The influence of ionic form of silicon on the formation of elementary fibre cells in Cannabis sativa L.

Abstract

 Purpose. To establish the peculiarities of the fibrous layer structure and the degree of variability of the traits of the primary and secondary bast fibre cells in industrial hemp (Cannabis sativa L.) varieties under the influence of exogenous silicon and the possibilities of using it to improve fibre quality.  Methods.  Plants of the ‘Afina’ and ‘Hlukhivski 51’ varieties, grown in an area of 30 × 5 cm, were studied. During the vegetation period, the plants were treated twice or three times with an aqueous solution of K₂SiO₃·5H₂O at concentrations of 2.5 g/L and 5.0 g/L, respectively, at the BBCH development phases 15, 51 and 65. The control variants used distilled water instead of the silicon solution. For the anatomical analysis, transverse sections of bark and wood were taken from the stems at the level of the IV internode (with a diameter of 9.5 mm) and examined using light microscopy.   Results.   In hemp plants under the influence of silicon, the thickness of the bast fibre layer increased, as can be seen from the analysis of transverse stem sections. For the ‘Afina’ variety, the secondary fiber layer thickness increased from 105 μm in the control group to 138 μm in the treated group. For the ‘Hlukhivski 51’ variety, it increased from 163 μm to 230 μm with triple treatment using a 0.5 g/L K₂SiO₃·5H₂O solution. This increase in fiber layer thickness was mainly due to secondary fibers, i.e., silicon activates cambium activity, the secondary generative tissue. The lengths and widths of the primary fibre cells were 40.2 and 25.9 μm for the ‘Afina’ variety and 57.0 and 40.2 μm for the ‘Hlukhivski 51’ variety. The lengths and widths of the secondary fibre cells were 25.1 and 15.5 μm and 33.4 and 16.5 μm, respectively. The increase in cell sizes was due to a decrease in the channel size and an increase in the thickness of the secondary walls. These changed from 6.5 to 12.5 μm and from 16.5 to 19.7 μm in primary bast fibre cells and from 5.5 to 7.2 μm and from 6.0 to 7.6 μm in secondary bast fibre cells in the ‘Afina’ and ‘Hlukhivski 51’ varieties, respectively. An increase in the proportion of isodiametric and oval-shaped cells with a convex contour, as well as cells with a small channel, was observed, indicating a structural rearrangement of fibrous formations. Conclusions. To increase the total fibre content of hemp stems, it is advisable to treat the plants with a silicon (Si) solution during the period of intensive secondary fibre accumulation, and to obtain higher-quality fibre, during the period of intensive primary fibre accumulation.