Cytoskeletal Regulation of Wood Formation and Stress Adaptation in Woody Plants.

The cytoskeleton regulates cell division, intracellular transport and cell-wall patterning, but its roles in secondary growth and long-term stress responses in woody plants remain poorly understood. We classify individual claims as direct functional evidence from woody species (Level I), correlative or functionally non-specific evidence from woody systems (Level II), mechanisms demonstrated only in non-woody models (Level III), or relationships untested in woody plants (Hypothesis). Direct functional evidence remains concentrated in Populus. In hybrid poplar, PagPCaP1a promotes salt-induced microtubule depolymerisation, while its genetic inhibition improves salt tolerance. Separate studies report that tubulin perturbation alters developing xylem pectin and xylan extractability and leaf stomatal kinetics. Woody studies associate microtubule-related factors with cambial cytokinesis, reaction wood, microfibril angle and xylem anatomy, but do not establish causality. Microtubule-cellulose synthase coupling and actin-dependent trafficking are supported mainly by non-woody models, whereas proposed cytoskeletal roles in secondary-wall delivery, xylem programmed cell death, wood mechanics, hydraulic safety, stress memory and immunity remain untested. Resolving these gaps requires cell-type-specific perturbation and live imaging in cambium and developing xylem, combined with wall, anatomical, mechanical and hydraulic measurements across woody lineages and validation in whole trees.