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.

Foliar application of selenium affecting pollen viability, grain chalkiness, and transporter genes in cadmium accumulating rice cultivar: A pot study

Under Cadmium (Cd) stress, rice grain quality and quantity are compromised, affecting human health. Application of Selenium (Se) mitigating Cd stress in rice was already reported, but its role in rescuing Cd induced damage in the reproductive parts in rice plants has not been studied before. To investigate the underlying mechanism, Se mediated alleviation of Cd-stress induced damage to pollen viability, germination rate, and grain chalkiness were studied. A grain Cd accumulating rice genotype was selected and treated with 10 μM Cd and sprayed with 5 μM Se during tillering, elongating and heading stages. A significant reduction in pollen viability, germination percentage, and accumulation of higher amount of ROS in the reproductive parts were observed in Cd treated plants. However, Se supplementation (i.e. Cd + Se), decreased the ROS accumulation in anther, pistil, pollen and enhanced the pollen viability and germination percentage. Cd translocation was prevented from flag leaf to grains, under Se treatment. As a result, a significantly higher seed setting rate, and yield were observed. Additionally, Se improved grain nutrient content and grain quality. Therefore, the recent study suggests that the use of foliar spray of Se could be a cost-effective strategy to prevent Cd-induced yield loss and quality in rice.

Surface functionalization and size of polystyrene microplastics concomitantly regulate growth, photosynthesis and anti-oxidant status of Cicer arietinum L

Microplastics are a recent entrant in the list of environmental pollutants, exhibiting great diversity owing to different sizes, surface charges, and morphologies. The present study explores the impact of varied size, surface functionalization, and concentration of polystyrene microplastics (PS MP) on plants. For this study, Cicer seedlings were exposed to two different sizes of PS (1 μm and 12 μm) with three different surface functionalization (plain, carboxylated, and aminated) and at three distinct concentrations (10, 50, and 100 mg/L). The growth and photosynthetic parameters (like pigment content, Hill activity, etc.) along with oxidative stress marker (ROS) and anti-oxidant enzyme activities (like Superoxide dismutase, Catalase, and Peroxidase) were assessed. The results incline towards the idea that with increasing concentration of PS, there was a decline in the growth of the seedlings. There was also a dose-dependent increase in oxidative stress due to the suppression of the action of antioxidant enzymes. The effect was more prominent for 12 μm PS, perhaps due to its larger size and adherence to roots resulting in mechanical damage as deduced from MDA levels in the seedlings. Besides, MP with negative surface charge was comparatively less toxic than uncharged or positively charged PS of 1 μm. Overall, it can be concluded that the impact of MP on plants does not rely on individual characteristics of the particles alone, rather it is a concerted result of various determinants like size, charge, and concentration.

Genotypic variation among 20 rice cultivars/landraces in response to cadmium stress grown locally in West Bengal, India

Cadmium (Cd) is a hazardous soil contaminant and causes environmental toxicity when present beyond the allowable limit in soil. It can alter growth and metabolism in both plants and animals even at very low concentration. Being sessile in nature, plants try to evade this harmful effect by adopting various defence mechanisms including activation of antioxidants and other metal homeostasis mechanisms. This study shows the varietal Cd stress tolerance capacity of rice cultivars commonly grown in West Bengal, which is a rice biodiversity region in India. Seven days old rice (Oryza sativa L.) seedlings were treated with 10 μM CdCl₂ for another 7days and different physiological and biochemical stress parameters were studied to compare the varietal stress responses. Principle component analysis (PCA) and root tolerance index (RTI) revealed that rice cultivars I.E.T-4786, Jamini and Netiya, Maharaj showed divergent stress responses towards susceptibility and tolerance. Histochemical localization of hydrogen peroxide (H₂O₂), superoxide (O₂˙^-) and pot experiment were performed in these four cultivars (I.E.T-4786-Jamini and Netiya-Maharaj) to elucidate the different Cd stress tolerance. Histochemical analysis, agronomic traits and grain Cd content analyses showed that I.E.T-4786 and Jamini were susceptible with no Cd accumulation in grain, whereas cultivars Netiya and Maharaj were stress tolerant and Cd accumulators. In addition, health risk assessment was monitored for dietary intake of Cd through Cd accumulating rice and non Cd accumulating rice genotypes were identified. Thus, the study identified the Cd tolerant and sensitive cultivars grown locally.