Analysis Of The Physiological Characteristics Of Germination And Dormancy Of Two Lepidium Species And Establishment Their SRAP System

Lepidium apetalum Wild.and Lepidium perfoliatum L.are two genetically related and differently distributed ephemerals species in Xinjiang.Our previous study also found their different tolerance to low temperature during seed germination and seedling growth.In order to elucidate the differences during seed dormancy and germination,the physiological and biochemical characteristics of dormancy and dormancy release were analyzed in two Lepidium species,and a sequence related amplified polymorphism(SRAP)analysis system was established.1 The effects of cold stratification on the germination of two species were compared and the changes of enzyme activities such as peroxidase(POD)superoxide dismutase(SOD)and catalase(CAT)in the process of stratification were determined.The results showed that cold stratification leads to dormancy release and germination in Lepidium perfoliatum L.whereas only improves germination potentialin Lepidium apetalum Wild.Changes of enzyme activities during cold stratification were detected in both species although showed different patterns.The results suggested that the dormancy release of two species has different response to low temperature stratification.In addition,the germination experiments of Chinese cabbage seeds treated with extracts from different parts of Lepidium perfoliatum L.seeds showed that the dormancy of Lepidium perfoliatum L.seeds is probably due to the presence of germination inhibitors in embryo.2 The changes of gibberellin(GA)and abscisic acid(ABA)level in the seeds of two species during cold stratification were determined by high performance liquid chromatography.The results showed that changes of endogenous hormones level display a same pattern during stratification in seeds of two species as the content of GA increased whereas ABA decreased,and the level of ABA was higher in Lepidium perfoliatum L.seeds before bedding when GA was higher in Lepidium apetalum Wild.seeds.The results suggested the important roles of GA and ABA in seed dormancy release of two species.3 The effects of exogenous hormones on the dormancy and germination of two species were studied.IAA and NAA could partially release dormancy in Lepidium perfoliatum L.seeds but inhibit germination in Lepidium apetalum Wild.GA could promote germination of both two species mean while completely release dormancy of Lepidium perfoliatum seeds.6-BA has no effect on dormancy release of Lepidiumperfoliatum L.,and has double effects on germination of Lepidium apetalum Wild..ABA significantly inhibited the germination of both two species.The results showed that the dormancy release process of two species has different responses to hormones.4 In order to establish a SRAP analysis system suitable for seeds of two species,the impact of content of dNTPs,Mg2+,primers,cDNA templates and Taq DNA polymerase on the amplification effect were analyzed and optimized.Finally,the optimized cDNA-SRAP system is as follows: 100 ng cDNA template,1.75 mmol.L-1Mg2+,0.275 mmol.L-1dNTPs,1 ?mol.L-1primers and 0.5 U Taq DNA polymerase in a total volume of 20 ?L reaction system.The polymorphism and resolution of the amplified bands may be qualified to study gene differential expression of two species under cold stratification.