05/27/05 Water stress - what to know, Finale

Washington State University tree fruit research scientist Matt Whiting will be the first to say researchers don't have all the answers as to how best to maximum water use to produce maximum size, yield, and quality in tree fruit. But with a potential drought looming in much of the tree fruit region, Whiting and others are using what they have learned so far in water deficit and water stress studies to help growers make informed decisions. One possible conclusion is even though trees need water mostly for the transpiration process, they don't need as much water as one would think. But with so many variables to consider, Whiting says each tree and each area has a different threshold mark. But he may have an answer as to when the water has to go on, in relationship to the critical time of fruit expansion and development. Whiting studied water effects through his research specialty of sweet cherries. And in studying water application or lack there off during various developmental stages, water stress will not affect budding, flower induction, bloom, or cell division significantly. Whiting says the key is cell expansion, or turgor. WHITING: This is the point where any loss in turgor is going to reduce the driving force, the potential to expand, the fruit or growth rates, and so, this is the one development stage that I would key on. Meaning cell development is the time the fruit is most susceptible to water stress. Yet Whiting points out as a side note that in sweet cherry trials at W.S.U.  Prosser, where only half the water used was applied to trees in the trial plot, there was not signs of any reduction in fruit growth rates.