TRANSPIRATION RATE OF PRUNUS-AVIUM L SEEDLINGS INSIDE AN UNVENTILATEDTREE SHELTER

Transpiration rate was measured on one-year-old sheltered and control non sheltered Prunus avium L. seedlings using the stem heat balance me thod. The sheltered trees, protected by unventilated 2.1-m-tall plasti c tubes, had an average transpiration rate 6 times less than control t rees, although the leaves had a high conductance throughout the day. L ower transpiration rates in shelters may be explained by low values of net radiation, extremely small water vapour deficit, and low windspee d resulting in a high boundary layer resistance to water transfer. Con sequences of such low transpiration are discussed, and recommendations regarding the optimal use of treeshelters are deduced. The removal or sudden ventilation of a treeshelter during the growing season should be avoided, and weeding the sheltered trees is essential. (C) 1997 Els evier Science B.V.