Dynamic Source-Sink Regulation and Carbon Allocation in Fruit Crops: Implications for Yield, Quality, and Climate Resilience

Abstract

Carbon allocation and source-sink interactions are fundamental determinants of yield, fruit quality, and climate resilience in perennial fruit crops. Unlike annual species, fruit crops must continuously distribute assimilates among reproductive, vegetative, and storage sinks, balancing current production with future growth. Although photosynthetic carbon supply has traditionally been regarded as the primary driver of productivity, increasing evidence shows that sink demand actively regulates source activity through metabolic and signalling feedback, making crop performance dependent on the coordinated interaction of source capacity, sink strength, phloem transport, and non-structural carbohydrate reserves. This review synthesizes current physiological, biochemical, and modelling knowledge to develop an integrated framework for understanding carbon allocation in major fruit crops, including apple, grapevine, citrus, peach, and mango. It examines the roles of carbohydrate reserves, sink activity, and phloem transport in regulating fruit growth, quality, and seasonal carry-over effects, while highlighting the impacts of drought, heat stress, elevated atmospheric CO₂, and nutrient limitations on source-sink coordination. Emerging approaches for analysing carbon dynamics and key research priorities are also discussed. Optimizing sink activity and reserve dynamics, together with climate-smart orchard management, is essential for sustaining fruit productivity, quality, and resilience under changing climatic conditions.