Climate change has people worrying about a lot of things, not least how it’ll affect their favorite treats. Will rising temperatures mean less chocolate or coffee? What about wine? A small comfort is that some grapes have the ability the conserve water, and scientists have been learning more about which ones.
Grapevines have pores on their leaves called stomata, which take up carbon dioxide that the plants need for photosynthesis to create the sugars the grapes need to grow. Stomata also release water vapor and other gasses such as oxygen. One way that grapevines can conserve water is to close their stomata to prevent this evaporation. Scientists wanted to test their hunch that grapevines grown in hot, dry climates would keep their stomata closed more often than grapevines grown in cooler and more humid regions.
They examined 34 varieties of grapes and used a database of different wine regions to see if there were associations between the grape varieties and regions. Their study found that, sure enough, grapes grown in hotter, drier regions, such as Sangiovese, which are typically grown in Italy’s Tuscany, keep their stomata closed more often than grapes such as Sauvignon blanc, which are typically grown in the milder Bordeaux region of France.
Does that mean if the climate keeps getting hotter, grapevines can just keep their stomata closed more often? As you might have guessed, there’s a limit. Grapevines use evaporation to cool themselves down, and if the plants restrict evaporation too much, they won’t be able to photosynthesize properly. It’s all a fine balance, much like a perfect bottle of wine.