Spring frosts in deciduous fruit trees Ð morphological damage and ̄ower hardiness

Freeze injury is one of the main limiting factors to crop production and distribution of horticultural crops. Despite the numerous research efforts devoted to reduce freezing injury, it still accounts for greater losses of fruits and vegetables than any other environmental or biological hazard and the ultimate causes determining cold hardiness remain uncertain. In temperate climates, important damages on deciduous fruit trees are produced in buds, ̄owers and developing fruits after dormancy and losses due to frosts during bloom are usually more important than those due to low winter temperatures. The information available on the in ̄uence of late spring frosts on reproductive organs of deciduous fruit trees in temperate climates is reviewed. The freezing process is examined, paying attention to how subsequent frost damage is caused at the cellular level as well as its anatomical and morphological consequences in ̄owers and fruits. The ̄ower hardiness response is evaluated in terms of genotype, phenology and a number of physiological aspects as the formation of ice nucleation, moisture content and nutritive status. Finally, new perspectives are explored. # 2000 Elsevier Science B.V. All rights reserved.