Experimental and Theoretical Study of the Effects of Rare Earth Elements on Growth and Chlorophyll of Alfalfa (Medicago sativa L.) Seedling

Abstract

Rare earth elements (REEs) of low concentration are usually beneficial to plant growth, while they are toxic at high concentrations. The effects of treatment with lanthanum (La) (10 and 20 μM), cerium (Ce) (10 and 20 μM), and terbium (Tb) (10 and 20 μM) on seedling growth of alfalfa (Medicago sativa L.), which is one of the most important perennial leguminous forages in the world, were studied. The results showed that all three REE treatments quickened the germination of seeds. The length of shoot under La (20 μM) treatment was significantly shortened (P < 0.05). In addition, treatment with La, Ce, and Tb had a “hormesis effect” on root length. There was a significant decrease in chlorophyll content on treatment with the three REEs, and the degree of decline was in the order of La < Ce < Tb, under the same concentration. In vitro experiments and quantum chemical calculations were further performed to explain why the treatments with REEs reduced the chlorophyll content. In vitro experiments showed that La, Ce, and Tb treatments reduced the absorbance of chlorophyll, and the decrease followed in the order of La > Ce > Tb. Quantum chemical calculations predicted that the decrease in absorption intensity was caused by the reactions between La, Ce, Tb, and chlorophyll, which formed lanthanides-chlorophyll; and there were five types of stable lanthanides-chlorophyll. In conclusion, the decrease in chlorophyll content on treatment with REEs was caused by the change in chlorophyll structure.

CeO2NP priming enhances the seed vigor of alfalfa (Medicago sativa) under salt stress

“…Salt (NaCl) solutions with different concentrations (0, 50, 100, 150, 200, and 250 mM) were established to conduct germination experiments to characterize the effects of salt concentration. Referring to the processing method of Song et al. (2021) , all seeds used for the germination experiment were disinfected with 75% alcohol for 30 s and washed five times with sterile water.…”

Evaluate the effects of rare earth elements on sweet pepper seeds germination process, seedlings growth and plants productivity

“…Current results also showed that Nd at high concentrations could induce seedlings , growth including the number of leaves per seedling (NL/S), fresh weight (SFW), and dry weight (SDW). It was reported that REEs treatment including Nd at appropriate concentration can promote seedlings , root growth and activity which considers the main organ that absorbs water and nutrients due to the vigor of seedlings , growth [52][53][54]. The extent of variation for chlorophyll Fig.…”

“…3 over control treatment. The positive effects of REEs on pepper plant growth may be returned to the fact that using a suitable concentration of REEs could stimulate plant growth and development because they have similar physiological effects as some mineral nutrients [54][55] in additive; REEs stimulate the photosynthetic capacity [56]. It was reported that neodymium (Nd) is an effective fertilizer for improving plant nutrition and healthy growth [38], significantly promotes growth, increases the chlorophyll content, and accelerates the photosynthesis rate and accumulation of organic substances, thereby enhancing plant fresh and dry mass [57][58].…”

“…As shown in the current study that REEs were induce pepper chlorophyll leaf content, it possibility may return that most of the REEs adhered to the cell wall [60] or bound to the cell membrane [61], and the free radical reaction was in equilibrium [62], which increased the stability of the membrane [63] and activity of the corresponding enzyme [64], thus stimulating and compensating the chlorophyll content. Furthermore, [54] deduced that the change in chlorophyll leaf content was caused by two reasons the change in total chlorophyll content, and the change in chlorophyll structure so, significant changes were observed in the chlorophyll content in plant leaves under different concentrations of REEs. The REE application can have a beneficial effect by improving the growth, height, and dry weight of plants when supplied in an appropriate concentration [65] and [38].…”

Neodymium Nitrate Improves the Germination of Aged Wheat Seeds by Increasing Soluble Substances and Activating Antioxidative and Metabolic Enzymes in Seeds

“…Exogenous melatonin may increase the germination percentage of wheat seeds by increasing the activity of antioxidant protective enzymes [23]. Some experiments indicate that treatment with rare-earth elements increases the germination percentage and vigor [20,[24][25][26][27][28]. Lanthanum and cerium are currently mainly used in agricultural production.…”