A potential role for DELLA signaling in global treeline formation

Treelines mark a functional limit of upright tree growth rather than a strict survival boundary. At these cold margins, photosynthesis and nonstructural carbohydrate reserves often remain sufficient, whereas apical and cambial growth decline, arguing against carbon limitation as the primary cause of growth cessation. We propose that chronic low temperature may contribute importantly to this pattern through hormonal regulation, notably reduced gibberellin availability and persistence of DELLA-like repressors, together with altered auxin and brassinosteroid signaling. This could maintain meristems in a growth-repressive state despite continued metabolic activity. We do not present this as the sole explanation for treeline formation, but as a plausible and testable regulatory mechanism that may operate alongside generally reduced metabolic rates and hydraulic or energetic constraints.