Effect Of Proanthocyanidins On Germination And Seedling Growth Characteristics Of Alfalfa Under Cadmium Stress

In the southern region of cadmium-contaminated agricultural soils,replacing food crops with cadmium-tolerant forage crops can reduce the transfer of cadmium to the food chain through seed crops and bring certain economic benefits,which is one of the effective measures to balance safety and economy.Alfalfa(Medicago sativa L.),as a high-yield and high-quality forage grass,has the reputation of "the king of forage grass" and is one of the alternative planting options.However,the germination and seedling growth of alfalfa are slow,and cadmium stress can cause problems such as uneven seedling emergence,slow growth and susceptibility to weed infestation in alfalfa.In this study,13 high autumn dormancy grade alfalfa varieties were used as experimental materials to study the inhibitory effects of different Cd stress on alfalfa germination and seedling growth,the promoting effects of different proanthocyanidins(PAs)addition on alfalfa germination growth,and the effects of PAs on alleviating Cd toxicity in alfalfa germination and seedling growth under Cd stress conditions,aiming to explore the feasibility of applying PAs to alfalfa seed coating agents.The main findings were follows.(1)The inhibition of alfalfa germination by different Cd stress concentrations varied.Under moderate Cd stress(50 mg/L),some alfalfa germination potential and germination rate showed an increase compared to the control,but under severe Cd stress concentration(100 mg/L),the germination potential and germination rate of all 13 varieties of alfalfa were inhibited.The inhibition of alfalfa seedling growth by Cd was stronger than the inhibition of seed germination.Both moderate and severe Cd stress significantly inhibited all growth indicators of alfalfa,and the inhibition effect was proportional to the Cd stress concentration.(2)The effects of proanthocyanidins on germintion and seedling growth of different alfalfa varieties were different,and the effects of different proanthocyanidin concentrations on the same alfalfa also differed.In general,proanthocyanidins had a more significant effect on the growth index of alfalfa seedlings,and 75 mg/L proanthocyanidins had the best effect on the germination and seedling growth of 13 varieties of alfalfa.(3)Proanthocyanidins had less alleviating effects on alfalfa germination under cadmium stress,but had varying degrees of alleviating effects on the growth of its seedlings.75 mg/L proanthocyanidin concentration promoted root length,shoot length,surface area,volume and alleviated the swollen root shoot diameter of alfalfa due to stress compared to the treatment without proanthocyanidin addition.