Background Cadmium (Cd) is amongst the most toxic heavy metals that severely affects crop growth, whereas application of nanoparticles (NPs) to negate the toxic effects of heavy metals could be an effective management approach. In the present study, the seeds of two fragrant rice varieties i.e., Yuxiangyouzhan and Xiangyaxiangzhan under normal and Cd stress conditions i.e., 0 and 100 mg L− 1 applied with four levels of ZnO NPs i.e., 0, 25, 50, and 100 mg L− 1. Results Seed priming with ZnO NPs had no significant effect on the seed germination (p > 0.05) however, it substantially improved the seedling growth and other related physiological attributes under the Cd stress. The mean fresh weight of the shoot, and whole seedling was increased by 16.92–27.88% and by 16.92–27.88% after ZnO NPs application. The root fresh weight, root-shoot length was also substantially improved under ZnO NPs treatment. Moreover, application of ZnO NPs induced modulations in physiological and biochemical attributes e.g., the superoxide dismutase (SOD) activity in root and shoot, the peroxidase (POD) activity and metallothionein contents in root were increased under low levels of ZnO NPs. The α-amylase and total amylase activity were improved by ZnO NPs application under Cd Stress. Besides, modulation in Zn concentration and ZnO NPs uptake in the seedling were detected. The metabolomic analysis indicated that various pathways such as alanine, aspartate and glutamate metabolism, phenylpropanoid biosynthesis, and taurine and hypotaurine metabolism were possibly important for rice response to ZnO NPs and Cd. Conclusion Overall, application of ZnO NPs substantially improved the early growth and related physio-biochemical attributes in rice. Our findings provide new insights regarding the effects of ZnO NPs on seed germination, and early growth of rice, and its potential applications in developing crop resilience against Cd contaminated soils.

The effect of light and water on aromatic rice remain largely unclear. A pot experiment was conducted to investigate the influences of light-water treatments (CK: natural light and well-watered conditions, WS: natural light and water-stressed conditions, LL: low light and well-watered conditions, LL-WS: low light and water-stressed treatment) on yield and 2-acetyl-1-pyrroline (2AP) formation in aromatic rice. Compared with CK, the light-water treatments decreased grain yield (10.32–39.19%) due to reductions in the filled grain percentage and total dry weight, in the regulation of biomass distribution, and in the attributes of gas exchange and antioxidant response parameters. The 2AP content in grains increased in the LL treatment (5.08–16.32%) but decreased in the WS treatment compared with that in CK. The changes in 2AP were associated with changes in 2AP formation-related traits and element content. Low light and water stress led to yield declines in aromatic rice, but low light alleviated the decrease in 2AP content caused by water stress.

Melatonin and catechol regulate plant growth, but their effects on early growth of fragrant rice and related physio-biochemical attributes under Cd stress are rarely studied. A pot experiment was conducted to evaluate the effects of exogenous melatonin, i.e., 0 and 100 μmol L −1 , and catechol, i.e., 0 and 20 μmol L −1 , application regarded as M0, M100, C0, and C20, respectively, on early growth and physio-biochemical attributes of two fragrant rice cultivars, i.e., Yuxiangyouzhan and Xiangyaxiangzhan. Both rice cultivars were grown under two Cd levels, i.e., 0 and 150 μmol L −1 denoted as Cd0 and Cd150, respectively. Melatonin application improved the dry weight of rice seedlings due to modulations in the growth and antioxidant response under Cd-induced toxicity. The superoxide dismutase (SOD) and peroxidase (POD) activities in root were increased, whereas malondialdehyde (MDA) content in root and shoot was decreased with melatonin application. Catechol also regulated the growth and antioxidant response of fragrant rice seedlings under Cd-induced toxicity. The interactive effects of melatonin and catechol, i.e., M100 + C0 treatment resulted in the maximum plant dry weight, whereas the M100 + C0 + Cd150 treatment resulted in the lowest Cd concentration in roots and shoots of Xiangyaxiangzhan as well as in roots of Yuxiangyouzhan. Furthermore, multivariate analysis revealed that the POD activity in root was an important limiting factor for fragrant rice seedlings to mitigate Cd-induced toxicity. Overall, melatonin and catechol could modulate the early growth and antioxidant response of fragrant rice seedlings under Cd-induced toxicity.

Background: Cadmium (Cd) is among the most toxic heavy metals that severely affects crop growth, and in this purview numerous recent research initiatives have focused on the application of nanoparticles (NPs) to negate the toxic effects of heavy metals such as Cd. Method: In the present study, the seeds of two fragrant rice cultivars, namely Yuxiangyouzhan and Xiangyaxiangzhan, were grown after exposure to four ZnO NPs treatment (0, 25, 50, and 100 mg L-1), with or without the presence of Cd (100 mg L-1). Result: The results revealed that priming seeds with ZnO NPs had no significant effect on the seed germination (p > 0.05) however, it substantially improved the seedling growth and other related physiological attributes under the Cd stress. The mean fresh weight of the shoot, and whole seedling increased after ZnO NPs treatment by 16.92%-27.88% and 12.82-33.58%, respectively. The fresh weight of root, length of the shoot, and the root increased after ZnO NPs treatment. Moreover, remarkable changes in the physiological response of seedlings under ZnO NPs treatment were detected. The metabolomic analysis was performed to discern the underlying regulation of the metabolisms after ZnO NPs treatment for seedlings under Cd stress. Conclusion: Our findings provide new insight into the influence of ZnO NPs on seed germination, and the growth of crop plants, and may find potential applications in developing crop resilience in Cd laden agricultural lands.