Effects of Soil Arsenic on Soybean Main Traits and Chlorophyll Content at Different Growing Stage

Abstract

Arsenic is ubiquitous in environment and has high toxicity to animal and plant.Investigating the effects of arsenic on plant growth is important for the recognition of the toxic mechanism of arsenic to plant and the food safety.To understand the relationship between soil arsenic pollution and plant growth,we conducted a soil pot experiment using a soybean variety with adding different amounts of arsenic into soil,in which the soybean growth condition was observed and the plant height,chloro-phyll content at podding and grain filling stages and the biomass after harvest were determined.The results showed that visible symptom of arsenic toxicity to soybean was dwarfing of plants,dark green and crimpled leaves,retarded maturity when soil arse-nic addition was up to 50 mg kg-1.The soybean plant height decreased and the soybean biomass significantly reduced when high soil arsenic contents.The soybean plant height,soybean stem biomass,aerial part biomass,grain yield and the total soybean bio-mass decreased by 45.0%,36.6%,44.6%,56.1%,and 43.4%,respectively,in the treatments of 100 mg kg-1 of arsenic.High soil arsenic amounts increased the biomass ratios of roots to aerial parts and stems to aerial parts,but decreased the ratios of grains to aerial parts,grains to stems and grains to total biomass.Soil arsenic amounts had no significant effects on chlorophyll content in soybean leaf but decreased the ratio of Chl a to Chl b at podding stage.At grain filling stage,50 and 100 mg kg?1 arsenic treat-ments increased 120.4% and 96.1% of Chl a,112.2% and 91.5% of Chl b,117.8% and 94.5% of total chlorophyll and 104.4% and 83.7% of carotenoid content,respectively.High soil arsenic amounts reduced the ratio of chlorophyll content at podding stage to that at grain filling stage significantly.In conclusion,high soil arsenic amounts are toxic to soybean growth,affect the allocation of soybean biomass,and decrease the biomass of aerial parts and grains yield.The important reason of the retardation of soybean maturity is the constitutional alteration of chlorophyll in soybean leaf and the relative increment of chlorophyll content in soybean leaves during later growing stage by high soil arsenic amounts.