The Application of an Antitranspirant to Grape Bunches Affects the Composition of Primary and Specialized Metabolites Related to Berry Quality

High Resolution Image Download MS PowerPoint Slide Climate change accelerates grape ripening, with bunch transpiration contributing to faster sugar accumulation. This study aimed to determine how bunch transpiration influences the response of grape primary and specialized metabolites to projected temperature and relative humidity (RH) changes. Fruit-bearing cuttings of cv. Tempranillo grew in greenhouses under two conditions: 24/14 °C with 55/70% RH (T) and 28/18 °C with 43/58% (T+4). At veraison, T+4 plants were split into untreated and antitranspirant-treated (AT+4) groups. T+4 reduced amino acids, anthocyanins, and hydroxycinnamic acids while increasing acylated anthocyanins as well as caftaric acid abundance. AT+4 further decreased amino acids, notably proline and aroma precursors, as well as yeast-assimilable nitrogen, and amplified the T+4-driven decline in anthocyanins. Under elevated temperature and low RH, reducing transpiration alters berry composition, highlighting berry transpiration as a critical mechanism for maintaining metabolic balance in warming climates. Factors related to the antitranspirant application may have contributed to these observed changes.