Gibberellins (GAs) are important phytohormones that regulate many developmental processes in plants. Clove, as the reproductive organ of garlic, dramatically affected garlic bulb development. Considering the potential of gibberellins in plant development and our previous studies, we investigated the effect of soaking two types of seed cloves (seed clove-I: without root/shoot sprouting; seed clove-II: with root/shoot sprouting) in GA₃ solution on axillary bud development and examined the effect of soaking seed cloves in GA₃ solution on bulb development, phytohormone level and sugar content in this study. Results indicated seed clove types, soaking liquids and their interaction significantly affected the number of cloves per bulb and the rate of single-clove bulb. Moreover, soaking seed cloves in 1 mmol L⁻¹ GA₃ solution for 24 h not only promoted axillary bud formation and secondary plant growth (equal to tillering or branching), but also slightly increased the number of cloves per bulb and changed bulb structure with a low yield and marketable quality. On the 40th day after GA₃ treatment (at axillary bud outgrowth stage), zeatin riboside (ZR) and soluble protein in stem were sharply increased with the increase of GA₃, sucrose, fructose and soluble protein in leaf. However, GA₃, indole-3-acetic acid (IAA), soluble sugar and sucrose in stem (3.52 ng g⁻¹ fresh weight (FW), 19.88 ng g⁻¹ FW, 237.3 mg g⁻¹ FW, and 8.24 mg g⁻¹ FW, respectively) were significantly decreased on the 40th day after GA₃ treatment, compared to the control of water treatment (5.56 ng g⁻¹ FW, 32.96 ng g⁻¹ FW, 263.6 mg g⁻¹ FW, and 10.37 mg g⁻¹ FW, respectively). To our knowledge, these novel results indicate seed cloves soaked in GA₃ solution promotes axillary bud formation and outgrowth that caused the changes in plant architecture and bulb structure. Meanwhile, our findings suggest that the level of endogenous plant hormone (GA₃, IAA and ZR) cooperates with the content of sugar (sucrose and fructose) in leaf and stem to regulate axillary bud outgrowth in garlic.

The number of cloves in a garlic bulb is controlled by axillary meristem differentiation, which directly determines the propagation efficiency. Our previous study showed that injecting garlic plants with gibberellins (GA₃) solution significantly increased clove number per bulb. However, the physiological and molecular mechanism of GA-induced axillary bud formation is still unknown. Herein, dynamic changes in histology, phytohormones, sugars and related genes expression at 2, 4, 8, 16 and 32 days after treatment (DAT) were investigated. Histological results indicated two stages (axillary meristem initiation and dormancy) were in the period of 0–30 days after GA₃ treatment. Application of GA₃ caused a significant increase of GA₃ and GA₄, and the downregulation of AsGA20ox expression. Furthermore, the change trends in zeatin riboside (ZR) and soluble sugar were the same, in which a high level of ZR at 2 DAT and high content of soluble sugar, glucose and fructose at 4 DAT were recorded, and a low level of ZR and soluble sugar arose at 16 and 32 DAT. Overall, injection of GA₃ firstly caused the downregulation of AsGA20ox, a significant increase in the level of ZR and abscisic acid (ABA), and the upregulation of AsCYP735 and AsAHK to activate axillary meristem initiation. Low level of ZR and soluble sugar and a high level of sucrose maintained axillary meristem dormancy.

Garlic has a strong ability of selenium (Se) accumulation and is one of the best target crops for Se biofortification. Arbuscular mycorrhizal fungi (AMF) inoculation might enhance the nutritional qualities and the absorption ability of exogenous Se in plants. However, little is known about the exogenous Se application and AMF inoculation on garlic. Here, we evaluated the effects of different concentrations of exogenous Se on the growth, nutritional quality, and selenium enrichment of garlic. The results demonstrated that significantly higher Se content of garlic bulb was found in exogenous Se treated plants, and the Se accumulation was improved with the increasing of Se supply. Low application of exogenous Se appreciably improved the yield and the contents of soluble sugar and allicin in garlic bulbs, but the opposite was observed at high Se concentration. Furthermore, AMF inoculation significantly reduced the inhibition effect of high concentration Se on garlic. AMF supply was effective in improving the growth and nutritional indicators of garlic, which promoted the exogenous Se utilization rate when combined with 10 mg/L exogenous Se treatment. The results will provide a more theoretical basis for the production of high-quality selenium enrichment garlic.

The strategic role of phytohormones and arbuscular mycorrhizal fungi (AMF) to overcome various stress conditions is gaining popularity in sustainable agricultural practices. This current study aims to investigate and identify the protective roles of 28-homobrassinolide (HBL) and Glomus versiforme on two cucumber cultivars (salt sensitive Jinyou 1# and tolerant Chanchun mici (CCMC)) grown under saline conditions (100 mM NaCl). HBL and AMF were applied as individual and combined treatments on two cucumber cultivars and their effects were observed on the morphological growth and physiology under control and saline conditions. Findings revealed that the treated plants showed better performance under saline conditions through improved photosynthesis, leaf relative water content, and decreased electrolyte leakage in tolerant cultivar (CCMC) and to a lesser extent in sensitive (Jinyou 1#) cultivar. Comparable differences were noticed in the antioxidant enzymes activity such as superoxide dismutase, catalase, and peroxidase after every 10 days in both cultivars. Treating the plants with HBL and AMF also improved the mineral uptake regulation and lowered sodium concentration in roots compared to that in the non-treated plants. Current findings suggest that the protective role of HBL and AMF involves the regulation of antioxidants and lowers the risk of ion toxicity in the cucumber and hence enhance tolerance to salinity. These results are promising, but further studies are needed to verify the crop tolerance to stress and help in sustainable agricultural production, particularly vegetables that are prone to salinity.