Chilling-Requirement Release of Seed and Bud Dormancy in Apricot

Abstract

Dormancy shows common physiological features in buds and seeds. Specific period of chilling is usually required to release dormancy. Reproductive meristems and embryos display dormancy mechanisms in specialized structures named respectively buds and seeds that arrest the growth of perennial plants until environmental conditions are optimal for survival. Chilling requirements for breaking dormancy were studied for 3 successive years in 20 seedling apricot trees which spanned the range of flowering times in these trees. Different methods for estimating chilling requirements were evaluated and compared, and correlations between chilling requirements and flowering date were established. The trees examined showed a range of chilling requirements, chill hours (CH) between 199 CH and 274 CH, and chill units, (CU), between 612CU and 873CU. The results obtained in different years by the Utah and Dynamic models were more homogeneous with respect to the hours below 7 °C model. The apricot trees showed important differences concerning flowering date, and the results indicate a high positive correlation between chilling requirements and flowering date.Moreover, a specific low-temperature stratification treatment was required to overcome seed dormancy. 5°C cold stratification was found to be the best for breaking seed dormancy and germination. Increased seed germination percentage was recorded when the period of stratification prolonged. Apricot seeds required a cold stratification of about 12-15 days to reach maximum germination.

Effects of Low-Temperature Accumulation on Flowering of Prunus mume

“…[12]. El-Yazal (2020) conducted a study on the low-temperature conditions of breaking dormancy for 20 apricot seedlings for three consecutive years and found that cold stratification at 5 • C had the best effect on breaking seed dormancy and germination [19]. Heide and Prestrud (2005) studied the growth and dormancy of four apple cultivars and one pear cultivar and found that at least 6 weeks (about 1000 h) of chilling at 6 or 9 • C were required for the release of dormancy and recovery of growth, while chilling at 12 • C for 14 weeks treatment is almost ineffective [10].…”