High lithium tolerance of Apocynum venetum seeds during germination

Identification and use of lithium (Li) accumulator plants is a promising strategy to remediate Li-contaminated soil. Apocynum venetum is reported as a Li accumulator. However, its tolerance to Li salt during germination is still unknown. The primary aim of this study was to investigate the effects of two Li salts on seed germination of A. venetum. At the same concentrations, germination percentages in LiCl solution were higher than that in Li₂CO₃ solution. At 25 °C, seeds germinated to 4-90% at 0-400 mmol L^-1 LiCl and 3-91% at 0-150 mmol L^-1 Li₂CO₃. Low concentration (0-50 mmol L^-1) of LiCl did not significantly affect germination percentage. The simulated critical value (when germination percentage is 50%) in LiCl solution is 196 mmol L^-1, and 36 mmol L^-1 for Li₂CO₃. Activity of α-amylase, contents of MDA, soluble sugar, and proline were dramatically affected by Li salts, especially at medium and late germination stages. When compared with control, α-amylase activity of seeds under 25 mmol L^-1 LiCl and 10 mmol L^-1 Li₂CO₃ did not show significant difference. Germination percentage and index, radicle length, and physiological parameters indicate A. venetum seeds are highly tolerant to Li salts during germination, especially LiCl.