Warm winter temperature induced changes in the dormant buds of ‘Dangshansuli’ pear (Pyrus bretschneideri Rehd.)

Winter dormancy is one of the crucial ways leading to the survival of deciduous fruit trees in the temperate and boreal zones. In order to study the effects of higher winter temperatures, such as caused by global warming, on bud dormancy and related hormone abundance in ‘pear, a greenhouse was set up to enclose adult trees of the pear in field, the temperature inside the greenhouse was maintained about 3.0°C higher than that in the open field. Our results indicated that, greenhouse grown pear trees resulted in about 7-day delay of dormancy induction, 4–5 days ahead of dormancy breaking and much quickly into deep dormancy compared to control trees. Higher temperature led to significant changes of indole-3-acetic acid (IAA), gibberellin acid (GA3), zeatinriboside (ZR), and abscisic acid (ABA) contents as well as lower ratios of ZR/GA3, ZR/IAA, ABA/GA3, and ABA/IAA in flower buds but not vegetative buds, suggesting that higher winter temperature did not favour flower bud dormancy breaking. Over the dormancy period, ABA content, but not IAA, GA3 and ZR, in flower bud increased alone with the decreased temperature and peaked at the deep dormancy stage, suggesting a great role of ABA in flower bud dormancy formation. The data suggested that higher winter temperature has negative effects on pear flower bud dormancy.