IMPACTS OF LEAF AREA ON THE PHYSIOLOGICAL ACTIVITY AND BERRY MATURATION OF MERLOT (VITIS VINIFERA L.)

The aim of this research was to understand some physiological and agronomical behaviors of the Merlot grapevine subjected to different canopy management practices under the climatic conditions of different growing seasons in Tekirdag, Turkey. The resulting must composition and berry maturation were also determined. Adult vines of Vitis vinifera L. cv. Merlot, grafted onto 5BB were applied to different leaf areas (various levels of leaf removal from main and lateral shoots) during the growing season. Leaf photosynthesis (A) and transpiration (E), stomatal conductance (g(s)), yield parameters, maturation indices and berry composition at harvest were analyzed over a period of three consecutive years between 2013 and 2015. In the vegetation periods of 2013 and 2015 when there is less precipitation, proportional humidity is relatively low and temperatures are high, positive results were obtained in terms of quality criteria in half lateral shoots (3-4 leaves= HLS) application. Under extreme rainfall and high relative humidity conditions as in 2014, none lateral shoots (NLS) application increased physiological activity and relative quality. The main factor controlling the physiological behavior and grape ripening in Merlot vines was largely dependent on the meso-climatic conditions during the growing season. However, the total effect of small differences in the canopy microclimates created by different leaf area reduction applications affected the indicators of industrial maturity at the end of vegetation. Planning of canopy management practices should be done by taking into consideration long- and medium-term meteorological evaluations, and short-term planning within vegetation should be considered by weighing weekly and monthly meteorological risks.