Silicon nanoparticles: Comprehensive review on biogenic synthesis and applications in agriculture.

Recent advancements in nanotechnology have opened new advances in agriculture. Among other nanoparticles, silicon nanoparticles (SiNPs), due to their unique physiological characteristics and structural properties, offer a significant advantage as nanofertilizers, nanopesticides, nanozeolite and targeted delivery systems in agriculture. Silicon nanoparticles are well known to improve plant growth under normal and stressful environments. Nanosilicon has been reported to enhance plant stress tolerance against various environmental stress and is considered a non-toxic and proficient alternative to control plant diseases. However, a few studies depicted the phytotoxic effects of SiNPs on specific plants. Therefore, there is a need for comprehensive research, mainly on the interaction mechanism between NPs and host plants to unravel the hidden facts about silicon nanoparticles in agriculture. The present review illustrates the potential role of silicon nanoparticles in improving plant resistance to combat different environmental (abiotic and biotic) stresses and the underlying mechanisms involved. Furthermore, our review focuses on providing the overview of various methods exploited in the biogenic synthesis of silicon nanoparticles. However, certain limitations exist in synthesizing the well-characterized SiNPs on a laboratory scale. To bridge this gap, in the last section of the review, we discussed the possible use of the machine learning approach in future as an effective, less labour-intensive and time-consuming method for silicon nanoparticle synthesis. The existing research gaps from our perspective and future research directions for utilizing SiNPs in sustainable agriculture development have also been highlighted.

Hydrogen sulfide manages hexavalent chromium toxicity in wheat and rice seedlings: The role of sulfur assimilation and ascorbate-glutathione cycle.

The role of hydrogen sulfide (H2S) is well known in the regulation of abiotic stress such as toxic heavy metal. However, mechanism(s) lying behind this amelioration are still poorly known. Consequently, the present study was focused on the regulation/mitigation of hexavalent chromium (Cr(VI) toxicity by the application of H2S in wheat and rice seedlings. Cr(VI) induced accumulation of reactive oxygen species and caused protein oxidation which negatively affect the plant growth in both the cereal crops. We noticed that Cr(VI) toxicity reduced length of wheat and rice seedlings by 21% and 19%, respectively. These reductions in length of both the cereal crops were positively related with the down-regulation in the ascorbate-glutathione cycle, and were recovered by the application NaHS (a donor of H2S). Though exposure of Cr(VI) slightly stimulated sulfur assimilation but addition of H2S further caused enhancement in sulfur assimilation, suggesting its role in the H2S-mediated Cr(VI) stress tolerance in studied cereal crops. Overall, the results revealed that H2S renders Cr(VI) stress tolerance in wheat and rice seedlings by stimulating sulfur assimilation and ascorbate-glutathione which collectively reduce protein oxidation and thus, improved growth was observed.

Ethylene needs endogenous hydrogen sulfide for alleviating hexavalent chromium stress in Vigna mungo L. and Vigna radiata L.

Chromium toxicity to crops is a big scientific issue of the present time. Thus, continuous scientific attempts have been taken for reducing chromium toxicity in crop plants. In this study, we have tested potential of ethylene (ET) and hydrogen sulfide (H2S) in alleviating hexavalent chromium [(Cr(VI)] stress in two pulse crops i.e. black bean and mung bean. Cr(VI) declined growth (by 21 % and 27 % in black and mung bean, respectively) and also negatively affected photosynthesis in both pulse crops due to accumulation of Cr(VI) and cell death in roots. Under similar conditions, levels of reactive oxygen species (ROS) were enhanced but antioxidant defense system showed differential responses. The addition of AVG (an inhibitor of ethylene biosynthesis) and PAG (an inhibitor of H2S biosynthesis) with Cr(VI) further increased toxicity of Cr(VI) suggesting that endogenous H2S and ET are important for tolerating Cr(VI) toxicity. But supplementation of either ET or H2S alleviated Cr(VI) toxicity. Interestingly, ET did not rescue negative effects of PAG under Cr(VI) stress but NaHS rescued negative effect of AVG. Overall, results indicate that though both ET and H2S are able in alleviating Cr(VI) stress but endogenous H2S is crucial in ET-mediated mitigation of Cr(VI) stress. Furthermore, H2S appears to be a downstream signal of ET in alleviating Cr(VI) stress in two pulse crops.

A brief appraisal of ethylene signaling under abiotic stress in plants.

For years, ethylene has been known to humankind as the plant hormone responsible for fruit ripening. However, the multitasking aspect of ethylene is still being investigated as ever. It is one of the most diversified signaling molecules which acclimatize plant under adverse conditions. It promotes adventitious root formation, stem and petiole elongation, opening and closing of stomatal aperture, reduces salinity and metal stress, etc. Presence of ethylene checks the production and scavenging of reactive oxygen species by strengthening the antioxidant machinery. Meanwhile, it interacts with other signaling molecules and initiates a cascade of adaptive responses. In the present mini review, the biosynthesis and sources of ethylene production, interaction with other signaling molecules, and its exogenous application under different abiotic stresses have been discussed.

Prospective evaluation of XRCC-1 Arg194Trp polymorphism as bio-predictor for clinical outcome in locally advanced laryngeal cancer undergoing cisplatin-based chemoradiation.

BACKGROUND: To determine X-ray repair cross-complementing 1 gene (XRCC-1) Arg194Trp polymorphism as bio-predictor for clinical outcome in advanced laryngeal squamous cell carcinoma undergoing cisplatin-based chemoradiation (CRT). METHODS: A total of 150 patients were enrolled in this prospective study. XRCC-1 Arg194Trp genotyping categorized patients as wild (C/C) and polymorphic (C/T or T/T). The primary endpoint was to assess acute radiation-induced toxicity (ARIT). RESULTS: A significant correlation of skin (P- .04) and oral mucosal ARIT (P- .01) was noticed in the XRCC-1 polymorphic variant. A higher treatment response was noted in the polymorphic variant, and it shows a trend toward significance (P- .08). With 33 months of median follow-up, 2-year progression-free survival (PFS) and overall survival (OS) of wild vs polymorphic variant were 34.6% vs 46.9% (P- .066) and 50.6% vs 62.2% (P- .12). CONCLUSION: XRCC-1 polymorphic variants have significantly higher grade of >2 ARIT and may have improved trend for treatment response and PFS.