05/25/05 Water stress - what to know, Pt.1

The concerns about potential water shortages and drought this summer has led to concerns about the potential, and in some cases, survivability of this year's tree fruit crops. Helping understand how trees work might provide insight on what can be done in specific locations and situations. Matt Whiting is a sweet cherry researcher for Washington State University's Prosser Research Station. He says the most water use comes not from water evaporation but in a process called transpiration. That process produces a significant amount of heat. And while the fruit itself is made up of eighty per cent or more water, transpiration is the reason trees need lots of water, especially during drier than normal conditions. WHITING: Essentially what we've got is a scenario where the leaves are in danger of excessive transpiration and in fact, a drought stress or a water stress occurs within a lot of our crops almost every day in July and August where we get high transpiration at the leaf surface. We can't keep up with the demand. Just how much water is needed for transpiration varies on everything from soil to location to sun. But what Whiting and other researchers have discovered through water stress studies is that although water is needed for transpiration, it appears trees don't really need all that much water to not only survive, but to thrive. Answers to the question of water, and when to apply is all covered in future programs.