Pradipta Kumar Mohapatra

Thiamethoxam is a widely used neonicotinoid known for its effect on soil microbial community. Synechocystis sp. PCC 6803 is a soil cyanobacterium and contributes organic carbon to soil microbial community through active photosynthesis, aiding synergistic soil microbial activity. However, not many studies have been made to decipher the effect of thiamethoxam on the photosynthetic electron transport of soil microalgae and cyanobacteria. We measured the effect of thiamethoxam (0–225 μM) on the growth, physiology, and photochemical performance of Synechocystis sp. PCC 6803 during 24 hr of exposure with an aim to explore its effect on photoelectron transport. Thiamethoxam caused a decrease in the growth and pigment content of Synechocystis, with more of an effect on chlorophyll a and carotenoids than on phycobiliproteins. A concentration-triggered increase in lipid peroxidation and photosynthetic pigment fluorescence was also observed. The OJIP fluorescence transient showed a continuous rise of the O-J phase with thiamethoxam concentration. The performance-indicating parameters φP0 and φE0 decreased, whereas the stress-indicating parameters VJ, M0, and φD0 increased with thiamethoxam treatment. The reaction center functions (Abs/RC, TR0/RC, and ET0/RC) indicated the increase of inactive reaction center with thiamethoxam treatment. The data agree with those obtained by atrazine treatment and indicated that the insecticide imposed a Photosystem II (PS II) herbicide–like effect on the acceptor side of PS II of Synechocystis. The inhibition of PS I reduction and decreased PS I functions support our conclusion. Our observation will enable researchers to evaluate the on-site effects of thiamethoxam on crop plants.

Antibiotics are extensively used to manage human, animal and plant ailments caused by microbial infections. However, rampant use of antibiotics has led to the development of antibiotic resistance, which is a public health concern. The development of antibiotic resistance is significantly influenced by agro-ecosystems. Rice agroecosystem receives high levels of antibiotics from direct applications, and sources like manure and irrigation water. Consequently, uptake of antibiotic residues by rice (Oryza sativa L.) is resulting in accumulation of antibiotics in plant parts. Accumulation of these antibiotics can be toxic to plant, and can be partitioned to rice grain and straw, and reach the human and animal food chain leading to the development of antibiotic resistance. Moreover, the antibiotics can alter soil microbes, which would result in loss of production. This study compiles information from existing literature on global antibiotic usage and explores how antibiotics enter the rice ecosystem through contaminated wastewater, manure, sewage sludge, and through direct application. A detailed discussion on the persistence and movement of antibiotics in different environment compartments is provided. The review also highlights the impacts of antibiotics on plants and natural microbiota, as well as issues pertaining to antimicrobial resistance in public health sectors. For sustainable mitigation of the issues of antibiotic residues in rice ecosystem, we suggest application of decontaminated manure, microbial bioremediation, optimization of the use of plant-based alternatives, enhancing regulations, and fostering global collaboration. We advocate integrated disease management approaches which can significantly reduce the antibiotic use in rice agroecosystem.

Leaf ontogeny of tropical evergreen tree species lasts several months with changes in size, shape, colouration and internal tissue distribution of leaves. Leaf initiation in Saraca asoca generally occurs once in a year during February–April, followed by very limited leafing thereafter. We measured the rate of photosynthesis, chlorophyll a fluorescence, energy quenching and PSII functions during the leaf ontogeny process. Observations were taken up to 35 days after opening of lamina (DAOL). Significant increase in the synthesis and accumulation of photosynthetic pigments but negative net photosynthesis was noticed during initial days of the ontogeny. The leaf moved from heterotrophy to autotrophy with gradual improvement of PSII functions. The ratio of intercellular CO2 (Ci) and ambient CO2 (Ca) showed significant change at ≥11 DAOL. Increase in the age of the leaf (between 5 and 28 DAOL) caused decrease in O-J rise and corresponding increase in J-I and I-P rise as well as of fluorescence maximum (FM) of the OJIP curve. The improvement of the electron transport components of the donor side of PSII was seen with increase in the functional oxygen evolving complex. The functional improvements of the donor and acceptor side of PSII during leaf ontogeny are discussed.

Mangroves are abundant in bioactive natural substances that fight off pathogenic diseases. Different parts of R. apiculata, an abundant mangrove found in Bhitarkanika National Park, India were extracted with methanol and a mixture of solvents methanol/ethanol/chloroform (60 : 20 : 20) to evaluate their antimicrobial properties. The combination solvent extract of bark had the highest zone of inhibition (ZOI) of 18.62 mm against Pseudomonas aeruginosa and a ZOI of 17.41 mm against Streptococcus mitis. Bark extracts had the highest DPPH (43 %) and FRAP (96 %) activities. The combination solvent bark extract of R. apiculata had the highest ZOI of 20.42 mm (lowest MIC of 2.12 μg/ml) against Candida albicans and ZOI of 15.33 mm (MIC of 3.02 μg/mL) against Penicillium chrysogenum. Combination bark extracts of R. apiculata contained flavanols than methanolic extracts. The crude extract of R. apiculata bark made with a mixture of solvents containing more active ingredients could be used in novel drug formulation.

Mohanty A, Acharya S, Swain BB, Mishra S, Mohapatra D, Mohapatra PK. 2023. Integrated nutrient management enhances the growth efficiency and productivity of Tagetes erecta cv. Sirakole. Asian J Agric 7: 88-97. The African marigold (Tagetes erecta L. cv. Sirakole) is a highly significant plant because it can be cultivated year-round, produce large blooms, have a long post-harvest life, and compactness. To determine the optimal fertilizer and manure combination, we conducted a study to explore the plant's morphological, yield, and physiological characteristics under different combinations of fertilizers, Vermicompost (VC), Poultry Manure (PM), and biofertilizer (Azospirillium + phosphate solubilizing bacteria). The most successful combination for promoting vigorous growth, dense canopy, prolific branching, longer flowering duration, large-sized flowers, and higher yield was achieved with 50% Recommended Dose of Nitrogen and Phosphorus (RDNP) + VC equivalent to 25% Recommended Dose of Nitrogen (RDN) + PM equivalent to 25% RDN + biofertilizers (@400 gha^-1). Additionally, plants in this combination exhibited higher chlorophyll content (Chl) and photosynthesis (P_N) than those in plots with RDNP alone or other amendments. While photosynthetic fluorescence yield jP₀) and energy dissipation (jD₀) did not vary, plots with RDNP had lower excitation (?₀) and electron movement (jE₀), as well as lower photosynthesis performance indices (PIs), compared to the nutrient combinations. Additionally, the organically amended plots showed higher microbial density and soil enzyme activities than those with RDNP alone. Our findings indicate that using a combination of fertilizer, manure, and biofertilizers is the most effective way to improve the photosynthetic capacity and flower yield of T. erecta cv. Sirakole.