Abstract
Perennial plants in temperate climates evolved short and long-term strategies to store and manage reserves in the form of non-structural carbohydrates (NSC; soluble sugars (SC) and starch (St)). NSC storage allows plants to survive seasonal periods of photosynthetic inactivity (dormancy). To study year-to-year seasonal patterns of trees’ NSC dynamics that control phenology and yields, we established a large scale, multi-year study called the “Carbohydrate Observatory” using a citizen science approach with ~ 590 sites throughout the Central Valley of California. Monthly sampling tracked seasonal trends of starch and sugar levels in both xylem and phloem of twigs in Prunus dulcis, Pistacia vera and Juglans regia. Presented is the initial technical analysis of the first 3 years. With no exception, levels of reserves changed continuously throughout the year suggesting that even during dormancy, the average concentration of NSC, starch and sugars varies seasonally. In general, carbohydrate reserves are highest entering dormancy. During winter, NSCs slowly decrease to depletion during bloom time and remain low during summer until recovery near harvest. Starch is the major reserve compound in the wood of P. dulcis and P. vera while soluble sugars are the major reserves in J. regia. NSC content fluctuates throughout a season and significantly varies between years suggesting intrinsic and climatic effects on trees’ energy reserves.
Highlights
Perennial plants in temperate climates evolved short and long-term strategies to store and manage reserves in the form of non-structural carbohydrates (NSC; soluble sugars (SC) and starch (St))
We focused our analysis on NSC content in twigs
Compared to other parts of the tree, twig NSC content follows a general pattern of NSC seasonal variation[14,27] and correlates with or even affects major phenological events[28] whereas roots remain fairly stable throughout the year despite the stem wood having the biggest biomass, branches are the largest reservoir of total NSC followed by roots and stem w ood[14]
Summary
Perennial plants in temperate climates evolved short and long-term strategies to store and manage reserves in the form of non-structural carbohydrates (NSC; soluble sugars (SC) and starch (St)). NSC exist as two pools: chemically active soluble carbohydrates (SC) present as mono and disaccharide sugars like glucose, fructose, and sucrose and sometimes sugar alcohols like sorbitol, and inactive, insoluble starch (St)[1,2,3] These two pools of carbohydrates are under biological control that evolved to meet demands of species-specific internal (physiology) and external (environmental) properties[4]. The amount of NSC reserves ahead of the winter should be enough to sustain winter respiration and spring demands for bloom and leafing Species vary in their seasonal pattern of NSC reserve pools based upon vegetative habit, reproduction, growth, and duration of d ormancy[4,14]. As orchard trees were presumably selected for high productivity in expense of energy reserves security, even small changes to NSC management induced by climate change or management practices can disproportionally affect productivity and orchard health
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