Screening Of High Cd Accumulation Germplasms And Physiological Analysis Of Cd Tolerance In Ramie(Boehmeria Nivea L.)

Soil Cd contamination,with high bioavailability,occurs widely in China and accumulates through food chain,thus posing a significant threat to food safety.The techniques available for remediating the soil contaminated by Cd are costly or time consuming,which limits their application.Ramie?Boehmeria nivea L.?is considered suitable to be planted in Cd contaminated soils because of its high Cd tolerance,high biomass,and non-food products.Previous studies have measured few varieties,which are lack of thorough understanding of genotypic difference.Besides,the variety screening is time consuming because ramie is perennial.Focusing on these issues,195 germplasm resources of ramie were selected and potted experiments were conducted both in hydroponics and soil under Cd stress.High Cd absorbing germplasms were screened and quick screening method was studied.Physiological responding characteristics were analyzed under Cd stress based on distinct germplasms selected.The results showed that:?1?When the ramie seedlings were cultured in the clean water with tender shoots,the 4^th or 5^th day after cuttage was the best time to add nutrient solution,which was beneficial for root.?2?Under the hydroponics condition where cadmium stress was 7 mg/L,the cadmium concentration in roots was the highest,followed by stems and leaves in turn among ramie tested.And the cadmium concentration in roots and stems?except for Zhijiangqingke?were higher than 100 mg/kg.Meanwhile,taking the Cd concentration into consideration,73.34%of the germplasms ranged from 1200 to 4800 mg/kg in their roots,and the percentage ranging from 120 to520 mg/kg in their stems was 85.13%,and 84.10%of the germplasms less than 42 mg/kg in leaves.18 germplasms had potential of absorbing massive cadmium,including Xinninghuangma NO.1,Dayema NO.2,Xiangzhu NO.2,and so on.?3?After being planted in soil?in which the Cd concentration was 80 mg/kg?for 75 days,37 germplasms,chosen from the previous hydroponic experiment,didn't reach the level of hyperaccumulator.?4?Analyzing plant height,dry weight and cadmium concentration,37 ramie germplasms were divided into 3 groups by means of clustering analysis.3 groups were group H&H?high yield and high absorption?,group L&H?low yield but high absorption?,and group L&L?low yield&low absorption?.4 germplasms in group H&H and L&H were evaluated as excellent species with good comprehensive characteristics,including Xiangzhu NO.2,Daxianhuangma NO.2,Sichuan 6-1 Baitou,Wushanxiangdongxianma.?5?Cd-resistance ramie germplasms responded to persistent Cd stress by increasing the contents of soluble protein in roots and leaves,maintaining high active absorption area of root and increasing chlorophyll content.Among 3 of the materials,the active absorption area of root of Shaoyang NO.3 was highest,as the potential of absorbing Cd was higher.