Effects of High Root-Zone Temperature on the Physiology and Growth of Pear (Pyrus communis L., cv. Bartlett) and Quince (Cydonia oblonga Mill., cv. BA29) Plants

Global warming, with rising average temperatures and increasingly frequent extreme heat events, poses a major threat to fruit production systems and food security. Understanding how fruit trees respond to soil thermal stress is therefore critical for developing climate-resilient orchards. In this study, we investigated the physiological and growth responses of potted pear (Pyrus communis) and quince (Cydonia oblonga) plants to root-zone heating. Plants were exposed to different substrate heating regimes, and gas exchange, water status, chlorophyll content, shoot growth, and biomass allocation were assessed. Short-term extreme heating (50 °C for 36 h) caused immediate reductions in gas exchange, severe root and shoot damage, and rapid plant mortality in both species. By contrast, prolonged heating at 40/35 °C induced significant declines in gas exchange, shoot growth, and root biomass, with species-specific differences. Pear exhibited greater sensitivity than quince, showing lower shoot growth, root dry weight, and gas exchange. These findings highlight the vulnerability of pear trees to high root-zone temperatures and the limited contrast between the tested rootstocks. Accordingly, there is a clear need for targeted soil management practices that promote root growth and soil exploration to enhance orchard resilience under future climate scenarios.