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.
Highlights
The majority of trees in temperate climates fulfills a chilling demand (CR) in so as to overcome endodormancy and has a requirement of heat for flowering [1]
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 apricot trees showed important differences concerning flowering date, and the results indicate a high positive correlation between chilling requirements and flowering date.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
Summary
The majority of trees in temperate climates fulfills a chilling demand (CR) in so as to overcome endodormancy and has a requirement of heat for flowering [1]. Chilling Hours (CH) is that the easiest way to estimate chilling requirement. It is measured as the accumulated quantity of hours with temperatures 45°F (7.2°C ) or lower throughout an industry designated time period ( in the study area November 1st to March 30th )[2,3,4,5,6]. CR constrains the acceptable areas of cultivation of the various commercially important tree species and cultivars around the world. Previous studies have indicated that CR might be quantitative character controlled by minimum of one major sequence [16,17,18,19,20]
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