Plasticity Of Soybean Root Phenotypic Traits And Their Adaptation To Low Phosphorus Stress

Phosphorus is one of the three major mineral nutrients required for the plant growth and development.It participates inmost of basic activities of life and is also one of the main components of fertilizers needed to maintain modern agricultural production and development.Although people apply a large amount of phosphate fertilizers,most of the phosphorus are easily fixed after entered to soil,resulting in low efficiency of phosphate fertilizers,which waste of resources and have a threat to environmente Roots,as a"bridge and link"connecting the above-ground and underground of plants,plays an important role in plant growth and development.In this paper,we analyzed the root traits responses and evaluated the difference of phosphorus efficiency of 78 different genotypes of soybean at seedling stage to low phosphorus stress by using the semi-hydroponic root phenotypic trait observation system.Based on this,two field experiments were conducted to verify the responses of the screened soybean genotypes to low phosphorus stress.The main results are as follows:(1)Harvested at 21 days after transplanting to the semi-hydroponic system,the root traits of 78 different genotypes of soybean was significantly different(CV≥0.25).The variation range of total root length was 1.1-41.76 m(average 15.62 m),and the variation range of root surface area was 12.02-321.04 cm~2 on average(average 119.96 cm~2).Phosphorus treatments and genotypes indicated no significant interaction on root length,but significantlyimpact on total root length,root surface area,root volume and root dry weight(P<0.05).Low phosphorus stress significantly inhibited the total root length of low phosphorus sensitive genotype soybean(#65,Xudou 14),decreased by 41%,but promoted the total root length(#25,Jidou 12;#30,Xudou 18).Phosphorus-efficient genotypes improved the efficiency of phosphorus uptake by promoting the elongation of root system,which is manifested in the increase of total root length,root surface area and root volume.In addition,the phosphorus-efficient genotype soybean also promoted soybean growth by improving nitrogen absorption,thereby reducing the impact of low phosphorus stress.(2)Based on total biomass,total root length,total phosphorus content,physiological phosphorus use efficiency and phosphorus effective ratio as screening indicators,5phosphorus efficiency genotypes(Dongdou 88,Jidou 12,Xudou 18,Wandou 15 and Shidou7)and 5 phosphorus sensitive genotypes(Shandong farm soybean,soybean high-yield research,Jindou 888,Guandou 1,Xudou 14)were screened out from 78 soybean varieties at seedling stage.Low phosphorus stress significantly reduced the total phosphorus content,phosphorus concentration and total nitrogen content of soybean.(3)Two field experiments were conducted on Caoxinzhuang and Qianxian County by using the tensoybean varieties(5 high phosphorus efficiency and 5 low phosphorus efficiency varieties)screened out in the semi-hydroponics experiment.The results showed that the field experiment were consistent with the hydroponic experiment.Under the low phosphorus stress,the soybean genotype with high phosphorus efficiency increased the total root length by increasing the length of the lateral root,which improved plant growth,phosphorus efficiency,and enhanced the ability to resist the low phosphorus stress.Present study investigated the root morphology and phosphorus efficiency responses of78 soybeanvarieties to low phosphorus stress by using a semi-hydroponic device.Combined with the total biomass,total root length,total phosphorus content,physiological phosphorus use efficiency and phosphorus effective ratio of soybean seedlings,Dongdou 88,Jidou 12,Xudou 18,Wandou 15 and Shidou 7 were screened as phosphorus-efficient genotypes,Shandong farm soybean,soybean high-yield research,Jindou 888,Guandou 1 and Xudou 14were phosphorus inefficient genotypes.It was revealed that the phosphorus-efficient genotype could respond to low phosphorus stress by changing root morphology such as total root length,root surface area,and root volume.Some of the research results have certain practical guiding significance for agricultural production in theory and practice.