Growth-Rings in Apple Trees Function as Source and Sink to Balance Impact of Drought Stress

Annual growth-ring increments integrate every growth factor including climatic changes and they can be measured and evaluated retrospectively. Therefore, this parameter was used in apple trees grubbed in autumn 2005 to trace back information on growth response of five apple cultivars grafted on M9 rootstock, including one red mutant ('Boskoop', 'Cox Orange', 'Elstar', 'Red Elstar', 'Golden Delicious', and 'Jonagold') during 17 to 19 years of cultivation under two different production systems with special focus on the drought conditions of the year 2003. From the results it is to be concluded that the production system was of major importance for annual radial growth in the apple cultivars studied. Best use can be made of the tolerance against drought inherent to apple trees by integrated fruit production, which proved to be superior to alternate fruit-bearing in the aspects under study.