Biostimulants are the next-generation choice for sustainable agricultural production and are gradually becoming an alternative to synthetic chemicals. Various botanicals are proposed to exert stimulatory effects, and garlic allelochemicals are among such botanicals; however, a peer-reviewed scientific evaluation is required to understand garlic-derived substances such as biostimulants. Current studies were therefore performed to identify the bioactivity of garlic extract as a biostimulant to improve crop quality, alter its physiological potential, and prime its defense responses against pathogenic fungal infections. 100 µg mL⁻¹ aqueous garlic extracts (AGE) in consort with 1 mM of acetyl salicylic acid (ASA) and distilled water as a control treatment were applied to eggplant and pepper seedlings as foliar application and fertigation methods. The results revealed stimulatory responses in the growth of the vegetables with improved plant height, number of leaves, root growth, fresh and dry weight, etc., due to AGE and ASA applications. Moreover, significant alterations were indicated in plant metabolites such as chlorophyll, carotenoids, and soluble sugars. Additionally, stimulation of the antioxidant enzymes such as superoxide dismutase (SOD) and peroxidase (POD), as well as the root activity of these plants, was observed after treatment. Application of AGE and ASA also exerted priming effects on pepper plants, inducing defense responses prior to Phytopthora capsici inoculation, and the treated plants therefore successfully resisted infection through activated antioxidant systems, and probably carotenoid and other protectory metabolites. Stress-induced H₂O₂ content was extremely low in the treated plants, indicating successful resistance against pathogenic infection.

Growth and bulb development in garlic is affected considerably by variations in photoperiod and temperature thereby influencing its morphology, physiology, and nutritive quality. Varied combinations of photoperiods and temperatures may influence the bulb development and quality, and can determine the suitability of a cultivar for a particular region. Experiments were conducted to study the impact of different photoperiod and temperature combinations on the growth, morpho-physiology, and nutritive quality of garlic bulb. Three garlic cultivars viz; G103, G024, and G2011-5 were exposed to different combinations of photoperiod (8 h/16 h, 10 h/14 h, 12 h/12 h, 14 h/10 h, 16 h/8 h (light/dark)) and temperature (20 °C/15 °C, 25 °C/18 °C, and 30 °C/20 °C). Results revealed that longer photoperiod (14 h or 16 h) and higher temperature (25 °C or 30 °C) treatments significantly improved the garlic bulbing imparting maximum bulb diameter, height, bulbing index, and the shortest growth period. Whereas, 12-h photoperiod had maximum bulb weight. In addition, total soluble solid (TSS), content of soluble protein, soluble sugar, total sugar, glucose, sucrose, fructose, starch, total phenols, and total flavonoids increased significantly because of 14-h photoperiod and 30 °C temperature condition, however exhibited decline with 8 h photoperiod and lowest temperature (20 °C). These alterations were related to bulb characteristics and bulbing index. Maximum plant standing height and pseudostem diameter of the garlic plant were observed at 20 °C. Additionally, plants under the combination of 14 h–30 °C had maximum fresh weight, bulb diameter, shortest growth period, maximum physiological and nutritive quality traits of the bulb, while as 12 h–30 °C combinations resulted in maximum bulb weight and 16 h–30 °C had maximum bulb height. Among cultivars cv. G103 showed best response to tested photoperiod and temperature combinations in terms of morpho-physiological and biochemical attributes studied, except for bulbing index which was maximum in cv. G024. Present study concludes the influence of photoperiod and temperature combinations on garlic growth and bulbing characteristics through the modulations induced in soluble protein, sugars, and phenolic compounds.

The current study was aimed to evaluate the seed priming potential of AGE (aqueous garlic extracts) to enhance seed germination and early seedling growth of eggplant. Different concentrations (100, 200, and 300 µg mL⁻¹) of AGE were evaluated along with methyl jasmonate (MeJA) and salicylic acid (SA), plant growth regulators with reported seed priming potential whereas, water was taken as a control treatment. Eggplant seeds were primed for 4-, 8-, and 12-h and seed germination traits such germination rate index, germination percentage, mean germination time, and early seedling growth traits such as fresh and dry weights, root, and shoot lengths were observed. Moreover, plant antioxidant enzymes activities and lipid peroxidation levels, soluble protein contents and reactive oxygen species were monitored to establish the stimulatory/inhibitory effects of the treatments. Our results indicate priming potential of AGE, SA, and MeJA to enhance seed germination and early seedling growth in eggplant and the effects were obvious in various morphological and physiological traits. Seed priming significantly altered the antioxidant enzymes activities such as superoxide dismutase (SOD), and peroxidase (POD) with alteration in the reactive oxygen species (ROS). Interestingly, priming duration also affected the bioactivity of these chemicals because seed priming with 300 µg mL⁻¹ AGE for 4 h had a positive influence, however, prolonged exposure to the same concentration inhibited the seed germination process and induced oxidative stress on the seedlings with elevated levels of malondialdehyde (MDA) content. We propose AGE seed priming as a bio-stimulant to enhance seed germination and early seedling growth in eggplant, and the results hence lay the foundation for the preparation of garlic-based compounds to improve vegetables production under plastic tunnels and greenhouse production units.