Abstract
Low phosphorus (P) availability is a major limiting factor facing current agriculture in several agricultural areas. Many P fertilizers are applied to enhance P availability; however, the major part is likely to lose due to various processes related to P cycle. Silicon (Si) treatment and P-solubilizing bacteria inoculation have been emerged as a promising way to improve plant P nutrition. This study aimed to investigate the synergistic effects of Si treatment and Pseudomonas alkylphenolica PF9 strain inoculation on plant growth, P nutrition, acid phosphatase (APase) activity, oxidative stress markers, and antioxidant metabolism in the Moroccan alfalfa population Oued Lmalah (OL) under low P availability. Results revealed a significant reduction in dry biomass, plant height, leaf number, and area under low P conditions. P deficiency also altered P nutrition and chlorophyll (Chl) content. However, P-deficient alfalfa plants treated with Si or inoculated with PF9 strain displayed higher plant growth, Chl content, and remarkably the effect was much higher when Si was applied together with PF9 strain. Moreover, the simultaneous application of Si and PF9 strain to the P-deficient alfalfa plants improved APase activity and as a result, P contents in both the shoots and roots. Results also showed that the application of both the Si and PF9 counteracted the low P availability stress-induced oxidative damage by lowering the accumulation of reactive oxygen species (ROS), electrolyte leakage, and lipid peroxidation. This seems to be related to the ability of both the Si and PF9 strain to modulate both the enzymatic and non-enzymatic antioxidant molecules including superoxide dismutase activity, total polyphenols, flavonoids, and proline contents. Our findings suggest that the combined application of Si and P. alkylphenolica PF9 strain could be a promising way for improving growth of alfalfa under low-P availability.
Highlights
As a perennial forage legume, alfalfa [Medicago sativa L. (M. sativa)] is the most cultivated forage crop in Mediterranean area (Farissi et al, 2011, 2013; Bouizgaren et al, 2013)
We found that Si treatment and P. alkylphenolica PF9 strain inoculation were effective in alleviating low P availability on alfalfa plants and that the application of both the Si and P. alkylphenolica PF9 strain together had a greater effect than their single application
Si treatment or PF9 strain inoculation led to a significant increase (p ≤ 0.001) in total dry weight (TDW) and interestingly the effect was further increased under their combined application
Summary
As a perennial forage legume, alfalfa [Medicago sativa L. (M. sativa)] is the most cultivated forage crop in Mediterranean area (Farissi et al, 2011, 2013; Bouizgaren et al, 2013). Phosphorus is a vital macronutrient required for plant growth and development. It plays important roles in energy transfer, respiration, enzyme activation/inactivation, photosynthesis, and root elongation (Elhaissoufi et al, 2020). The major parts of the applied P are likely to lose due to various biochemical processes related to P cycle including sorption, fixation, and immobilization (Penn and Camberato, 2019). On the another hand, at high concentration, P may cause significant environmental risk from leaching, runoff, and erosion (Bargaz et al, 2021). There is a need for developing strategies that can improve P use efficiency by plants without having any risks on the environment
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