Seed Germination Characteristics Of Caragana Species With Geographical Alternate Distribution

Caragana Fabr.is leguminous shrub widely distributed in desert,grassland and forest areas in China,which has important ecological and economic value.In this paper,C.korshinskii distributed in arid regions,C.intermediate and C.microphylla distributed in semi-arid areas,C aborescens and C.boisi distributed in semi-humid areas,and C.stipitata distributed in humid areas were used to explored the seed morphology,seed coat structure,water permeability,and ABA content.Taking this as the standard to reveal the difference in seed germination,and the difference in seed coat structure promots the germination of seeds.The main results are as follows:1.Germination rate of C.korshinskii distrbuting in arid regions has a strong germination ability,which is more than 90 %,while the seeds of C.stipitata in humid areas were dormant and did not germinate.The seed germination rate exhibited a significant decline from the arid to the humid regions.2.The seeds of C.korshinskii distrbuting in arid regions had low endogenous ABA concentration than C.stipitata distrbuting in humid regions.Furthemore,the increasing of endogenous ABA in seeds from the arid region to the humid region,and it produced a negatively correlated with the maximum seed germination rate in each species.The seeds germination rate of C.stipitata increased from 0 % to 53.3 % ?26.7 % and 30.0 % after treated with the ABA antagonist gibberellin(GA3),ABA synthesis inhibitor(fluridone)and dihydroguaiaretic acid(NDGA).However,the seeds germination rate of C.korshinskii was reduced by half after treated with the ABA decomposition inhibitor(Uniconazole).Those results all confirmed that ABA inhibited the germination of Caragana seeds.3.The seeds epidermal structure of C.korshinskii,C.intermedia and C.microphylla distributed in arid environment was loose,and the stone cells between epidermis and epidermis had obvious tubular structures;However,C.aborescens,C.boisi and C.stipitata distributed in the semihumid and humid regions was dense,and the stone cells between the epidermis and the lower epidermis had obvious sheet-like structure.Water dye absorption indicated that the seed coats distributed in the arid environment were water-absorbing quickly,on the contrary,and the seed coats distributed in the humid environment were not water-absorbent,which restricted the germination of seeds.4..Spraying water on the suface of seeds of C.korshinskii,the seeds epidermis absorbs condensate formed water rapidly,at same time,the germination rate is twofold higher than control level when the soil relative water content maintained at 20 %.Those shown that condensed water significantly promoted the seeds germination of species distrbuted in arid regions.