RESPONSE OF POTTED CALLISTEMON SPECIES TO HIGH SALINITY

     In the recent years nurserymen and landscape architects have shown a renewed and increasing interest for Australian plants, mainly due to the aesthetics characters (abundant flowering with unusual shapes and brilliant colours) and to the adaptability of these species to Mediterranean environmental conditions. The most important Australian species used as ornamentals are included into two big families: Myrtaceae and Proteaceae; among the Myrtaceae, the genus Callistemon, at the moment, is getting a great success as flowering potted plant and as flowering shrub. However, despite it’s increasing diffusion, this genus is still not well known, especially from an ecophysiological point of view. In literature there are no reports on Callistemon’s resistances to abiotic stresses and on the adaptability of the different species to various environments. In the present study we investigated the capacity of Callistemon species to withstand high salinity levels. Experiments were performed at the Department of Crop Biology of the University of Pisa, Italy, during summer-autumn 2002. Plants (90 d-old ) of 11 Callistemon species were grown in pots under four different salinity levels: 6 (control); 50, 100, and 200 mM NaCl during four months. At the end of this period, the resistance to salinity stress was assessed by growth analysis. Results indicated that Callistemon is a highly salt tolerant genus, in fact most of the species, with the exception of C. pityoides, e C. viridiflorus increased their growth in the presence of salt. This was particularly evident in C. pallidus, C. phoeniceus, and, especially, in C. teretifolius, whose growth rate increased proportionally with salinity. The high salt tolerance of Callistemon makes this genus very interesting as an ornamental plant suitable for saline soils and coastal areas.

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