Although the sources of molecular hydrogen (H₂) synthesis in plants remain to be fully elucidated, ample evidence shows that plant-based H₂ can regulate development and stress responses. Here, we present genetic and molecular evidence indicating that nitrate reductase (NR) might be a target of H₂ sensing that positively regulates nitrogen use efficiency (NUE) and seed size in Arabidopsis (Arabidopsis thaliana). The expression level of NR and changes of NUE under control and, in particular, low nitrogen supply, were positively associated with H₂ addition supplied exogenously or through genetic manipulation. The improvement in nitrate assimilation achieved by H₂ was also mediated via NR dephosphorylation. H₂ control of seed size was impaired by NR mutation. Further genetic evidence revealed that H₂, NR, and nitric oxide can synergistically regulate nitrate assimilation in response to N starvation conditions. Collectively, our data indicate that NR might be a target for H₂ sensing, ultimately positively regulating nitrate uptake and seed size. These results provide insights into H₂ signaling and its functions in plant metabolism.

A reliable and stable hydrogen gas (H₂) supply will benefit agricultural laboratory and field trials. Here, we assessed ammonia borane (AB), an efficient hydrogen storage material used in the energy industry, and determined its effect on plant physiology and the corresponding mechanism. Through hydroponics and pot experiments, we discovered that AB increases tomato (Solanum lycopersicum) lateral root (LR) branching, and this function depended on the increased endogenous H₂ level caused by the sustainable H₂ supply. In particular, AB might trigger LR primordia initiation. Transgenic tomato and Arabidopsis (Arabidopsis thaliana) expressing hydrogenase1 (CrHYD1) from Chlamydomonas reinhardtii not only accumulated higher endogenous H₂ and phytomelatonin levels, but also displayed pronounced LR branching. These endogenous H₂ responses achieved by AB or genetic manipulation were sensitive to the pharmacological removal of phytomelatonin, indicating the downstream role of phytomelatonin in endogenous H₂ control of LR formation. Consistently, extra H₂ supply failed to influence the LR defective phenotypes in phytomelatonin synthetic mutants. Molecular evidence showed that the phytomelatonin-regulated auxin signaling network and cell cycle regulation were associated with the AB/H₂ control of LR branching. Also, AB and melatonin had little effect on LR branching in the presence of auxin synthetic inhibitors. Collectively, our integrated approaches show that supplying H₂ via AB increases LR branching via phytomelatonin signaling. This finding might open the way for applying hydrogen storage materials to horticultural production.

Bok choy (Brassica rapa var. chinensis) experiences rapid postharvest quality decline, primarily due to water loss. This study aims to evaluate the effect of H₂-modified atmosphere packaging (MAP; containing 0.01%, 0.1%, and 1% H₂) on extending the shelf life of bok choy. First, we observed that the storage of bok choy for 9 d (4 °C and 85% relative humidity) was accompanied by a decreasing tendency of molecular hydrogen (H₂) production. Subsequently, the effects of hydrogen (H₂) administered via modified atmosphere packaging on the preservation of bok choy were investigated. The results showed that among the treatments, 0.1% H₂ MAP could effectively improve the storage quality of bok choy under identical storage conditions. Compared to the control groups at 9 d, the contents of chlorophyll a/b, carotenoids, total phenols and flavonoids, and total soluble solids were increased by 43.75%, 40%, 27.78%, 28.89%, 102.38%, and 7.29%, and weight loss rate and electrolyte leakage were reduced by 31.77% and 50.19% (p < 0.05). Meanwhile, the combined water fraction was increased and respiration rate was decreased. Biochemical evidence further showed that xyloglucan endotransglycosylase 2/3 (XET2/3) transcripts and xyloglucan endotransglycosylase (XET) activity, responsible for cell wall degradation, were decreased. By contrast, peroxidase 31/37 (POD31/37) genes and peroxidase (POD) activity, key to the synthesis of lignin, were increased. Importantly, these changes were positively matched with the maintenance of cell wall integrity by H₂ MAP. Together, the results clearly suggested that H₂ MAP could maintain the postharvest quality of bok choy via alleviating water loss and maintaining cell wall integrity. These findings thus provide a useful technology for improving the storage quality of vegetables prone to water loss.

Simultaneously improving the yield and, in particular, the nutritional quality of sweet corn (Zea mays L. saccharata), one of the most important cereal fresh foods worldwide, remains a major challenge. Here, we demonstrated that compared to control groups, hydrogen-enriched water (HEW) irrigation significantly improved agronomic performance, increasing kernel number (~10.55%) and ear length (~5.73%) while notably reducing barren tip length by about 60.73%. Regarding nutritional quality, HEW-treated kernels exhibited remarkable increases in soluble protein (~61.53%), total soluble sugars (~31.10%), vitamin C (~28.31%), total phenolics (~21.06%), and flavonoids (~40.56%). Micronutrients were also enhanced, such as zinc (~96.82%), iron (~51.70%), and manganese levels (~40.37%). HEW effectively modulated the expression of sugar metabolism-related genes. Specifically, the coordinated upregulation of key genes, such as ZmSUS1 (~3.8 fold), ZmINCW2 (~1.9 fold), and ZmHXK1 (~1.6 fold), might contribute to the enhanced accumulation of sucrose (~11.79%), glucose (~6.21%), and fructose (~26.50%). Starch biosynthesis was also promoted. The improved sugar–acid ratio indicated enhanced taste quality. Importantly, representative key antioxidant genes (ZmSOD2/4, ZmPOD1/2, and ZmCAT1/3) as well as corresponding enzymatic activities in kernels were stimulated, which was negatively associated with lipid peroxidation. Overall, these results indicate that HEW irrigation is a promising, eco-friendly strategy that can be efficiently used to improve sweet corn yield and nutritional value.

Helium, a traditionally inert gas, has garnered interest in medicine, yet its role in plant heavy metal responses is still elusive. Here, we investigated whether or how helium orchestrates rapeseed cadmium (Cd) tolerance. Hydroponic experimental results demonstrated that helium-enriched solution markedly alleviated Cd-induced inhibition of root growth. Importantly, helium-inhibited Cd uptake was evidenced by non-invasive micro-test technology (NMT). By using grafting experiments, we clearly observed differential responses in Cd accumulation. Since shoot tissues had relatively lower Cd contents, the inhibited root-to-shoot Cd translocation might be used to explain the low Cd accumulation achieved by helium. Further analysis indicated that helium enhanced Cd sequestration in root cell walls. Remarkably, Cd-triggered oxidative damage was effectively eliminated via stimulating the antioxidant system. Collectively, these findings suggest that restricted Cd uptake and inhibition in translocation, as well as antioxidant capacity stimulation, might be important mechanisms for helium-orchestrated Cd tolerance, thus providing a potential approach for sustainable agriculture and food security.