Scaling plant responses to heat: From molecules to the biosphere

Predicting plant responses to rising temperatures, including acute heat waves and hot droughts of varying intensity and duration, is central to addressing the climate and biodiversity crises. However, plant responses to heat are scale-dependent, complicating cross-scale prediction. We highlight recent progress revealing how and why plant responses to heat change across scales, including scales of biological organization and space versus time. We give examples of scaling up from molecular- and leaf-scale data and processes, which are modified by homeostatic and buffering mechanisms at whole plant and ecosystem scales. We show that scaling down-predicting plant responses to warming from broad-scale spatial patterns-can also be misleading, even in direction. Addressing such scale dependencies is essential to improving the prediction of plant responses to heat.