Grapes at Work

Our grapes are up to something we never suspected. You know those leaves on grape plants?

Grape Leaves Waiting for the Light

Assmannshausen am Rhein, late June, 6 a.m.

Photosynthesis is the process by which plants convert sunlight, carbon dioxide and water into usuable (and storable) energy. There are, however, a number of different photosynthetic processes, discovered by different types of plants in different ages of the world. Grapes belong to the oldest group of photosynthesizers, which steal energy from hydrogen in a two part process involving complex sugars. Plants of this type lose 95% of their water to evaporation. There is another group of plants, far less ancient, which evolved to live in extremely hot, dry climates. They breathe at night, convert their carbon into an intermediary compound, and complete their photosynthesis in the sunlight, without needing to breathe. Through this process, they maintain most of their water. They include the sedums and many succulents, including…

Never Underestimate a Prickly Pear Cactus

One of the joys of the North Okanagan climate is the way in which hot climate plants such as cacti have found dry microclimates in what might otherwise be just too wet. When you’re a cactus, it’s not just about the desert.

They do not include grape plants, but they do include grape skins. Grape skins have the ability not only to photosynthesize normally during the day, under certain conditions, but at other times to accumulate carbon from the air on cool fall nights, and then to close their pores during the day and photosynthesize their stored carbon. What does this mean? No one knows, but it does seem prudent to work on the principle that the next time a winemaker tells you that hot days are necessarily lost to wine production, because normal photosynthesis shuts down in the heat, or that cool nights have no effect on grapes, because photosynthesis is shut down, well, believe the winemakers of 200 years ago instead, who insisted that it matters. It does.

Dancing with Pinot Noir in Okanagan Falls

While the grapes are doing one thing, the leaves are doing another. These old leaves at the base of the vines are no longer photosynthesizing. The assumption is that they are no longer productive. This may not be true. No one knows. Grapes and cactii, though. Partners in adaptation. Who knew.

One recent study has shown that grape leaves are capable of absorbing 25% more sunlight than normal leaves, without radiating it off as heat or shutting down. When you factor in the curious chemistry of grapes, which are laid down as acid, which is then replaced with sugars, and consider that on the surface of this transformation all the complex flavours of grapes are laid down in reaction with a completely different photosynthetic process that seems capable of dealing with both shade and darkness, independently of the leaves and right at the intersection with a complex ecosystem of yeasts, fungi and bacteria on the skin of the grapes, well, maybe you’ll start getting excited too.

 Chopaka Gewürztraminir. 1995.

Back in the day when you could make the best wines in the valley at home. Seven Stones Winery owns these vines now. Drat.

I hope so. It is always beautiful to learn how little we know and how processes deemed simple and mechanical just aren’t. Go, grapes, go!

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