Abstract
Fruit growth is driven by the interaction of environmental cues and phytohormonal signals. Biophysical models have captured the general trend of fruit growth but often overlook the regulatory role of phytohormones. This study integrates a biophysical framework with the quantitative response of endogenous abscisic acid (ABA) in fruit. ABA dynamics are incorporated as a ripening signal, influencing sugar uptake, respiration, hydraulic conductance and transpiration processes. The model has been primarily tested on blueberries, a fruit with well-characterised ABA responses. Simulations show predictive accuracy and explanatory capability for fruit mass under variable climatic conditions. Notably, the model effectively simulates the impacts of environmental stresses such as heat, cold and drought, capturing the resulting physiological delays in fruit growth. Our research underscores the potential of integrating phytohormonal responses into biophysical models, providing key insights into fruit growth dynamics and practical guidance for optimising crop management under increasing climate uncertainties.