Determination of inorganic ions and organic solutes in plant tissues
The green assimilating branches of H. ammodendron were collected at the five sites in May and July and oven-dried at 70°C for at least 48 h to a constant mass. The dried samples were ground in a ball mill MM400 (Retsch, Germany) into they were uniformly fine powders and freeze dried for preservation. For the extraction of soluble sugar and starch, we followed Anderegg et al., 2012. After the digestion of sucrose and starch, the concentrations of each was measured using the phenol-sulfuric acid method and a UV spectrophotometer (colorimetric method, UV-2401PC, Shimadzu Corporation, Japan). A ninhydrin colorimetric method was used for proline concentration determinations with a UV spectrophotometer (Abraham, Hourton-Cabassa, Erdei, & Szabados, 2010; Song et al., 2006). The Na+concentrations were determined using pulsed flame photometer detection (Song et al., 2006; Jenway Ltd., UK).