Oenothera biennis with strong copper toxicity resistance enriches trace copper in seeds under copper pollution soil.

Excess copper (Cu) imparts negative effects on plant growth and productivity in soil. To develop the ability of O. biennis to govern pollution soil containing excessive Cu, we investigated seed germination, seedling growth, and seed yield. Furthermore, Cu content and the expression levels of Cu transport related genes in different tissues were measured under exogenous high concentration Cu. O. biennis seeds were sensitive to excess Cu, with an observed reduction in the germination rate, primary root length, fresh weight, and number of seeds germinated daily. Consecutive Cu stress did not cause fatal damage to evening primrose, yet it slowed down plant growth slightly by reducing the leaf water, chlorophyll, plant yield, and seed oil contents while increasing the soluble sugar, proline, malondialdehyde, and H2O2 contents. The Cu content in different organs of O. biennis was disrupted by excess Cu. In particular, the Cu content in O. biennis seeds and seed oil increased and subsequently decreased with the increase of exogenous Cu, reaching a peak under 600 mg·kg-1 consecutive Cu. Furthermore, the 4-month 900 mg·kg-1 Cu treatment did not induce the excessive accumulation of Cu in peels, seeds, and seed oil, maintaining the Cu content within the range required by the Chinese National Food Safety Standards. The treatment also resulted in an upregulation of Cu-uptake (ObCOPT5, ObZIP4, and ObYSL2) and vigorous efflux (ObHMA1) of transport genes, of which expression levels were significant positive correlation (p < 0.05) with the Cu content. Among all organs, the stem replaced the root as the organ exhibited the greatest ability to absorb and store Cu, and even the Cu transport genes could still function continuously in stem under excess Cu. This work identified a species that can tolerate high Cu content in soil while maintaining a high yield. Furthermore, the results revealed the enrichment of Cu to occur primarily in the O. biennis stem rather than the seeds and peel under excess Cu.

Effects of Ge-132 and GeO2 on seed germination and seedling growth of Oenothera biennis L. under NaCl stress.

To investigate the effects of ß-carboxyethyl germanium sequioxide (Ge-132) and germanium dioxide (GeO2) on improving salt tolerance of evening primrose (Oenothera biennis L.), seed germination, seedling growth, antioxidase and malondialdehyde (MDA) were observed under treatments of various concentrations (0, 5, 10, 20, 30 µM) of Ge in normal condition and in 50 mM NaCl solution. The results showed that both Ge-132 and GeO2 treatments significantly increased seed germination percentage and shoot length in dose-dependent concentrations but inhibited early root elongation growth. 5-30 µM Ge-132 and 10, 20 µM GeO2 treatments could significantly mitigate even eliminate harmful influence of salt, representing increased percentage of seed germination, root length, ratio between length of root and shoot, and decreased shoot length. These treatments also significantly decreased peroxidase (POD) and catalase (CAT) activities and MDA content. The mechanism is likely that Ge scavenges reactive oxygen species - especially hydrogen peroxide (H2O2) - by its electron configuration 4S24P2 so as to reduce lipid peroxidation. This is the first report about the comparison of bioactivity effect of Ge-132 and GeO2 on seed germination and seedling growth under salt stress. We conclude that Ge-132 is better than GeO2 on promoting salt tolerance of seed and seedling.