Plant Growth Regulators, Biostimulants and Growth‐Promoting Microorganisms in Miscanthus : A Scoping Review of Evidence, Experimental Designs and Research Gaps (2010–2025)

ABSTRACT Miscanthus is a leading lignocellulosic crop for low‐carbon bioenergy systems, yet its deployment is limited by establishment challenges, early‐stage growth variability and performance constraints on marginal or contaminated soils. Plant growth regulators (PGRs), biostimulants (BS), and growth‐promoting microorganisms (GPMs) have been proposed to enhance establishment and stress tolerance, but evidence remains fragmented across species, environments, and application strategies. This scoping review systematically mapped peer‐reviewed experimental studies published between 2010 and 2025, following PRISMA‐ScR guidelines. Searches across Scopus, Web of Science and PubMed identified 252 records, of which 29 met the inclusion criteria after screening and deduplication. Data extraction captured species, planting material, growth environment, soil context, intervention class, application strategy, outcome domains and effect direction. The evidence base was dominated by Miscanthus × giganteus (52% of studies), rhizome‐based planting material, controlled environments and short‐duration experiments. GPMs and BS were the most frequently tested interventions, occurring in approximately 93% of studies. Growth outcomes were assessed in 26 of the 29 studies and were predominantly positive. Across studies reporting comparable data, the best‐performing treatments produced increases in above‐ground biomass ranging from approximately 15% to 200% relative to controls, while shoot‐height responses ranged from negligible effects to increases exceeding 100%. Photosynthesis‐related parameters, including photosynthetic rate and chlorophyll, also showed variable but generally positive responses. However, physiological and remediation outcomes were less consistently assessed and exhibited greater heterogeneity. The review highlights substantial methodological clustering and identifies critical gaps in long‐term field studies, seed‐ and plug‐based systems, and integrated physiological–remediation assessments needed to support scalable, net‐zero‐aligned Miscanthus deployment.