In-field assessment of grapevine water status using a portable NIR spectrophotometer

GrapevineRSQUOs growth, yield and berry composition are impacted by water status. Most of the methods employed to assess grapevine water status are time consuming and provide information of limited number of vines, hence jeopardizing their representativeness. NIR measurements were taken in 20 leaves (adaxial and abaxial sides) of the mid-upper part of the canopy per each of the following red (Vitis vinifera) cultivars: 'Cabernet Sauvignon', 'Tempranillo', 'Marselan' and 'Grenache'. Concurrently, the stem water potential (Ψs) and the relative water content (RWC) were determined on the same leaves. RWC ranged from 46.9 to 98.2% and Ψs ranged from -0.80 to -1.85 MPa. Predictive models based on partial least squares using the reflectance spectra and the first and second derivative were built. The most informative band was centered at 1927 nm and consistently higher absorption values were observed for the adaxial side. The prediction capability of this non-invasive spectral technique was substantially higher for stem water potential in adaxial (r=0.91) and abaxial side (r=0.93) than for the leafRSQUOs relative water content (r=0.66 and r=0.73).