(In)determinacy in Woody Plants: Limits and Opportunities for Timing Growth in a Changing Climate.

When and how much plants grow under environmental constraints are fundamental questions in biology and increasingly important for predicting biomass production and carbon sequestration under climate change. While temperature and water availability directly regulate plant growth, the timing and rate of growth are also shaped by internal developmental programming, though this is rarely considered in predictions of tree growth responses to future climates. Here, we revisit a concept central to this internal programming-(in)determinacy. Focusing on woody plants, we define it as the extent to which annual shoot growth is deployed from preformed organs versus produced de novo during the current season. We argue that this trait is best understood as a continuum and that it can help explain contrasting growth responses in a changing climate. More determinate species concentrate growth within a narrow seasonal window, which may reduce exposure to late-season stress but also limit their ability to exploit longer growing seasons. More indeterminate species retain greater flexibility to extend or resume growth when conditions remain favourable, which may be advantageous under climate change, but this same flexibility may also increase exposure to frost, drought and incomplete tissue maturation. Because primary shoot growth also shapes canopy development and is linked to other growth processes, variation in (in)determinacy could help explain broader differences in whole-plant performance, carbon gain and species responses to climate change.