Leaf area and leaves gas exchange of ‘Sangiovese’ grapevine produced in high altitude regions of Santa Catarina State, Brazil

The objective of this study was to determine the best mathematical equation to estimate leaf area, quantify the photosynthesis and correlate with yield and grape quality of ‘Sangiovese’ cultivar, during 2011/2012 season, in high altitude region of Santa Catarina State, Brazil. The experiment was conducted in Água Doce-SC, at Villaggio Grando winery (26°43’92”S, 51°30’72”W, altitude 1,350 m) during 2011/2012 season, the plants were trained in vertical shooting positioning trellis and spacing 1.5×3.0 m. To estimate leaf area (LA) the length (cm) of the central vein (CV) of right lateral vein (RLV) and left lateral vein (LLV) was measured in 70 leaves. The leaf area of each leave was measured with a portable analyzer (AM 300 ADC, England). From these measurements it was established the better relation between the leaf area and the length of veins, by mathematical model. Leaf gas exchange was measured with an Infra-Red Gas Analyzer (IRGA LI-6400XTR) during veraison and harvesting in six adult leaves. The CO2 assimilation was measured at photosynthetic photon flux density, of 0, 100, 250, 500, 1,000, 1,500 and 2,000 µmol m-2 s-1. The results showed that the best mathematical model was LA=∑(LLV + RLV), producing the equation y = 0.3213x2 + 0.4883x - 0.6559 (R2=0.97). Maximal photosynthetic rate was reached at 1,000 μmol m-2 s-1. In veraison it was 18.10 µmol CO2 m-2 s-1 and at harvesting 15.99 μmol CO2 m-2 s-1. The results indicate that ‘Sangiovese’ showed balanced vegetative growth and enough photosynthetic activity to supply clusters demands, despite the yields obtained in vineyard was considered low. These results indicate that in this cultivar is possible to increase the yield maintaining the quality of grape improving the ratio between grape production and leaf area