UC Davis

This research venture presents three distinctive studies, employing non-structural carbohydrate (NSC) measurements as an effective tool to evaluate plant responses under varied environmental conditions.

Chapter One focuses on how the rate of drought development impacts energy reserves and the recovery process in Grenache, a cultivar. The research studied fast-developing drought (FDD) and slow-developing drought (SDD). FDD, characterized by rapid stomatal closure and high abscisic acid (ABA) accumulation, showed negligible stem priming for recovery. However, SDD exhibited gradual stomatal closure, lower ABA accumulation, and changes preparing the stem for recovery, including xylem sap acidification and sugar accumulation. Both drought types showed similar trends concerning stomatal conductance recovery, yet displayed different sensitivities to xylem ABA. Total NSC content in plant stems was affected differently by FDD and SDD. FDD didn't significantly alter total carbohydrate content, whereas SDD led to an increase during stress, which normalized post-recovery. FDD resulted in a higher stem starch content during drought and post-rehydration, with no significant change in soluble sugar accumulation. SDD plants accumulated slightly more starch and significantly more soluble sugars, which returned to pre-stress levels swiftly after rehydration. This study indicates plants' unique adaptability to long-term drought and highlights the need for accurately reflecting field conditions when studying plant responses to drought.

Chapter Two investigates the impact of extended smoke exposure on NSC reserves in trees under natural field conditions. The study analyzed a comprehensive regional dataset and detailed spatiotemporal satellite data. Results showed that mid-growth season smoke exposure could transiently deplete plants' NSC reserves, while exposure later in the growth cycle could disrupt the vital carbohydrate reserve buildup, leading to a prolonged reduction in reserves. This introduces an unrecognized risk to plant health and ecosystem stability, threatening both agricultural and natural environments on a regional scale.

Chapter Three explores climate change implications on almond orchard phenology and the subsequent land suitability for almond farming. This study utilized historical climate data, a model incorporating daily minimum/maximum temperatures and NSC dynamics in twigs, and CMIP6 climate predictions. Analysis under two climate change scenarios projected that land suitable for almond farming could remain largely stable over the next three decades. However, under the unchanged emission scenario, the suitable land could see a reduction ranging from 50% to 95% by the century's end, aligning with a shift in bloom time. This signifies the critical role of climate change in shaping almond production's future, emphasizing the need for sustainable agricultural land management, ensuring long-term food security and economic stability amidst evolving climate conditions.

In conclusion, the research presents valuable insights into plants' adaptability and resilience under different environmental stressors. It demonstrates the importance of NSC measurements in understanding these responses, opening avenues for future research and effective adaptation strategies in the face of changing environmental conditions. It also underscores the pressing need to address the risks and challenges posed by climate change and other anthropogenic factors to ensure sustainable agricultural practices and ecosystem stability.