Application of green synthesized bimetallic nZVI-Cu nanoparticle as a sustainable alternative to chemical fertilizers to enhance growth and photosynthetic efficiency of rice seedlings.

Application of nanomaterials in agriculture has been extensively explored over the past decade leading to a wide ambit of nanoparticle-based agrochemicals. Metallic nanoparticles consisting of plant macro- and micro-nutrients have been used as nutritional supplements for plants through soil amendments, foliar sprays, or seed treatment. However, most of these studies emphasize monometallic nanoparticles which limit the range of usage and effectivity of such nanoparticles (NPs). Hence, we have employed a bimetallic nanoparticle (BNP) consisting of two different micro-nutrients (Cu & Fe) in rice plants to test its efficacy in terms of growth and photosynthesis. Several experiments were designed to assess growth (root-shoot length, relative water content) and photosynthetic parameters (pigment content, relative expression of rbcS, rbcL & ChlGetc.). To determine whether the treatment induced any oxidative stress or structural anomalies within the plant cells, histochemical staining, anti-oxidant enzyme activities, FTIR, and SEM micrographs were undertaken. Results indicated that foliar application of 5 mg L-1 BNP increased vigor and photosynthetic efficiency whereas 10 mg L-1 concentration induced oxidative stress to some extent. Furthermore, the BNP treatment did not perturb the structural integrity of the exposed plant parts and also did not induce any cytotoxicity. Application of BNPs in agriculture has not been explored extensively to date and this study is one of the first reports that not only documents the effectivity of Cu-Fe BNP but also critically explores the safety of its usage on rice plants making it a useful lead to design new BNPs and explore their efficacy.

Fe3O4-urea nanocomposites as a novel nitrogen fertilizer for improving nutrient utilization efficiency and reducing environmental pollution.

Almost 81% of nitrogen fertilizers are applied in form of urea but most of it is lost due to volatilization and leaching leading to environmental pollution. In this regard, slow-release nano fertilizers can be an effective solution. Here, we have synthesized different Fe3O4-urea nanocomposites with Fe3O4 NPs: urea ratio (1:1, 1:2, 1:3) ie. NC-1, 2, and 3 respectively, and checked their efficacy for growth and yield enhancement. Oryza sativa L. cv. Swarna seedlings were treated with different NCs for 14 days in hydroponic conditions and significant up-regulation of photosynthetic efficiency and nitrogen metabolism were observed due to increased availability of nitrogen and iron. The discriminant functional analysis confirmed that the NC3 treatment yielded the best results so further gene expression studies were performed for NC-3 treated seedlings. Significant changes in expression profiles of ammonia and nitrate transporters indicated that NC-3 treatment enhanced nitrogen utilization efficiency (NUE) due to sustained slow release of urea. From pot experiments, we found significant enhancement of growth, grain nutrient content, and NUE in NC supplemented sets. 1.45 fold increase in crop yield was achieved when 50% N was supplemented in form of NC-3 and the rest in form of ammonium nitrate. NC supplementation can also play a vital role in minimizing the use of bulk N fertilizers because, when 75% of the recommended N dose was supplied in form of NC-3, 1.18 fold yield enhancement was found. Thus our results highlight that, slow-release NC-3 can play a major role in increasing the NUE of rice.