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Stuck on You

by Andrew McNaughton

A good grafter, at least in the UK, would indicate someone was willing to work hard and put in a decent day’s work. When you move to the world of plants, a ‘good grafter’ takes on a more specific meaning. Grafting is a case of having your cake and eating it. Often plants are bred for desirable characteristics, and plant breeding over the last 1,000 years or so has refined this to a fine art. The problem is a plant breeder might have produced a grape with perfect ripening characteristics, but with a root system which would make a radish blush. Grafting of human body parts requires brutal immuno-supressant drugs to have even a reasonable chance of working. Plants on the other hand are a lot more accommodating with a wide range of scions (above ground variety) being able to be grafted to any one stock plant (root system).

Usually a grape variety would be grafted onto a root stock because it provides an improvement in growth and grape production. This could be due to better nutrient uptake or simply being better suited to local conditions. Varieties of
Vitis vinifera native to North America are resistant to local soil-borne  pests, but tend to produce wine unsuited to the European palette. The solution is to graft European grape varieties onto native North American root stocks. Grafting won’t however solve all incompatibilities between environment and grape. Vintners in Oregon had little success with Chardonnay grapes imported from California, irrespective of how they grafted them to local root stocks. The scions were unsuited to the colder Oregon conditions and failed to thrive. Whereas imports from Burgundy, which has a closer match in climate, did.

Plants produce their water and nutrient conducting vessels at their vascular cambium layers, a ring of actively propagating cells which ring their stems. Leaving old cells behind them and generating new cells in front. Seen as growth rings in trees when sawn down. For a grant to ‘take’, both the plants’ vascular cambiums must come into close contact. This is the function of the variety of grafts used by horticulturalists, to provide a continuous water and nutrient conducting network between the stock and scion plants - plus a strong mechanical connection.

Plant Graft Types

Plants also have a complex network of plasmodesmata running throughout them. These are essentially tiny finger-like projections of their cell membranes which poke through neighbouring cell walls. The result is a continuous cellular network. It is through this network the stock and scion plants ‘communicate’ and explains why maturation can be dramatically sped up by grafting young scions to mature stock plants. The latter triggering early maturation in the former by the transmission of its phyto-hormones (plant hormones). The partners in the graft will have intermingling of their plasmodesmata, each snaking through the other's cell walls. There is also evidence of direct connection between them, as evidenced by the transmission of phytohormones and the like. There’s more going on in your grafted vines than you might think when you start looking at their phyto-hormones. So, if your wine seems particularly hard to understand, perhaps unreasonably sharp - maybe it's a victim of another plant's PMT?

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