Essentially all the controlled-climate research with grapevines in California has been done in the past 20 years. A stationary and a rotating phytotron unit became available in 1961 and 1965, respectively, for plant research at the University of California, Davis. The phytotron rooms precisely control day and night temperatures as well as humidity. Solar radiation is the source of light and can be controlled to some extent with shade fabrics, filters, and the like. More recently, large temperature-controlled water baths have been added to the rooms so that root and air temperatures can be varied independently of each other and their interaction studied.