Kaolin Particle Film and Water Deficit Influence Malbec Leaf and Berry Temperature, Pigments, and Photosynthesis

Abstract

The effects of kaolin particle film on traits of commercial interest in the red-skinned winegrape cultivar Malbec (Vitis vinifera L.) were evaluated over three growing seasons by measuring the surface temperatures of leaves and clusters, leaf-level assimilation, leaf and berry pigment composition, and yield of vines grown under differing severities of water deficit with and without a foliar coating of particle film. The vines were irrigated with a standard or reduced amount of water and grown under arid field conditions with high solar radiation. Particle film increased the concentration of total monomeric anthocyanins in berries each year and the ratio of anthocyanins to soluble solids at harvest in two out of three years. The particle film did not alleviate differences in anthocyanin concentration between east- and west-exposed clusters. In vines under reduced irrigation, particle film decreased the cumulative minutes that surface temperatures exceeded 30°C between mid-July through harvest in east- but not west-exposed berries and in east-exposed leaves. Leaves with particle film had lower midmorning rates of assimilation, lower chlorophyll-a to chlorophyll-b ratio, and a higher ratio of chlorophylls to carotenoids than leaves without particle film. Decreased assimilation was unrelated to the magnitude of leaf reflectance of visible light. Particle film did not affect yield components or fruit maturity, indicating that net primary productivity was sufficient to ripen fruit to maturity. These results demonstrate that foliar particle film can facilitate the accumulation of anthocyanins in deficit-irrigated Malbec under warm, arid conditions with high solar radiation.