| In this thesis,the change of biological properties of Cinnamomum camphora(L.) Presl seed during development,the difference of desiccation sensitivity and the relative physiological-biochemical mechanism of mature seeds under different drying conditions at room temperature were examined. The effect of stratification under at different low temperature on seed germination and the changes of correlated physiological-biochemical characteristics were also investigated.The whole growth period of Cinnamomum camphora(L.) Presl seed is about 210 d.During development,the biological properties of seed including the color of fruit,fresh weight (FW) and dry weight(DW),moisture content etc undergo remarkable changes:the size of fruit comes to the maximum with the diameter of 0.98 cm as seed developed to 150 DAA(Days after anthesis),but the seed continues to grow up until it reaches physiological maturation at 210 DAA,at that time the fruit becomes black and shining,fresh weight(FW) and dry weight (DW) per 1000 seeds are about 186.42 g and 138.90 g respectively, and seed moisture content is approximately 0.33 gH2O·g-1 DW.Cinnamomum camphora(L.) Presl seeds were dehydrated by silica gel(rapid drying) and nature wind drying(slow drying). During the period of drying,the relationship between the speed of dehydration and seed desiccation tolerance or sensitivity were evaluated by investigating the changes of seed germination,vigor index,electrolytic conductivity of seed soaked solution,contents of storage materials such as soluble sugars,proteins and of the activity of some enzymes etc.The results showed that either by silica gel drying(rapid drying, RD) or by natural wind drying(slow drying,SD) at room temperature,electrolytic conductivity of seed soaked solution presented a tendency of gradually ascending.However, the extent of dehydration through different drying patterns threw different effects on seed germination,responding to the initial slight desiccation(down to about 0.25gH2O·g-1 DW), seeds reached a higher germination percentage of 90.0%and 67.0%with the treatment of RD and SD respectively;As seed germination percentage increased,SOD,CAT,POD activity also rose quickly;But following the extent of desiccation exacerbated,seed vigor declined gradually;at the same time, the content of MDA of seed steeply rose,the activity of SOD,CAT,POD of seed descended,and electrolytic conductivity of seed soaked solution kept elevating.It was suggested that companied by aggravated dehydration,the system of safeguard enzymes were destroyed,free radicals in seed could not be removed in time,membrane lipid peroxidation,and membrane integrity were accelerated and finally caused seed vigor gradually declining.However,at the time seed moisture content dropped towards a steady status,the seed germinat ion percentage was still higher than that of those prior to desiccation treatment,the reason for it might be the case that C.camphora seed has dormancy to certain extent,and dehydration can release seed dormancy;on the other hand,C. camphora(Linn.) Presl seed possesses desiccation tolerance to a certain degree,though seed became injured seriously by further dehydration after seed moisture content was less than 0.25 g H2O·g-1DW,and the seeds withstanding SD suffered more serious damage comparing to those desiccated by RD to the same moisture content.Sand stratification at low temperature above 0℃can release dormancy of C.Camphors(Linn.) Presl seeds effectively,the stratification time for seeds reaching to the maximum germination percentage shortened at higher temperature,but after that time their vigor declined more rapidly;while those seeds stratified in sand below 0℃died quickly.It was suggested that substances which may impede seed to germinate were excluded or broke down effectively during the stratification,which initiated the physiological program of germination of C.Camphora(Linn.) Presl seeds. |
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