Growth and currency of wine, differences of five grape varities in adaption to climate change, Rheingau, Germany

For photosynthetic capacity we used a Licor 6400 to derive A-Ci curves (curves of the response of photosynthetic rate to changes in leaf internal CO2 concentration) following the field protocol used by Xu and Baldocchi (2003). This protocol involves allowing the leaf to acclimatise for 30 minutes to a high (1000 ppm) chamber CO2 concentration and then programing a decrease in CO2 concentration in the sequence 1000, 700, 500, 360, 200, 150, 100, 50 ppm. The leaves were given eight minutes to acclimatise to each CO2 level before measuring the gas exchange parameters. Light intensity was set to 800 mymolm2s-1.