Effects Of Soybean Seed Size On Germination Growth,Physiological And Photosynthetic Characteristics

Seed size is an important quality trait of crops and one of the key factors affecting crop yield.The purpose of this paper is to investigate the effect of different-sized seeds on the growth,development,and yield of soybeans.This experiment was conducted in 2022 at the on-campus experimental site of Northeastern Agricultural University and the off-campus Xiangyang experimental site.Four grain classes,large,medium,small,and very small,were set up with Kenfeng 16 and Heinong 84 as test varieties,and the effects of different grain classes on soybean germination characteristics,morphological characteristics,dry matter accumulation,photosynthetic characteristics,physiological characteristics,grain development,and yield were investigated.The main results were as follows:（1）Seed size has an effect on the germination characteristics of soybeans.The performance of Kenfeng 16 and Heinong 84 tends to be consistent under different cropping conditions.The germination potential of very small seeds was the lowest,and there was no significant difference between other seed sizes.The germination rate was higher for large and medium seeds and lower for very small seeds.The germination index was large>medium>small>very small.The vigor index was the highest for large seeds and the lowest for very small seeds.（2）Seed size had a significant effect on the morphological characteristics of soybean.The performance of Kenfeng 16 and Heinong 84 tends to be consistent under different cropping conditions.The seedling emergence rate of large and medium seeds was higher than that of other seed sizes,and the seedling emergence rate of very small seeds was the lowest.Plant height was significantly higher for large and medium seeds than for very small seeds in the early stage of growth,and the difference between seed sizes was not significant in the late stage of growth.Leaf area also showed a gradual increase with increasing seed size,with the highest leaf area for large seeds and the lowest leaf area for very small seeds.（3）Seed size had a significant effect on dry matter accumulation in soybeans.The performance of Kenfeng 16 and Heinong 84 tends to be consistent under different cropping conditions.The overall dry matter accumulation among the whole plant and above-ground parts（leaves,stalks,petioles,and pods）was higher for large and medium seeds,followed by small seeds,and lowest for very small seeds.The overall dry matter accumulation among the roots was highest for large seeds and lowest for very small seeds.no significant trend in root-to-crown ratio change.（4）Seed size has a significant effect on the physiological characteristics of soybeans.The performance of Kenfeng 16 and Heinong 84 tends to be consistent under different cropping conditions.Soybean soluble sugar content,soluble protein content,and proline content were all shown to be higher in large and medium seeds,followed by small seeds,and lowest in very small seeds.Both soybean superoxide dismutase activity and peroxidase activity as a whole showed large seed>medium seed>small seed>very small seed.Malondialdehyde content showed very small seed>small seed>medium seed>large seed.（5）Seed size had a significant effect on the photosynthetic characteristics of soybean.The performance of Kenfeng 16 and Heinong 84 tends to be consistent under different cropping conditions.Relative chlorophyll content（SPAD）was highest in large seeds and lowest in very small seeds.Quantum yields of steady-state fluorescence（Fs）,non-photochemical burst（NPQt）,and regulated energy dissipation（Phi NPQ）were all shown to be higher in large and medium seeds and lower in small and very small seeds.Initial fluorescence（F₀）overall showed very small>small>medium>large seeds.（6）Seed size had a significant effect on soybean yield.The performance of Kenfeng 16 and Heinong 84 tends to be consistent under different cropping conditions.There was no significant difference in the number of very small pods,and the overall numbers of two,three,and four pods showed large>medium>small>very small.Among the agronomic traits,plant height was lowest for very small seeds,bottom pod height was lowest for large seeds,and there was no significant difference in the number of nodes or internode length.The number of seeds and 100-seed weight were large>medium>small>very small,and the yield was higher for large and medium seeds.