Stress-induced variation in leaf gas exchange and chlorophyll a fluorescence in Callistemon plants.

The aim of this research was to evaluate the effect of some abiotic stresses commonly present in the Mediterranean environment (drought, salinity and negative physical soil properties) on a native Australian species (Callistemon citrinus (Curtis) Stapf), as the introduction of species in a new environment is successful, whenever they are able to overcome peculiar stress conditions. Plants were subjected to salinity stress using tap water added with 200 mM NaCl (23.1 mS cm-1), water stress induced by a reduced irrigation of 450 mL/pot/day and root restriction (1.5 L of pot volume instead of 3 L). Results showed that plant growth and total water potential were significantly reduced with all the stress treatments. Net photosynthesis and the other leaf gas exchange parameters were also reduced by stress conditions. Chlorophyll a fluorescence parameters were lower in salt and root-restricted stress conditions, compared to controls. Results suggest that C. citrinus can be used as an ornamental plant in a Mediterranean area, as this species appeared to be particularly resistant to both water stress and root restriction conditions. For this reason, C. citrinus could be chosen in compact soil and limited water availability such as urban environments and gardens with low maintenance.