Comprehensive analysis of silicon impact on defense and metabolic responses in rice exposed to herbivory stress.

Silicon (Si) uptake is generally beneficial for plants that need protection from insect herbivores. In pursue of mechanisms involved in Si-mediated defense, we comprehensively explored the impact of Si on several defensive and metabolic traits in rice exposed to simulated and real herbivory of Mythimna loreyi Duponchel larvae. Hydroponic experiments showed that Si-deprived rice supplemented with Si 72 h prior to insect infestation were similarly resistant to larvae as plants continuously grown in Si-containing media. Both Si and herbivory altered primary metabolism in rice, including the levels of several sugars, amino acids, and organic acids. While the accumulation of sugars was generally positively correlated with Si presence, multiple amino acids showed a negative correlation trend with Si supplementation. The levels of secondary metabolites, including isopentylamine, p-coumaroylputrescine and feruloylputrescine, were typically higher in the leaves of Si-supplemented plants exposed to herbivory stress compared to Si-deprived plants. In addition, simulated herbivory treatment in Si-supplemented plants induced more volatile emissions relative to Si-deprived plants, which was consistent with the increased transcripts of key genes involved in volatile biosynthesis. In ecological interactions, Si alone did not affect the oviposition choice of M. loreyi but gravid females showed a significant preference for simulated herbivory-treated/Si-deprived compared to Si-supplemented plants. Our data suggest that apart from mechanical defense, Si may affect rice metabolism in multiple ways that might enhance/modulate defense responses of rice under herbivory stress.

Use of Catharanthus roseus Cell Cultures for the Synthesis of Metal Nanoparticles.

Metal nanoparticles have found applications in many fields owing to their unique physicochemical characteristics and ease of surface functionalization. Crucial for these applications is the development of environmentally friendly strategies for nanoparticle preparation. Nanoparticles can be prepared using several physical and chemical methods; however, the use of nontoxic and eco-friendly approaches is receiving increasing attention. Plant cell cultures are sustainable sources of bioactive compounds that can act as reducing and stabilizing agents during nanoparticle synthesis. Here, we describe the procedures used to synthesize silver and gold nanoparticles with cultured cells of Catharanthus roseus. The bioreduction of silver ions to nanoparticles with extract of seed-derived callus of C. roseus is evident from UV-Vis spectroscopy results wherein an absorption maxima is observed at 425 nm, indicating the formation of elemental silver. Similarly, reaction mixtures containing cell-free suspension culture filtrate of C. roseus and gold III ions turn wine red after 24 h incubation because of gold nanoparticle formation. These methods can be easily adapted for use in the preparation of other metal nanoparticles.

Stable antibacterial silver nanoparticles produced with seed-derived callus extract of Catharanthus roseus.

Biocompatibility and ecotoxicity concerns associated with chemically produced metallic nanoparticles have led to an increasing interest in the development of environmentally benign alternatives for nanoparticle synthesis using biological platforms. Herein, we report the utilization of an extract of seed-derived callus of Catharanthus roseus for the production of stable silver nanoparticles (Ag NPs). The bioreduction of silver ions was evident from UV-Vis spectroscopy results: the absorption maxima were observed at 425 nm, indicative of elemental silver. Transmission electron micrographs revealed that the Ag NPs were well-dispersed and predominantly spherical with particle sizes in the range of 2-15 nm. The synthesized Ag NPs exhibited colloidal stability in an aqueous dispersion for a period of 120 days, as indicated by UV-Vis absorbance spectra and zeta potential measurements. Fourier transform infrared spectroscopy revealed the possible utilization of hydroxyl groups and amides in the reduction of silver ions and surface stabilization of the Ag NPs, respectively. Notably, the synthesized Ag NPs showed considerable antibacterial action against Escherichia coli even after 8 weeks of storage under ambient conditions. Thus, cell extracts of cultured callus of Catharanthus roseus could be explored as an ecofriendly platform for the synthesis of stable and functional nanoparticles.

Assessment of Palm Press Fibre and Sawdust-Based Substrate Formulas for Efficient Carpophore Production of Lentinus squarrosulus (Mont.) Singer.

Development of efficient substrate formulas to improve yield and shorten production time is one of the prerequisites for commercial cultivation of edible mushrooms. In this study, fifteen substrate formulas consisting of varying ratios of palm press fibre (PPF), mahogany sawdust (MS), Gmelina sawdust, wheat bran (WB), and fixed proportions of 1% calcium carbonate (CaCO3) and 1% sucrose were assessed for efficient Lentinus squarrosulus production. Proximate compositions of mushrooms produced on the different substrate formulas were also analysed and compared. Substrate formulations containing 85% PPF, 13% WB, 1% CaCO3, and 1% sucrose were found to produce the highest carpophore yield, biological efficiency and size (206.5 g/kg, 61.96%, and 7.26 g, respectively). Days to production (first harvest) tended to increase with an increase in the amount of WB in the substrate formulas, except for PPF based formulas. The addition of WB in amounts equivalent to 8~18% in substrate formulas containing 80~90% PPF resulted in a decrease in the time to first harvest by an average of 17.7 days compared to 80~90% MS with similar treatment. Nutritional content of mushrooms was affected by the different substrate formulas. Protein content was high for mushrooms produced on formulas containing PPF as the basal substrate. Thus, formulas comprising PPF, WB, CaCO3, and sucrose at 85% : 13% : 1% : 1%) respectively could be explored as starter basal ingredients for efficient large scale production of L. squarrosulus.