Diurnal Changes in Stem Diameter Depend Upon Variations in Water Content: Direct Evidence in Peach Trees

Three to five-year-old peach trees (Prunus persica (L.) Batsch cv. 'Maycrest') grafted on P. 'Damas J869' grown in a sand t were removed in the spring and grown hydroponically for several months. The ~ystem comprised two balances continuousl) recording the mass of the nutrient solution and that of the iree, so as to estimate transpiration and water uptake rates sepa Diurnal variation in plant water content (transpiration minus water uptake) was observed, with rapidly decreasing values w the solar radiation increased, while the reverse occurred when radiation decreased. Changes in stem diameter were continuo recorded using linear variable differential transducers. Data collected over several days of contrasting climatic conditions re that rapid changes in the stem diameter occurred throughout the day and were closely related to plant water content. A lag not exceeding 10 min was found between changes in stem diameter and plant water content. These results are discussed in r to the use of micromorphometric methods to control irrigation in fruit trees. Moreover. we give values for the water stored shoots which may contribute to the transpiration stream.