Seed Semipermeability Of Several Poaceae Species And Their Relation To Seed Quality Determination

Seed semipermeable layer could be defined as an important layer in the embryo porcket,allowing water and gas to be freely exchanged internally and externally,while limiting or preventing the penetration of certain solutes.The presence,location and chemical composition of semipermeable layer have been reported a few in the before researches,however,there are few studies on comparing the semipermeable differences between different species and the relationship between semipermeable characteristics and seed quality evaluation.In this research,total seven poaceae species were stuied,including Triticum aestivum,Oryza sativa,Zea mays,Setaria italica,Sorghum bicolor,Panicum miliaceum and Sorghum bicolor × Sorghum sudanense.Using lanthanum nitrate tracer combined with scanning electron microscopy and X-ray energy dispersive analysis,and differnet fluorescent tracers,the interspecies and intraspecial differences of the seed semipermeability were studied.Compared the results of different tracers,discussed the presence and position of the semipermeable layer among species,and the relationship between seed semipermeability and seed quality determination.It aims to understand the difference of seed semipermeability in different plant species and its function,to provide a scientific basis for a more suitable seed quality evaluation methods.Here's the main results:1 The results of the different tracer techniques were not completely consistent for evaluating the seed semipermeability of 7 poaceae species,but the results of lanthanum tracer showed that all species had semipermeable layer.That is,the seed coat of 7 kinds of poaceae plants are water permeated,but restricted the permeability of lanthanum.The semipermeable layer were located in seed coat in wheat,rice,maize and foxtail millet while in the endosperm in sorghum,proso millet and sorghum hybrid sudangrass.2 The results of the different tracer techniques were also not completely consistent for evaluating the seed semipermeability of three varieties of sorghum hybrid sudangrass.But the results of lanthanum tracer showed that a semipermeable layer presented in sorghum hybrid sudangrass seeds.It is further proved that lanthanum is a stable tracer in seed semipermeable layer research.3 The results of tetrazolium salt staining on seed viability tests showed that seed semipermeability was the limiting factor that affect seed viability test,and the limitinig varies with species.Rice had seed coats that allowed uptake of tetrazolium,tetrazolium salt staining can be used directly in intact rice seeds viability test.While the other 6 plant species had a high degree of impermeability to tetrazolium salt uptake,tetrazolium salt staining method can be used seed viability test after punctured.4 The results showed that seed semipermeability was the limiting factor for seed vigour test for some species.Electrical conductivity(EC)methods can be used to test seed vigour of rice,maize and proso millet directly.The correlation coefficient between seed vigour and EC is-0.9384,-0.9657,-0.9323,for rice,maize and proso millet respectively.While wheat,foxtail millet,sorghum and sorghum hybrid sudangrass seeds need to be punctured,before testing seed vigour by EC.For example,aged wheat seeds,the correlation between seed vigour and EC for intact seeds were nor relevant(r =-0.3256,P > 0.05).After puncturing the seed coats,seed vigour was negatively correlated with EC(r =-0.9361,P < 0.01).