Vol. 85 No: 1

Title:
Differences in growth and ornamental parameters between young Chamaerops humilis L. and Washingtonia robusta H.Wendl palm trees in response to salinity

Authors:
M.D. SIMÓN, M. NIEVES-CORDONES and M. NIEVES

pp: 7-11

Abstract:
Chamaerops humilis L. and Washingtonia robusta H.Wendl trees represent two ornamental palms which differ in size and water use, the result of which may confer contrasting responses to salinity. Two-year-old plants (112 per species) were grown over two additional years with irrigation water having an electrical conductivity (ECw) of 2, 4, 6, or 8 dS m^-1, and were harvested in seven successive harvests. The saline treatments had a statistically significant linear effect upon the reduction in relative biomass yield. The threshold and slope values were: 2.7 dS m^-1 and 7.0% dS^-1 m for C. humilis; and 3.3 dS m^-1 and 9.5% dS^-1 m for W. robusta. There were no significant differences in the levels of toxic ions in the leaves of W. robusta between the 2 – 8 dS m^-1 treatments. In contrast, the levels of toxic ions increased significantly in the leaves of C. humilis. The results suggest that W. robusta is more sensitive to osmotic stress than C. humilis. This may be the cause of the steeper slope of the salt-tolerance equation for W. robusta. There were significant reductions in plant height and in leaf area at an EC of 8 dS m^-1, but these effects were more marked in W. robusta. This species also suffered significantly reduced numbers of leaves in saline treatments at 6 or 8 dS m^-1.We conclude that both young palm tree species can be classified as moderately tolerant to salinity. However, at high saline levels, a drought-tolerant palm such as C. humilis is more salt-tolerant than W. robusta. It would be appropriate to water 3-year-old palms with water having an ECw of 2 dS m^-1, and with water at 4 dS m^-1 in the following year.

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