A WHOLE-TREE SYSTEM FOR GAS-EXCHANGE STUDIES

Based on a commercially available net photosynthesis (Pn) unit coupled to a custom-built chamber that does not require air conditioning, a low-cost system to measure whole-tree gas exchange in the field is described. The temperature in the chamber is influenced by air flow in relation to tree size. A flow of 20 liters.s-1 (equal to almost-equal-to 1.5 chamber volume changes/min) was sufficient to maintain the leaves of an 11-year-old 'Golden Delicious'/M.27 tree at a temperature similar to that of the ambient air and control CO2 gradients in the chamber. The system has been in operation on apple (Malus domestica Borkh.) trees for up to 4 months without modifying tree behavior.