Influence of light interception on vegetative and productive development of peaches cv. Elegant Lady

This study was carried out in the Upper Valley of Rio Negro (38 degrees 55' South) on peaches cv. Elegant Lady trained as an open vase of 5 m heights and planted at 4 x 4.8 m. Three treatments were applied in a complete randomized design simulating different light intensities: light restriction with shade nets of 80%, summer pruning and control trees. Plants were divided in 4 sectors (East, West, South and North) and 3 different canopy heights. Photosynthetically Active Radiation (PAR) was measured in each sector at 25, 15 and 6 days before harvest. Fifteen days before harvest shoot length, leaf area and shoot specific Leaf weight (SSLW) was determined. At harvest time, fruit color surface (%), color intensity (HUE), weight, diameter, length and flesh firmness was also measured. The intercepted PAR was influenced by the light treatments and height. The vegetative and reproductive variables showed a linear relationship among them and they depended of the PAR intercepted. Models that explain the behavior among PAR and fruit quality variables are asymptotic. To have fruits with the weight and color required for the market the PAR intercepted should be 30% since 25 days before harvest. These variables were very responsive to PAR variations between 0 to 15% of the PAR intercepted. In this range, little PAR variations produced big changes in fruit weight, color surface and hue.