To study stomatal conductance at different leaf positions and xylem flow rate at different depths in the apple branch

Abstract

The influence of leaf position (age) on the shoot on stomatal conductance and depth on xylem flow rate in apples (Malus pumila) MM106 cv. Gala branches were studied at Lincoln University, Canterbury, New Zealand. Leaf position on the shoot had significant effect on the stomatal conductance. Old leaves had a higher stomatal conductance (gs) 0.53 (mol H₂O m⁻² s⁻¹ day⁻¹ followed fully expanded new leaves with 0.48 (mol H₂O m⁻² s⁻¹ day⁻¹ as compared to that for new (not fully expanded) leaves which was 0.20 (mol H₂O m⁻² s⁻¹ day⁻¹. However, the apical positions exhibited rapid changes in gs while the intermediate leaves exhibited somewhat uniform changes in gs through out the day. A progressive decrease in xylem flow was measured across the branches of apple trees. The highest xylem flow was at 7.5mm depth from the surface of bark.