Cold mountain trees may stop growing due to hormones, not hunger
Dietrich L, Zeidler M
Plant Signaling
Next time you hike above the treeline and see stunted, wind-bent trees, you're looking at a plant hormone system putting the brakes on growth, not a tree that's simply run out of food.
Scientists have long assumed that trees stop growing at high elevations or near the Arctic because it's too cold for them to make or use enough sugar for energy. But this idea proposes something different: the trees actually have enough stored energy, they're just being held back by internal chemical signals. Cold temperatures seem to boost a hormone-related brake system called DELLA, which tells the tree's growing tips to stay dormant even though the tree is metabolically fine.
Key Findings
Treelines represent a limit on upright growth form, not a survival limit, since photosynthesis and carbohydrate reserves often remain adequate at these boundaries
Growth cessation is concentrated in apical and cambial (shoot tip and trunk-thickening) tissues, arguing against simple carbon starvation as the cause
Chronic cold may sustain DELLA-like growth-repressor proteins via reduced gibberellin hormone availability, compounded by shifts in auxin and brassinosteroid signaling
chevron_right Technical Summary
Trees at the world's cold-climate treelines aren't running out of fuel; they're being chemically told to stop growing tall. A new hypothesis points to plant hormones, especially a growth-suppressing signal called DELLA, as the reason mountain and arctic trees stall out even when they still have plenty of stored sugar.
Abstract Preview
Original paper
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 sufficien...
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