Cold Hardiness, Sorbitol, and Sugar Levels of Apple Shoots as Influenced by Controlled Temperature and Season1

Storage temperature and season markedly affected cold acclimation and deacclimation and levels of sorbitol and sugars in 1-and 2-year excised apple (Malus domestica Borkh) shoots. Cold hardiness of shoots increased with a decrease in storage temperature (2 to −18°C) from August to January, then decreased as growth began in March. In most seasons, cold hardiness was significantly related to high levels of sorbitol in the sap, and to high levels of sucrose and total sugars (fructose, glucose, sucrose and sorbitol) in the combined bark and wood samples.