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Under intensive agriculture, weeds cause heavy losses in crop yield and quality. The existing manual method of weed control is no longer sustainable because of paucity of labours, higher wage, and huge drudgery. Herbicide is an easier, more efficacious, and economical tool for weed control in crops and un-cropped situations. However, the consequences of herbicide use, concerning non-target toxicities, and the evolution of herbicide-resistant weeds have drawn the attention of world communities. Therefore, in this review, we attempt to highlight the potential benefits vis-à-vis harmful consequences of herbicides in diversified crop ecologies across the world. Herbicide use resulted in weed control efficiency of 52–96% in different agro-ecologies. Besides, it could increase grain yield of different arable crops by 19–372% with an additional economic benefit of US$ 305 - US$ 867 over unweeded control. Chemical weed management resulted in gain in net returns by 4–12% over manual weeding (∼two hand weedings) and by 7–247% over the weed-free check in different countries. The majority of herbicides used at recommended doses in crops did not show any direct and/or residual toxicity on soil micro-organisms in agro-ecologies. Environmental conditions may change pesticide impacts on non-target micro-organisms. Over-reliance on herbicides and injudicious use at higher rates may lead to a fragile ecosystem, but judicious use can stimulate productivity, profitability and livelihood security. Hence, integrated weed management (IWM) that can restrict weed populations below threshold level, reduce environmental foot-print, increase cropping system sustainability, and reduce selection pressure for weed resistance to herbicides has been suggested. • Chemical weed management increased 4–12% returns and 52–96% efficacy over manual weeding. • Herbicides at recommended doses did not show any toxicity on soil micro-organisms. • Environmental conditions change impacts of herbicides on non-target microorganisms. • Over-reliance on herbicides and injudicious use may lead to a fragile ecosystem. • Integration of herbicides with suitable methods is recommended for environmental safety. [ABSTRACT FROM AUTHOR]

Extraction of eugenol from dried tulsi leaves powder ( Ocimum sanctum Linn.) of ‘West Bengal origin’ (Eastern India), Ram tulsi variety, was carried out using supercritical carbon dioxide (SC-CO 2 ) extraction. The optimized parameters for highest yield of eugenol [2.96 mg (g dry tulsi leaves) −1 ] were 20 g of tulsi leaves powder (d p = 0.42 mm) extracted at 50 °C, 200 bar and 90 min extraction time at a constant flow rate of 2.5 L min −1 of gaseous CO 2 . Statistical analyses revealed that only extraction pressure showed significantly effect on the yield of eugenol. The extraction kinetics of eugenol from tulsi matrix followed first order kinetics (Higuchi model). Characterization of the packed bed of tulsi leaves was also carried out during steady and unsteady states of extraction and empirical correlations were developed among dimensionless Reynolds, Sherwood and Schmidt numbers. The correlation coefficients were found to be low owing to leaf mucilage which impeded extraction of eugenol from tulsi leaves. [ABSTRACT FROM AUTHOR]

Volatile organic compounds emitted by plants (pVOCs) protect themselves from abiotic and biotic stresses. Plants are under constant threats from biotic stress especially herbivores which facilitate plants to emit herbivore-induced plant volatiles (HIPVs), an inducible defense in plants against herbivores by communicating to herbivores' natural enemies and neighboring plants. HIPVs are reported to act as feeding and/or oviposition deterrents to herbivores, belonging to four major groups including terpene/terpenoids, benzenoids and phenylpropanoids, the volatile fatty acid derivatives, and the volatile aminoacid derivatives. However, the plant volatile profiles induced by herbivores have been reported to be altered by silicon (Si)-fertilization, priming of plants with chemical elicitors and climate change which can induce plants to produce and emit novel plant volatiles that are not expressed by plants in response to damage by herbivory. Transgenic crops and/or sentinel crops with enhanced pVOCs emission profiles have been proposed to improve plant resistance, health and yields. Currently several technological advances in devices including field-portable electronic devices (e-Nose) and hand-held smartphone-based biosensors for in situ early detection of pVOCs profiles which are now available and supported by artificial intelligence (AI), to increase detection accuracy of these systems. The present review highlights the multi-dimension approaches emerging in pVOCs research for early and rapid detection of specific VOCs indicators as markers with associated plant biotic stressors. [Display omitted] • Biotic and abiotic factors induce plants to emit volatile organic compounds (pVOCs), belonging to four major groups. • Herbivore induced plant volatiles (HIPVs) rescue plants from their herbivores by attracting herbivores' natural enemies. • Allelopathy effects of pVOCs smother non-economical crops. • Exogenous application of Silicon, chemical elicitors and climate change significantly modify the HIPV profiles. • Companion/transgenic crops can be employed to enhance pVOCs emissions for IPM. • pVOCs repository can be raw material for development of plant phenotyping tools including e-Nose, biosensors etc. [ABSTRACT FROM AUTHOR]