential enlargement is purely intrusive.

Abstract

In this study, we have investigated the mode of growth of black locust wood fibre tips at initial stages of their development using detailed measurements. Growth of fibre tips may be considered in three directions: axial, tangential, and radial. An axial elongation of a fibre tip was described as intrusive and related to the separation of walls of neighbouring cells. However, determination of the contribution of intrusive vs. symplastic component of growth in tangential and radial directions was missing. Semi-thin transverse sections of the vascular cambium and adjacent tissues were obtained by ultramicrotome and stained with PAS and toluidine blue. An anatomical analysis of contribution of intrusive and symplastic growths in fibre tip radial and tangential enlargement was performed. Our study showed that during its development an average wood fibre tip grows only intrusively in tangential direction and shows intrusive-symplastic growth in radial direction. On average, at initial stages of its development, a fibre tip radial enlargement is achieved in 37.8% by intrusive growth and in 62.2% by coordinated (symplastic) growth.