Dark respiration in leaves, stems, and fruits of Corylus avellana

Dark respiration (Rd) is a fundamental process in plant physiology. It reduces the carbohydrates gained via photosynthesis to CO2 and produces energy that can be used to satisfy the maintenance needs of organs and contribute to their growth. Because Rd is involved in the formation of new organs, it is also driven by the size and growth stage of each organ. In this work, we aimed at investigating how changes in temperature and relative growth rate (RGR) impact Rd in leaves, stems and fruits of filbert (Corylus avellana), and to assess if there are critical stages during which respiration peaks can pose a limitation to the fruit set. Rd was measured on leaves, stems and fruits of "Tonda di Giffoni" during the spring and summer of 2021. Rd in filbert leaves, stems and fruits widely varied according to temperature and RGR. The results indicate that when the nut shell grows, the carbon demand, in terms of Rd, was two-fold compared to other organs. High carbon demands have significant consequences on carbon partitioning among organs and the occurrence of possible carbon shortages limiting nut yield. Rd relationships with temperature and RGR are fundamental for the parametrization of future Rd models for filbert, and the optimization of appropriate horticultural techniques to reduce the carbon limitation to fruit set.