CHITOSAN CANOLA SEED COATING: ROOT SYSTEM AND DEFENCE RESPONSES

Abstract

Chitosan is a natural polymer with biostimulant properties known to enhance plant defence responses. However, when applied as a seed coating technology, its effects on root growth are not fully understood. This study aimed to (i) develop a reproducible protocol for callose detection in canola roots as a functional marker of immune activation induced by chitosan under direct exposure; and (ii) evaluate the physiological, morphological, and growth effects of different chitosan seed coating formulations, with particular emphasis on distinguishing immune-mediated responses from the physicochemical properties of the coating matrix. In Stage 1, canola roots were immersed in 0.01% and 1% chitosan solutions to induce callose deposition as an immune response. In Stage 2, different seed coating formulations with chitosan (liquid and solid), sodium alginate, and talc were evaluated in terms of callose deposition, radicle and seedling emergence, seed water uptake, root length and electrolyte leakage. Callose deposition was observed under direct exposure, but not after seed coating treatment. Early physiological responses were instead primarily associated with the physicochemical properties of the coatings and their effects on water uptake. Liquid chitosan delayed radicle emergence by limiting hydration, whereas alginate and talc accelerated it. Seedling emergence, root length, and membrane integrity remained unaffected. The initial delay in radicle emergence caused by liquid chitosan did not compromise seedling growth. A reproducible protocol for callose detection as a marker of immune response was successfully developed. Under the tested conditions, these results highlight the critical role of the application method in determining chitosan bioactivity.