Paclobutrazol Influences Salinity Responses of Peach and Olive

Abstract

We studied the effect of a 200-mg·liter–1 foliar application of paclobutrazol (PBZ) on growth and physiological responses of Prunus persica `Nemaguard' (salt-sensitive) and Olea europea `Manzanillo' (salt-tolerant) to salt stress. One-year-old trees were grown in 3 sand: 3 field soil: 4 pine bark media in 20-cm pots in a greenhouse and were irrigated with nutrient solutions adjusted with 0, 9, 18, or 36 mmol NaCl for peach and 0, 36, 72, 108 mmol NaCI for olive. Dry weight, photosynthesis, and leaf conductance decreased with increasing salinity for both species. However, leaf expansion rate was unaffected by NaCl. PBZ reduced dry weight for peach only, but PBZ increased photosynthesis and reduced leaf expansion rate for both species. Relative water content was decreased by salt but increased by PBZ. PBZ reduced the foliar Na and Cl content in peach but not olive. Olive had less Na in leaves than peach at 36 mmol NaCI, accumulated less C in leaves in all salt treatments, and had higher foliar Na without symptom expression. PBZ may reduce salt stress in sensitive species like peach by reducing foliar Na and Cl accumulation but has less influence on the salinity response of the more salt-tolerant olive.