Submitted to: Acta Horticulturae
Publication Type: Proceedings
Publication Acceptance Date: December 7, 2006
Publication Date: June 2, 2008
Citation: Shellie, K., Glenn, D.M. 2008. Wine grape response to kaolin particle film under deficit and well-watered conditions. Acta Horticulturae. 792:587-591. Interpretive Summary: Kaolin is a type of inert clay used in many manufactured products including toothpaste and cosmetic powders. It was developed for use in agriculture to spray on crops for surface protection against sunscald because its white appearance reflects wavelengths of energy that conduct heat and damaging ultraviolet radiation without impacting the amount of available energy for photosynthesis. Plants sprayed with kaolin particle film have cooler leaf surface temperature and use water more efficiently. The objective of this research was to determine how particle film impacts water relations of two wine grape cultivars when the vines are grown under different amounts of irrigation water. The vines were either sprayed with kaolin or unsprayed (control) and either well-watered or deficit-irrigated. As expected, kaolin reduced leaf temperature under both irrigation regimes. But what was not expected was that irrigation regime had a greater impact on leaf temperature than the presence of particle film. Vine response to particle film was apparent only under well-watered conditions. Better understanding of the mechanism by which kaolin film increases water use efficiency may provide insight to the relative roles of plant hormones and plant water status on leaf gas exchange and the potential for enhancing wine grape production efficiency in arid regions.
Technical Abstract: Kaolin particle film was developed to reduce heat stress and improve water use efficiency in perennial fruit crops. A study was done to determine how the film impacts water relations of wine grape (Vitis vinifera L.) cultivars 'Viognier' and 'Merlot' grown without rootstock in the high desert region of southwestern Idaho. Vines were either sprayed with kaolin or unsprayed (control) and either well-watered at 100% estimated crop evapotranspiration (ETc), or deficit-irrigated at 35% ETc until veraison followed by 70% ETc until harvest. As expected, kaolin reduced leaf temperature under both irrigation regimes. However, a reduction in stomatal conductance and less negative leaf water potential values for kaolin-treated vines were observed only under well-watered conditions. Lack of response to kaolin under deficit water conditions was probably due to a water-stress-induced increase in stomatal closure that was independent of leaf temperature. When leaf temperature difference between kaolin and non-kaolin sprayed leaves was at its daily maximum, deficit-irrigated vines had already reached their minimum or most negative values for stomatal conductance and leaf water potential, but values for well-watered vines had just begun to change. Kaolin had no effect on canopy total light interception, pruning weight, yield, berry titratable acidity or soluble solids concentration, though cluster weight of well-watered, kaolin-sprayed 'Viognier' was larger than well-watered non-kaolin 'Viognier' vines. Better understanding the mechanism by which kaolin film increases water use efficiency may provide insight to the relative roles of plant hormones and plant water status on leaf gas exchange and the potential for enhancing wine grape production efficiency in arid regions.