Flower bud development and chilling requirements in 'Bing' sweet cherry

7 Pags.- 2 Figs. Original work presented by the authors at VII International Cherry Symposium (Plasencia, Spain. June 23-June 27 2013). The definitive version of the article is available at: http://www.actahort.org/index.htmIn order to survive low temperatures, fruit trees in temperate regions stop their growth and enter dormancy. This is not just a survival strategy; chilling is also a prerequisite for adequate flowering. Chilling requirements are specific for each genotype and determine the possible geographical distribution of the different cultivars. In spite of the relevance of dormancy for fruit production, very little is known on the biological events during this time in flower buds, in which no visible changes can be observed until bud burst. In this work, flower bud development has been sequentially examined in sweet cherry (Prunus avium L. 'Bing') grafted on Santa Lucia 64 rootstock, in relation to dormancy and chilling accumulation. The work was performed over two consecutive years, paying attention to the possible anatomical and cytochemical changes accompanying dormancy. Results showed that, while no anatomical variations occurred along dormancy, conspicuous cytochemical changes could be tracked along this period that may help to understand the requirement for chilling.This work was supported by Ministerio de Economı́a y Competitividad (MINECO) - European Regional Development Fund, European Union (Project grants: AGL2012-40239- C02, INIA RFP2012-00017-C03 and INIA RTA2014-00085-00-00) by Grupo de Investigación de Aragón A-43 (Gobierno de Aragón - European Social Fund). E.F. was supported by the Ministerio de Economı́a y Competitividad by a doctoral fellowship (FPI BES-2010-037992).Peer reviewe