The Physiological Response of Different Brook Willow (Salix acmophylla Boiss.) Ecotypes to Salinity

Abstract

Few phytoremediation studies have been conducted under semi-arid conditions where plants are subjected to drought and/or salinity stress. Although the genus Salix is frequently used in phytoremediation, information regarding its tolerance of drought and salinity is limited. In the present study, Salix acmophylla Boiss. cuttings from three sites (Adom, Darom and Mea She’arim) were tested for tolerance to salinity stress by growing them hydroponically under either control or increasing NaCl concentrations corresponding to electrical conductivities of 3 and 6 dS m−1 in a 42-day greenhouse trial. Gas exchange parameters, chlorophyll fluorescence and concentration, and water-use efficiency were measured weekly and biomass was collected at the end of the trial. Root, leaf and stem productivity was significantly reduced in the Adom ecotype, suggesting that Darom and Mea She’arim are the more salt-tolerant of the three ecotypes. Net assimilation and stomatal conductance rates in salt-treated Adom were significantly reduced by the last week of the trial, coinciding with reduced intrinsic water use efficiency and chlorophyll a content and greater stomatal aperture. In contrast, early reductions in stomatal conductance and stomatal aperture in Darom and Mea She’arim stabilized, together with pigment concentrations, especially carotenoids. These results suggest that Darom and Mea She’arim are more tolerant to salt than Adom, and provide further phenotypic support to the recently published data demonstrating their genetic similarities and their usefulness in phytoremediation under saline conditions.

Protocol for In Vitro Propagation of Salix acmophylla (Boiss.). Studies on Three Ecotypes

“…S. acmophylla is also grown on about 40 ha on specialized farms in Israel for ritual use in the Jewish harvest festival of Sukkot (Leviticus 23:40). The species has been studied for its potential use in phytoremediation [35,36] in semi-arid climates, given its wide-ranging natural distribution and its demonstrated tolerance to heavy metals and salinity [37]. Recently, S. acmophylla irrigated with pre-treated municipal wastewater was successfully used as green fodder for goats, providing specific chemicals that have high potential value in maintaining animal health [38,39].…”