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Due to the rising demand for essential oil in the world market, peppermint has gained an important status among aromatic and medicinal plants. It becomes imperative to optimize its performance in terms of the growth, physiological functioning and biosynthesis of specialized metabolites. A factorial randomized pot experiment was performed using three peppermint cultivars (Kukrail, Pranjal and Tushar) and five levels of leaf-applied nitrogen (N), viz. 0 (control), 0.5, 1.0, 1.5 and 2%. The phenological features, biochemical parameters, viability of root cells, stomatal and trichome behavior were assessed at 100 days after transplanting (DAT). The yield-related parameters, viz., herbage yield, essential oil content, menthol content and yield were studied at 120 DAT. The results revealed that increasing the N doses up to 1.5% enhanced all the studied parameters of peppermint, which thereafter (at the dose above 1.5% N) decreased. The variation pattern of the studied parameters was “low-high-low”. Cultivar Kukrail surpassed the two other cultivars Tushar and Pranjal. Among the foliar sprays, the application of 1.5% N increased chlorophyll content and net photosynthetic rate in all three cultivars. Moreover, the essential oil (EO), EO yield and menthol yield of the plant were also increased linearly in all three cultivars as compared with their control plants. Nitrogen application enhanced the trichome size and density of the plants, as revealed through scanning electron microscopy. Furthermore, from the GC-MS studies, the EO content in the studied cultivars increased, particularly in the case of menthol, with the N application. It may be concluded that two sprays of N (1.5%) at appropriate growth stages could be beneficial for improving morphological, physio biochemical and yield attributes of peppermint.

Plant growth regulators (PGRs) are naturally occurring signaling molecules that modulate numerous phenological traits and physicochemical features of plants throughout their life cycles. Exogenous supplementation of PGRs is an effective strategy for improving the productivity of important agricultural crops. This research was planned to evaluate the effects of six PGRs, namely indole-3-acetic acid (IAA), 24-epibrassinolide (EBL), gibberellic acid (GA3), putrescine (put), salicylic acid (SA) and triacontanol (Tria), on morphology, photosynthesis, nutrient acquisition, and the yield and quality characteristics of three mustard cultivars, i.e., Chutki, Nath Sona, and Rohini. Two foliar sprays each of water, IAA (10−6 M), EBL (10−6 M), GA3 (10−5 M), put (10−3 M), 10−5 M SA, and Tria (10−6 M) were applied to plants at fifty and seventy days after sowing (DAS). The crops’ phenological, physicochemical and microscopic parameters were evaluated at ninety DAS, and yield characteristics were evaluated at harvest (120 DAS). The observations of this study indicated that foliar feeding with PGRs increased all studied parameters, relative to water-spray treatment. The Nath Sona cultivar displayed a stronger response than Rohini and Chutki. Among the leaf-applied PGRs, 24-EBL, followed by IAA and GA3, proved the most effective and improved all the studied parameters. Moreover, the exogenous application of PGRs, especially EBL, significantly enhanced stomatal dimensions and root cell longevity. Treatment with EBL enhanced plant dry weight by 34.7, 35.4, and 37.6%, the net photosynthetic rate by 65.3, 64.7, and 60.2%, seed yield per plant by 67.1, 65.2, and 67.3%, and oil yield per plant by 42.6, 48.2, and 41.1%, in the Chutki, Nath Sona, and Rohini cultivars, respectively, relative to the water-spray treatment. It may be concluded that of the tested PGRs, 24-EBL proved most effective at enhancing the morphological, physicochemical, and yield features of the mustard cultivars.

Background: Due to increasing domestic and industrial demand, edible oil production is not keeping up with demand. To fill this gap, the productivity of oilseeds can be increased by applying adequate nutrients, particularly sulphur (S), at the crucial growth stage. Purpose: The present study aims to explore the best concentration of S for its foliar application on various cultivars of mustard. Methods: A factorial randomized pot experiment was conducted to investigate the role of leaf-applied S on growth, physiobiochemistry, yield and quality traits of three cultivars of Brassica juncea L. (mustard). Five levels of S viz. 0 (water), 15, 30, 45 and 60 ppm S constituted one variant, and the three cultivars (Chutki, Nath Sona and Rohini) were the other variants. The various levels of S were sprayed at 50 and 70 days after sowing (DAS). The growth and physio-biochemical characteristics were studied at 90 DAS, and yield and quality attributes at 120 DAS (harvest). Results: The data indicated that increasing S levels up to 45 ppm S improved all parameters of mustard and thereafter (at the level above 45 ppm S) decreased. Cultivar Nath Sona, followed by Rohini and Chutki, performed best. Among the foliar spray treatment of different levels of S, the application of 45 ppm S increased plant dry weight by 40.21, 35.65 and 30.96%, photosynthetic rate by 28.27, 27.44 and 36.29%, pods of a plant by 15.23, 12.12 and 10.80%, seed yield of a plant by 7.54, 3.89 and 4.91%, oil content by 48.70, 46.31 and 43.15% and oil yield of a plant by 24.56, 23.93 and 22.35% in cultivar Nath Sona, Rohini and Chutki, respectively, compared with their respective water-treated plants. Moreover, the oil was examined by GC-MS technique for its various components. The analysis revealed that there were 36 compounds in the oil of the non-treated plants and 44 compounds in the oil of plants treated with 45 ppm S. The extra compounds resulted from the application of 45 ppm S. Conclusion: It may be concluded that two sprays of 45 ppm S proved effective in improving the growth, physio-biochemical characteristics, yield and quality of cultivars of mustard, particularly Nath Sona.