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Item Management of Iron and Manganese Toxicities of Lentil Crops Grown in Central ChileAutores: Amigo, Ramón; Méndez-Espinoza, Ana María; Schwember, Andrés R.; Cornejo , Jorge; Baettig , Ricardo; Cabeza, Ricardo A.Iron (Fe) and manganese (Mn) toxicity is a widespread problem in lentil production in the coastal dryland of Chile. Increasing the soil pH by liming with CaCO3 or incrementing grain yields through nitrogen fertilization can help the plants to reduce metal concentration. Thus, the main objective of this work was to evaluate two different fertilization strategies (lime (CaCO3) and nitrogen (N) additions) to reduce Fe and Mn toxicities in lentils. Lentils grown under field conditions with the highest Fe and Mn concentrations showed toxicity symptoms, but without grain yield reductions. In a pot experiment using the same soil as in the field with toxicity symptoms, the dry matter (DM) produced at the end of the trial was higher in the plants that received N while the lowest DM production was recorded in those plants treated with lime. In particular, higher root DM sustained the growth of the N-fertilized shoots, which also positively affected the grain yields being 33% higher than the control treatment (no fertilization addition). In the plants fertilized with N, the Fe and Mn levels in the shoots were lower than the control plants and those grown in soils treated with lime, but showed higher concentrations of Fe and Mn in roots. In parallel, roots exhibited high concentrations of Fe and Mn that were 13- and 9-fold higher than in the shoots. Additionally, a significant decrease of 29% in Mn concentration in the grains of plants treated with N was reported. Overall, our results suggest that an increase in DM of lentils by the addition of N can reduce the Mn concentration on leaves to a level that is likely under the threshold that causes toxicity in plant tissues. Finally, we conclude that the increase of Fe and Mn in the roots may be connected to the reduction of these metals on leaves.Item The inhibition of N 2 fixation by nitrogen is attenuated by the P supply, altering the plant metabolismAutores: Cabeza, Ricardo A.; Schulze, Joachim; Salinas Roco, Sebastián; Morales González, Amanda; Amigo, Ramón; Pérez Díaz, Ricardo; Carrasco, Basilio; Contreras Soto, Rodrigo; Maldonado, Carlos; Pedreschi, Romina; Espinoza, Soledad; del Pozo, AlejandroSoil nitrogen (N) acts as an inhibitor to the biological process of N 2 fixation in legumes. Conversely, the phosphorus (P) supply fosters N 2 fixation by promoting nodule formation, facilitating energy transfer, activating enzymes, and enhancing nitrogenase activity. This could help counteract the inhibitory effects that high soil N levels can have on N 2 fixation in legumes. However, there is limited knowledge regarding whether P supply can mitigate the inhibition of N 2 fixation. The objective of this work was to evaluate the effects of two levels of P and five N levels on N 2 fixation, shoot, root, and nodule biomass produced, and metabolic changes of leaves and nodules of Pisum sativum and Vicia faba . N 2 fixation was determined by measuring the natural abundance of 15 N (%Ndfa) in shoots and roots, and metabolites were evaluated using GC -MS. The results showed that increasing N levels led to a reduction of N 2 fixation at the two P levels in both species. However, P supply reduced the inhibitory effect of N addition on N 2 fixation due to higher plant biomass production, which resulted in an increased mass of nodules. Under P deficiency, N addition affected N 2 fixation due to energy production in the nodules, which led to the accumulation of sugars and organic acids, especially in P. sativum . The response of N 2 fixation to a high N supply indicates that P. sativum and V. faba downregulated N 2 fixation but maintained viable nodules to resume the process if the N supply in the soil decreases.
