Chromium is a widespread toxic trace metal in cultivated lands owing to human actions, insufficient treatment, and unregulated disposal. Chromium toxicity is facilitated by the production of reactive oxygen species, which induce lipid peroxidation and damage the cellular membranes and nuclei. This study evaluated the preparation and characterization of Pterospermum-derived biochar based on a set of test categories from the International Biochar Initiative. The aim of this study was to assess the effectiveness of Pterospermum-derived biochar and salicylic acid (SA) in promoting the growth and biochemical attributes of tomato plants grown in Crcontaminated soils. The results showed that Cr toxicity reduced root (42.86 %) and shoot (23.26 %) lengths, which subsequently increased (65 % root and 39.94 % shoot lengths) under SA and biochar treatments. Increased levels of superoxide anions (O2 center dot-) (104.43 %), malondialdehyde (MDA) (115.53 %), and H2O2 (72.35 %) were observed in the Cr-treated tomato plantlets. The combined treatment of SA and biochar effectively reduced MDA, H2O2, and O2 center dot- levels by 51.17%, 36.89%, and 45.53%, respectively, under Cr toxicity conditions. In addition, the combined treatment with SA and biochar enhanced the activity and gene expression of dehydrogenase (7.06fold), guaiacol peroxidase (6.51-fold), superoxide dismutase (7.90-fold), polyphenol oxidase (1.89-fold), glutathione-s-transferase (2.55-fold), ascorbate peroxidase (1.26-fold), and glutathione peroxidase (8.75-fold) under Cr toxicity conditions. The results highlight the combined treatment of biochar and SA as an effective amendment that offers an environment-friendly method for alleviating Cr toxicity and promoting growth and the antioxidative defense system in tomato plantlets.

Silicon, a quasi-essential nutrient element, is well known for imparting tolerance to various biotic and abiotic stresses in crops. The experiments were carried out to evaluate the effect of orthosilicic acid (a silicon source) with two methods of application viz., soil drenching and foliar application against phloem feeders under field conditions for two seasons on two different black gram cultivars. Among the cultivars, Vikral responded better to orthosilicic acid than Pratap Urd 1 regarding the reduction of the population of phloem feeders and enhancement of defense enzyme activity, silicon uptake, total sugars, and total phenols and yield in both the seasons. Among the application methods, soil drenching (2 mLL(-1)) proved to be the superior method of administration to record a significantly low population of phloem feeders, increased activity of defense enzymes, total sugars, and total phenols content, improved activity of coccinellids and yield in both seasons. However, it holds good with the foliar application (2 mLL(-1)) method. Both the application methods were significantly superior to insecticidal check and untreated control treatments. Deposition of silicon was highest in the leaves of black gram (1.541%) when orthosilicic acid was administered through soil than foliar (1.451%) and untreated control (0.891% endogenously available silicon). The highest benefit: cost ratio recorded in soil drenching of orthosilicic acid @ 2 mLL(-1) (1.88 and 1.93) surpassed the B: C ratio of recommended insecticidal check (1.65 and 1.72) during winter and summer seasons, respectively. Both the application methods of orthosilicic acid proved significantly superior over insecticidal check with respect to the management of phloem feeders in black gram including enhanced grain yield, coccinellids activity, and induced biochemical defense as well as the lowest cost of cultivation, which can be easily incorporated with other practices for eco-friendly, sustainable management of phloem feeders in black gram.