Abstract

Climate changes may cause severe impacts both on grapevine and berry development. Foliar application of kaolin has been suggested as a mitigation strategy to cope with stress caused by excessive heat/radiation absorbed by leaves and grape berry clusters. However, its effect on the light micro-environment inside the canopy and clusters, as well as on the acclimation status and physiological responses of the grape berries, is unclear. The main objective of this work was to evaluate the effect of foliar kaolin application on the photosynthetic activity of the exocarp and seeds, which are the main photosynthetically active berry tissues. For this purpose, berries from high light (HL) and low light (LL) microclimates in the canopy, from kaolin-treated and non-treated, irrigated and non-irrigated plants, were collected at three developmental stages. Photochemical and non-photochemical efficiencies of both tissues were obtained by a pulse amplitude modulated chlorophyll fluorescence imaging analysis. The maximum quantum efficiency (Fv/Fm) data for green HL-grown berries suggest that kaolin application can protect the berry exocarp from light stress. At the mature stage, exocarps of LL grapes from irrigated plants treated with kaolin presented higher Fv/Fm and relative electron transport rates (rETR200) than those without kaolin. However, for the seeds, a negative interaction between kaolin and irrigation were observed especially in HL grapes. These results highlight the impact of foliar kaolin application on the photosynthetic performance of grape berries growing under different light microclimates and irrigation regimes, throughout the season. This provides insights for a more case-oriented application of this mitigation strategy on grapevines.

Highlights

  • Viticulture is a historically important agronomic and socio-economic sector in Portugal

  • The main objective of the present work was to evaluate the effects of foliar kaolin application on the photosynthetic activity of grape berry tissues from clusters growing at two distinct microclimates, which include high light (HL) and low light (LL) microclimates, of irrigated and non-irrigated grapevines, during the season

  • Notation with an asterisk means that only one factor was significant

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Summary

Introduction

Viticulture is a historically important agronomic and socio-economic sector in Portugal. Grapevine is influenced by a complex and interacting system commonly called terroir, which, according to the OIV [3], includes specific soil, topography, climate, landscape characteristics and biodiversity features, and interaction with applied vitivini-cultural practices. This complex system influences the canopy microclimate and grapevine physiology and development and, grape berry quality and the organoleptic properties of its wine, which is typical of each region. Climate change projections point to a pronounced temperature variation, with an overall increase of up to 3.7 ◦ C by the end of this century, compared to the 1985–2005 reference period [4] These temperature changes will have great impacts in the Mediterranean wine regions [5]

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