Jeff Glorfeld
Jeff Glorfeld is a former senior editor of The Age newspaper in Australia, and is now a freelance journalist based in California, US.
A new study that describes grapevines as “crops of global economic importance” which “will face increasing drought stress” because many varieties are highly vulnerable to diminished water supplies caused by the rising incidence and severity of seasonal droughts, nevertheless disputes previous claims that many grape-growing regions – including some of the most famous – will fail because of climate change.
The report, published in the journal Science Advances, details long-term observations from California’s Napa Valley region in the US and from the iconic Bordeaux region in France, and concludes that “grapevines never reach their lethal water-potential thresholds under seasonal droughts”.
The researchers, led by Guillaume Charrier from the French National Institute for Agricultural Research, say the grapevines they evaluated were not at risk of dying from even very dry conditions because they never experienced a full collapse of their water transport systems, known as hydraulic failure. Even in drought they retained their ability to move water from the roots to the stems and leaves.
The findings in this latest study are in stark contrast to a recent report that said wine-grape production in some of the world’s most beloved regions, including Bordeaux, Cotes du Rhone and Burgundy, was doomed by climate change.{%recommended 1512%}
Water availability is one of the most important factors in determining plant survival and productivity, the new report says, noting that agriculture accounts for 80% of all fresh water used in California. “Thus, reducing crop water use is essential to increase agricultural sustainability,” the researchers state.
It report also acknowledges the need to reduce water use, in light of “the increased likelihood of large-scale water deficits and extreme drought events”, which “is driving the search for more drought-resistant crops”.
With this in mind, the researchers set out to more fully understand how grape vines manage water supplies during periods of long-term drought. Over a decade, using field observations and greenhouse experiments, they studied water regulation in common Vitis vinifera varieties, which account for most of world’s wine production.
They found that regulation of water in the stoma – pores in the leaves through which plants “breathe” and pass water vapour – as well as blockage of water transportation because of air bubbles (a process known as embolism), was similar across all V. vinifera varieties.
However, they found that a grapevine’s vulnerability to embolism actually decreases as stress increases, which suggests that drought-induced embolism should be uncommon.
Charrier believes the research can help viticulturists better manage their irrigation strategies, to save water and money.
