Seasonal patterns of sugar components and their functions in branches of Fagus crenata in association with three reproduction events

Abstract

AbstractSoluble sugars have multiple functions in plants and both their absolute and relative abundances may vary in association with diverse physiological processes and life‐history events. Some also have specific functions in different organs that vary seasonally. Therefore, studying the dynamics of sugar compositions in woody species would further our understanding of their functions, which has been mainly analyzed en bloc. In order to elucidate the functions of specific soluble sugars and the effects of reproduction on their profile, we monitored the soluble sugar composition in “new” (current‐year) and “old” (1–3 years old) branches of Fagus crenata for 7 years, which included three reproduction (“masting”) events. As well as the generally predominant sugar species (sucrose, glucose, and fructose), substantial amounts of raffinose (accounting for up to 42% of the total sugars) were found in both new and old branches during winter hardening. In addition, myo‐inositol (which plays important roles in cell growth and development) was detected mainly during the early growing season and fluctuated interannually in both new and old branches. Furthermore, the only clear change in soluble sugar contents associated with reproduction events was in myo‐inositol concentrations in the new branches, which were lower in fruiting trees than in non‐fruiting trees, possibly due to the growth reduction in fruiting tree branches identified in previous studies. The results show the importance of considering the dynamics of each sugar component, rather than en bloc, in attempts to elucidate their roles in physiological processes and responses to environmental changes.