Determination of the Characteristic Structures of Low Temperature Exotherm in Grapevine Buds and Their Relationship with the Bud Structure

This study was carried out to determine the characteristic structure of the low temperature exotherm (LTE) which were determined by DTA (Differential Thermal Analysis) method in the grapevine buds and their relationship with the structure of the bud in the dormant periods of 2016-2018. For this purpose, 8 sample groups, which are structurally different in terms of the numbers of buds and clusters, were designed. In each of the genotypes of the species Vitis vinifera L. ('Karaerik') and Vitis labrusca ('53 Pazar 01'), full bottom bud, full middle bud, full end bud, primary and secondary bud together, primary and tertiary bud together, only the primary bud, only the secondary bud were subjected to DTA test and histological examined. It was found that the sample groups had significant histological differences in terms of the numbers of buds and the clusters. It was determined that the samples with different histological structure produced different character and number of LTE as a result of DTA test. In the study, it was determined that buds were the most important sources of the multiple low temperature exotherms seen in the grapevine dormant buds, furthermore, the clusters could also cause exotherms. In addition, it was determined that the primary buds produced higher energy and longer term low temperature exotherms than secondary and tertiary buds. It is said that the sources of multiple exotherms occurring in the full buds can be determined with the help of the energy and durations of exotherms.