The role of chemical and hydraulic signalling in the recovery of photosynthesis following a rootzone water deficit stress in Rubus idaeus (red raspberry)

With the changing UK climate, abiotic stresses are becoming more prevalent in the UK, causing major effects on crop yield and quality. Abiotic stresses have been researched extensively on crops, including tomato and grapevine, but are limited on the response and recovery of raspberry plants from a water deficit stress. The aim of this PhD research was to improve knowledge of the impact of transient rootzone water deficit stress on red raspberries and to understand signalling mechanisms controlling the response. The effects of different rooting volume pots under water deficit stress conditions were also analysed. Moreover, the investigation studied the impacts of transient rootzone water deficit stress on marketable yield and quality of raspberries. The recovery of leaf gas exchange depended on the duration and intensity of the rootzone water deficit stress. However, even for a deficit of four days, legacy effects on photosynthesis persisted for days after rewetting of the coir. More than a 50-fold increase in xylem-borne ABA was recorded after four days of coir drying, indicating a role of signalling mechanisms in the response to transient rootzone water deficit stress. Effects on Class 1 yield were substantial after a transient rootzone deficit stress reducing yield and impacting berry fresh weight for several weeks. Finally, results highlighted that the use of larger rooting volume pots would likely minimise the adverse effects of water deficit stress. Even short durations of water deficit stress can significantly impact plant physiology, substantially affecting both yield and quality, highlighting the necessity of comprehending not only plant abiotic stress perception but also the recovery response. An integrated approach to understanding combined stress events is imperative for elucidating real-life scenarios. Ultimately, this study contributes to a deeper understanding of raspberry plant responses to water deficit stress, progressing toward preventing legacy effects on leaf gas exchange.