Zeolite and attapoulgite foliar applications improve the photosynthetic performance of ‘Muscat Hamburg’ grapevines

Climate change has significantly altered weather patterns, with elevated temperatures and heatwaves emerging as major environmental challenges for viticulture. High temperatures can negatively affect grapevine growth, maturity, and overall quality. In response to these challenges, there is an increasing interest in sustainable, cost-effective mitigation strategies that reduce reliance on chemical inputs. In this study, an open-field experiment was conducted to assess the effects of foliar applications of zeolite and attapulgite on the grapevine cultivar ‘Muscat Hamburg’ under the Mediterranean conditions in Central Greece. The experiment followed a randomized complete block design with three treatments (control, zeolite applied at 4% w/v, and attapulgite applied at 4% w/v) and five replications. The application of these chemically inert mineral particles significantly decreased leaf temperature and enhanced physiological performance in veraison and maturity stages, particularly at midday. Specifically, stomatal conductance (g_s), transpiration rate (E), and the net photosynthetic rate (A) were significantly increased compared to the control. Regarding yield components, foliar applications did not significantly affect yield per vine, number of clusters per vine, cluster width and length, or the berries' weight. However, attapulgite application led to a significant increase in cluster weight, cluster density, and number of berries per cluster. Additionally, both zeolite and attapulgite significantly increased the relative skin mass. In terms of grape quality traits, total acidity (TA) was not affected by foliar applications, although attapulgite significantly increased must pH, while zeolite application led to a reduction in total soluble solids (TSSs). In conclusion, foliar applications of zeolite and attapulgite can be integrated into sustainable viticultural practices to mitigate the adverse effects of high temperatures. By reducing leaf temperature and improving physiological performance, these treatments contribute to the protection of grapevines under heat stress conditions.