Abstract
In order to produce the physiological bases for choosing early- flowering varieties that may avoid the depleted low winter temperatures, the early and late- opining apple variety Barkhar, Local and Strakhan (Malus sylvestris) were wont to study the relation between the seasonal changes and these balance of endogenous hormones and flower opining date. An improved understanding of the factors governing budburst and development, and their underlying mechanisms is crucial for management of trees performance and yielding. This study investigated variations in chilling requirements, bud burst and development in early and late varieties of apple trees. The budburst and hormonal profile of flower and vegetative buds of early and late varieties were additionally investigated. Results showed less bud burst in late varieties than in early ones. In the former, there were increased in promoters (indole-3-acetic acid and gibberellins) at budburst. Although endogenous inhibitors levels of abscisic acid were considerably reduced by bud development in all varieties. We conclude that late varieties (Strakhan) are less economical in manufacturing new growth, as indicated by less bud vigor at budburst than early varieties (Barkhar and local) and show a marked differential hormonal pattern throughout bud development compared to early varieties.
Highlights
The majority of trees in temperate climates fulfills a chilling demand (CR) to overcome endodormancy and has a requirement of heat for flowering (Campoy et al 2012)
Strakhan varity needed more of chilling hours accumulative at low temperature (7.2°C) than Barkhar and Local for bud break
Our results showed that when the dormancy released, indole-3-acetic acid (IAA)/abscisic acid (ABA) ratio had the same changing tendency to IAA content (Table 8)
Summary
The majority of trees in temperate climates fulfills a chilling demand (CR) to overcome endodormancy and has a requirement of heat for flowering (Campoy et al 2012). If chilling requirements don't appear to be met, irregular, delayed and asynchronous growth, flowering and fruit set can be found in subsequent season if chilling requirements don‘t appear (Luedeling et al, 2009, Campoy et al, 2011). One of the possible effects of temperature change can be a delay inside the beginning of chill accumulation; the fulfillment of chilling requirements and the time at those trees become receptive to heat through spring. Since flower and leaf emergence result from a minimum of part consecutive fulfillments of cold (‘chilling’) and warm (‘forcing’) requirements, later and slower chilling accumulation should end in later flower and growth in spring (Luedeling et al, 2013)
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