Foliar application of seed water extract of Nigella sativa improved maize growth in cadmium-contaminated soil

Differential physiological responses and tolerance to potentially toxic elements in Primula forbesii Franch

Environmental pollution caused by potentially toxic elements (PTEs) has become a global problem that endangers environmental sustainability due to industrial, agricultural, and urban pollution. Primula forbesii Franch. (a synonym of Primula filipes G. Watt.) is a biennial flower native to China with excellent stress resistance and ornamental value. In this study, we examined the phenotypic traits, growth indexes, and physiological properties of P. forbesii in response to five representative PTEs (Cd, Ni, Cr(III), Cu, and Zn) under hydroponic culture conditions. High concentrations of Zn and Cr had little effect on the growth and physiological properties of P. forbesii, indicating that the species has strong tolerance to Zn and Cr stress. Alternatively, high concentrations of Cd, Ni, and Cu seriously affected plant growth and development, resulting in leaf chlorosis and even death, and therefore may have a serious negative impact on the growth of P. forbesii. However, activity levels of some antioxidant enzymes and osmotic regulatory substances remained high, indicating that P. forbesii resisted PTE stress by regulating physiological and biochemical metabolism to a certain extent. Furthermore, principal component analysis and membership function were used to comprehensively evaluate P. forbesii resistance to PTEs. These analyses revealed that P. forbesii exhibits distinct sensitivities and physiological responses to different PTEs and suggested that the resistance to five PTEs in decreasing order is Zn > Cr > Cd > Cu > Ni. These results provide a theoretical basis for the future application of P. forbesii in environments with PTE pollution and may expand its practical utilization.

Proanthocyanidins Alleviate Cadmium Stress in Industrial Hemp (Cannabis sativa L.)

Industrial hemp (Cannabis sativa L.), an annual herbaceous cash crop, is widely used for the remediation of heavy metal-contaminated soils due to its short growth cycle, high tolerance, high biomass, and lack of susceptibility to transfer heavy metals into the human food chain. In this study, a significant increase in proanthocyanidins was found in Yunnan hemp no. 1 after cadmium stress. Proanthocyanidins are presumed to be a key secondary metabolite for cadmium stress mitigation. Therefore, to investigate the effect of proanthocyanidins on industrial hemp under cadmium stress, four experimental treatments were set up: normal environment, cadmium stress, proanthocyanidin treatment, and cadmium stress after pretreatment with proanthocyanidins. The phenotypes from the different treatments were compared. The experimental results showed that pretreatment with proanthocyanidins significantly alleviated cadmium toxicity in industrial hemp. The transcriptome and metabolome of industrial hemp were evaluated in the different treatments. Proanthocyanidin treatment and cadmium stress in industrial hemp mainly affected gene expression in metabolic pathways associated with glutathione metabolism, phenylpropanoids, and photosynthesis, which in turn altered the metabolite content in metabolic pathways of phenylalanine, vitamin metabolism, and carotenoid synthesis. The combined transcriptomic and metabolomic analysis revealed that proanthocyanidins mitigated cadmium toxicity by enhancing photosynthesis, secondary metabolite synthesis, and antioxidant synthesis. In addition, exogenous proanthocyanidins and cadmium ions acted simultaneously on EDS1 to induce the production of large amounts of salicylic acid in the plant. Finally, overexpression of CsANR and CsLAR, key genes for proanthocyanidins synthesis in industrial hemp, was established in Arabidopsis plants. The corresponding plants were subjected to cadmium stress, and the results showed that CsLAR transgenic plants were more tolerant to cadmium than the CsANR transgenic and wild-type Arabidopsis plants. The results showed that salicylic acid and jasmonic acid were increased in Arabidopsis overexpressing CsLAR compared to AT wild-type Arabidopsis, and levels of secondary metabolites were significantly higher in Arabidopsis overexpressing CsLAR than in AT wild-type Arabidopsis. These results revealed how proanthocyanidins alleviated cadmium stress and laid the foundation for breeding industrial hemp varieties with higher levels of proanthocyanidins and greater tolerance.