Productivity of Peach Trees : Tree Growth and Water Stress in Relation to Fruit Growth and Assimilate Demand

The growth of the limbs of peach trees measured by dendrometerswas inhibited during periods when the rate of d. wt accumulationby the fruit was increasing. The diurnal shrinkage of theselimbs measured by the same dendrometers was greatest duringperiods when limb growth was inhibited. The increase in diurnalshrinkage of the limbs coinciding with inhibited limb growth,and increased assimilate demand, was greater than that causedby environmental factors at maximum soil water-potential andgreater than that caused by five days soil drying after irrigation.Leaf water potential and diurnal limb shrinkage were measuredcontinuously during two periods of maximum soil water-potentialand leaf area when the rate of d. wt increase of the fruit wasdecreasing (DW II) and then later when the rate of d. wt increaseof the fruit was increasing (DW III). The leaf water potentialwas lower and limb shrinkage greater during DW 111 than DW II.The hydraulic gradient also increased from 1 bar m^–1 inDW II to 2 bar m^–1 in DW III Environmental conditions during both periods were very similarand the data suggest total water use by the tree increased substantiallyduring periods of high assimilate demand by the fruit.