Early response of <i>Falcataria falcata</i> L. Greuter &amp; R.Rankin seedlings to iron exposure in water media: implications for revegetation of degraded land

One of the challenges in post-mining land is the acidic soil and high iron (Fe) content. This study aims to analyze the response and effects of Fe exposure on the early growth of Falcataria falcata seedlings and to determine the threshold of F. falcata to Fe exposure. This study used a completely randomized design with Fe concentration treatments of 9 levels (0, 0.25, 0.5, 0.75, 1, 1.25, 1.5, 1.75, and 2 mM). The parameters observed included height, root length, dry weight of roots and shoots, total dry weight, tolerance index, chlorophyll pigment content, and MDA lipid peroxide content. The results showed that Fe exposure significantly affected all growth parameters. Fe concentrations of 0.25–0.75 mM increased growth, while concentrations of 1–2 mM decreased the growth of F. falcata seedlings. The tolerance index also increased when exposed to 0.25–0.75 mM Fe and decreased to 1–2 mM Fe. Fe exposure significantly affected chlorophyll a, b and total chlorophyll content. An increased Fe concentration of 1.5–2 mM reduced the chlorophyll pigment content of F. falcata seedlings. Fe exposure increased the MDA lipid peroxide content of F. falcata seedlings, peaking at 1.5 mM Fe exposure, which caused a very significant increase. Fe concentrations up to 0.75 mM were the threshold for F. falcata exposure to Fe, and further increases in Fe exposure had negative and potentially toxic effects. F. falcata could be one species used to rehabilitate degraded land, especially land with intermediate Fe Fe consentrations.