LAUSR

Global warming will disturb dormancy release and growth resumption of trees. To better understand this process, it is important to investigate physiological and biochemical traits related to these stages. We examined dormancy release and growth resumption in Japanese cedar (Cryptomeria japonica [L.] D. Don), an evergreen needle-leaved tree, in the warm-temperate zone by evaluating budbreak under growth-promoting conditions, and simultaneously examining respiration rates and contents of carbohydrates and phytohormones in shoots from November 2022 to March 2023. A long time to budbreak and the lowest budbreak rates of 75% in November indicated shallow dormancy. Budbreak rates of 98%, short time to budbreak, and first appearance of budbreak in the field in March indicated growth resumption. Continuous changes in budbreak rates and time to budbreak between dormancy and growth resumption indicated dormancy was gradually released. Surges in budbreak rates in December indicated dormancy was almost completely released by early winter. Contents of abscisic acid (ABA) and salicylic acid (SA) decreased from November, remained low in March, and were strongly associated with budbreak rates according to principal component analysis. It was suggested that the depletion of SA led to the depletion of ABA, contributing to dormancy release and growth resumption. Fructose and trans-zeatin accumulated until February, and low levels of starch, indole-3-acetic acid, jasmonic acid, and jasmonic acid-isoleucine during winter was followed by accumulation in March. Although these biochemical traits were less related to budbreak rates compared to ABA and SA, they seemed to assist either dormancy release or growth resumption. In response to the threat of global warming to forests, there is a pressing need to understand the mechanism of dormancy release in trees. In this study, we observed physiological and biochemical traits related to dormancy release in the Japanese cedar (Cryptomeria japonica [L.] D. Don). We found that abscisic acid and salicylic acid were specifically related to the process of dormancy release, while other phytohormones, carbohydrates, and respiration were less related to dormancy release. Moreover, the possible interrelationships between physiological and biochemical traits hypothesized in this study will help future research to unravel the mechanism of dormancy release.