Preliminary assesment of ABA concentration in roots of drip irrigated peach trees

Abscisic acid (ABA) is a phytohormone able to regulate the stomatal behaviour, transpiration and photosynthesis. ABA synthesis is usually associated to drought conditions. Based on the evidence that drip irrigation wets only 15-20% of soil surface and that 80% is dry during summer, this study tests the hypothesis that in a well drip irrigated tree the ABA concentration in roots located in the inter-row (non-irrigated) is higher than that measured in roots under the emitter line (irrigated row). Abscisic acid was determined by a competitive enzyme-linked immunosorbent assay in roots collected from a well irrigated tree (x 3) in summer at row and inter-row positions in a nectarine orchard grown in Southern Italy. Results show that leaf water potential was optimal (0.3 MPa at pre-dawn). However, ABA concentration was 3.74 pmol g-1 FW in roots from inter-row while it was 2.58 pmol g-1 FW in that growing along the row. Possible effects of the increased ABA levels at a part of the root-zone on leaf gas exchanges are discussed.