Smart Vine: Grapevines Adapt to Changing Water Supply
Years of intense research in the arid wine-grape growing region of eastern Washington has taught growers how plants react to various irrigation regimes. Water is such a valuable resource its known as “blue gold,” so this research has been a vital component of growers’ success in producing the fruit that goes into some of the world’s best wines.
But a lot of what is known about how grapevines use water is, so to speak, on the surface. What goes on inside the plant — how vines manage water physiologically — is still somewhat mysterious. That mystery has been one focus of Markus Keller and his graduate students for several years now.
Keller, Chateau Ste. Michelle Distinguished Professor of Viticulture at Washington State University, said that understanding the physiology and biophysics of water are important not only because water is a valuable, bottom-line-affecting input that growers must use, but also because the timing of water application affects vine vigor. “Ultimately,” Keller said, “it’s all about fruit quality. As the winemakers say, a great bottle of wine starts in the vineyard.”
Enter Master of Science student Laura Deyermond, who came to WSU and Washington wine country from Massachusetts. “All I knew about eastern Washington was what I read in Wikipedia,” Deyermond said about her bold leap west. “But I’ve always had an interest in plant physiology and wanted to work on grapes, as it’s my goal to be a vineyard manager and, someday, to own my own vineyard.”
“I came out here to work with Dr. Keller to test certain working assumptions about the balance between grapevine vigor, water use, and fruit growth,” Deyermond said. “We need to understand where that balance point is to ensure sufficient photosynthetic leaf area to ripen fruit and to replenish reserves in the permanent structure of the vine.”
Vigor is a measure of the rate of growth of shoots on a vine. The grower wants a healthy plant but not one so vigorous that it expends energy growing shoots and leaves, called vegetative growth, at the expense of fruit production and ripening. In eastern Washington, vigor is typically controlled by selective application of water. But this method, called regulated deficit irrigation (RDI), could have a deleterious effect called water stress on some vines.
One of the key pruning principles viticulturists are taught is that leaving fewer shoots on a vine results in more vigorous ones. “The working assumption has long been that shoot growth competes with fruit growth — and vines with fewer shoots obviously have less fruit,” Deyermond said. “But in thinking about that, we said, fruit growth doesn’t really start until after flowering when, thanks to RDI and a dry climate, shoot growth is finished. So maybe it’s the ability of the vine to supply water through its hydraulic system that is the limiting factor on vigor.”
Keller said that the hydraulic limitation hypothesis had been tested in trees, but not grapevines. A plant reaches its hydraulic limit when it becomes too tall to pull water to its top against gravity. In order to learn which plants were more vulnerable to water stress, Deyermond went to work with vines of fruit-bearing age, some large and pruned to grow many shoots, some small and pruned to grow only a few shoots.
“Our constant goal is to be able to provide feedback and advice to growers about their vineyard architecture and management,” Keller said. “The question Laura looked at was, are densely planted vineyards, or vineyards that are machine-pruned, more or less susceptible to water stress? The answer to this question will determine whether such vineyards should be irrigated more or less frequently or with different water amounts.”
“What we found but didn’t expect is that larger vines adapted much more than we previously thought they were capable of,” Deyermond said. “They changed their anatomy to move water more efficiently.”
Although the larger vines were indeed somewhat more vulnerable to water stress, they reduced the internal resistance to water flow up the trunk compared with the smaller vines. This enabled them to supply more water to satisfy the demand of their large canopy. And the fruit did have an impact, too: shoots on the small, but not the large, vines continued to grow after flowering despite the use of RDI.
Keller said that plants constantly adjust their internal plumbing to adapt to their size and to the available water supply. “We tend to think of plants as static,” he said, “especially compared to animals, but it turns out they are incredibly smart when it comes to dealing with their resources. Plants manipulate the resource supply and demand much more than we thought.”
by Chelsea Low, with additional reporting by Brian Clark
Read an article about water use in vineyards by Markus Keller in the Spring 2008 issue of the WSU Wine and Grape Research and Extension Newsletter at http://bit.ly/cwPSMu. In the article, Keller makes some recommendations for growers.
Read an article about irrigation research conducted by Keller and his former graduate student, Marco Biondi, in the Feb. 2008 issue of Voice of the Vine: http://bit.ly/gOCW0W.
Tour Argentina and Chile on a Winemakers’ Educational Holiday
Are you interested in tasting Malbac while sitting in a vineyard in Mendoza, Argentina, or tasting a Chilean Cabernet Sauvignon Gran Reserva while visiting with the winemaker? Then you may be interested in the tour WSU has scheduled to Chile and Argentina wineries and vineyards.
The tour will be January 15-28, 2012 and is specially designed for Washington winemakers and grape growers. First we’ll visit the most renowned wine regions surrounding Santiago: Maipo Valley, Colchagua Valley, Aconcagua Valley and Casablanca Valley. Then we’ll fly over the Andes to visit the Mendoza wine region in Argentina.
Free time will allow you to explore the cities of Santiago and Mendoza, the beach at Valparaiso and a resort in the Andes. If you are interested in learning more about this opportunity, please contact Theresa Beaver at tbeaver@wsu.edu.
Theresa Beaver is the coordinator for WSU’s professional certificate programs in viticulture and enology; learn more about these professional development programs at http://bit.ly/di2wYd.
Read “The Mendoza Connection” in Voice of the Vine at http://bit.ly/fx0WGN.
Walter Clore Wine and Culinary Center Receives EDA Grant Award
The Walter Clore Wine and Culinary Center and the Port of Benton were awarded a $2 million grant by the U.S. Economic Development Administration for the construction of the $4 million agri-tourism and education center. The building design process will begin immediately with construction scheduled for 2012.
The site in Prosser was chosen for the Clore Center because of Prosser’s distinction as the home of the WSU Irrigated Agriculture Research and Extension Center, the largest irrigated agricultural research center in the United States. The center is named for the late Dr. Walter J. Clore who was based in Prosser and, in 1937, began his research on small fruits, vegetables and wine grapes there. Clore is remembered as the father of the Washington wine industry, a title officially bestowed upon him by the Washington legislature in 2001.
Through a joint operating agreement, the Port of Benton will oversee construction and own the building. The Clore Center, a non-profit organization, will operate the center to promote the quality and diversity of Washington wine and food through education and hands-on experiences.
Designed to complement its natural surroundings, the 15,000 square foot building and grounds will offer several indoor and outdoor venues, including a tasting room, demonstration kitchen, agriculture and viticulture exhibits, classrooms, conference rooms, office space, a retail shop, instructional vineyards, interpretive and production gardens and a walkway along the Yakima River.
According to a spokesperson for the Clore Center, the center is expected to have a positive impact on Washington’s wine and agricultural industries through education, increased product and brand awareness, and jobs creation, resulting in stronger economies for agriculture-based communities across the state. Increased product demand is expected to result in the creation of 69 direct jobs in the wine industry and additional indirect jobs in the wine and agriculture sectors within a five-year period.
Visit the Clore Center web site at http://bit.ly/wclore. Learn more about Walt Clore and the history of Washington wine on the WSU viticulture and enology web site: http://bit.ly/winehistory.