Relationships between Water Status, Leaf Chlorophyll Content and Photosynthetic Performance in Tempranillo Vineyards

The aims of this work were (i) to study the relationships between leaf water potential, foliar chlorophyllcontent and photosynthetic performance of grapevines under field conditions, and (ii) to evaluate thefeasibility of chlorophyll fluorescence parameters to assess water status in commercial vineyards. Duringthree consecutive seasons (2011 to 2013), 20 non-irrigated “Tempranillo” vineyard subzones were monitoredin Ribera del Duero, Spain. Data on foliar chlorophyll content, midday and predawn leaf water potential,net assimilation and chlorophyll fluorescence parameters were measured at fruit set, pre-véraison andvéraison. The results show that the water potential indicated weak to moderate stress in the study yearsand decreased along the vegetative cycle, while foliar chlorophyll contents showed an increasing trend. Thecorrelation between both variables was not consistent. Linear regression of the chlorophyll fluorescenceparameters in dark-adapted leaves, Fo, Fv and Fv/Fm, over chlorophyll content was strong in all thestudy years (higher determination coefficients for Fv/Fm at fruit set in 2012 and 2013). In general, thewater potential with low coefficients of variation showed a low effect on photosynthesis activity, althoughvalues in variables such as Fm, Fv, Fv/Fm, Fs/Fo and ΦPSII registered an increasing trend when middayleaf water potential decreased in the pre-véraison and véraison stages. These variables could be useful toestimate water status in commercial vineyards for application in precision viticulture.