The use of La³⁺ to reduce photosynthesis damage under P-deficiency was examined. We confirmed that La³⁺ increased the level of antioxidant protective enzymes, including superoxide dismutase (SOD) and peroxidase (POD), while it significantly decreased malondialdehyde (MDA) content. Root hydraulic conductivity (Lp) was also examined to elucidate the role of La³⁺ in the relationship between water and nutrition transport. Treatment of young seedlings with La³⁺ at 150 mg L⁻¹ effectively improved PUE in roots, stems, and leaves via the regulation of root elongation and activation of root physiological responses to P-deficiency, e.g., root activity and acid phosphatase (APase) activity.
La³⁺ substantially alleviated P-deficiency symptoms. Here, we examined the effects of La³⁺ on growth, photosynthetic ability, and phosphorus-use efficiency (PUE) in various organs of adzuki bean (Vigna angularis) seedlings. We conclude that there was insufficient evidence to recommend the use of La (screened from a range of REEs as the most promising) to increase annual dry matter yield or decrease Cd uptake from ryegrass-dominated pastures.
Decreases in the Cd concentration of ryegrass (mgkg-1) only occurred in the harvests after application (40% at 20kg La ha-1 for one soil) and did not translate into an annual effect. A similarly mixed yield response occurred in a field trial. From a range of REEs applied to ryegrass with and without N, lanthanum (La) showed minor yield improvement under glasshouse conditions, but only for Sedimentary (not Volcanic) soils low in REE concentration and at 40% available soil moisture or less.
A soil survey measuring REEs concentrations in soils from across New Zealand showed that REEs were enriched in Volcanic compared with Sedimentary-derived soils, and in soils used for dairying compared with those used for sheep and beef. We hypothesised that under the right soil and climatic conditions the application REEs to soil may improve yield of ryegrass-dominated pasture and inhibit Cd uptake in foliage. Rare earth elements (REEs) have been linked to increases and decreases in plant growth and the uptake of biotoxic metals such as Cadmium (Cd).
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