Study On The Changes Of Vigor And Optimum Moisture Content Of Maize Seed Stored At Ultralow Temperature

Cryopreservation is a storage technology that germplasm resources were preserved below the temperature of-80 ?,which commonly was used to preserve breeding materials and germplasm resources.Generally,the cold source of cryopreservation are liquid nitrogen(-196 ?).In this study,5 maize variety seeds of PH6 WC,zheng58,chang7-2,9801 and qi319 were chosen as materials.Each maize variety seeds respectively got 5 water levels(6% ?8%?10% ?12%and14%)by silicone drying and spraying water.Before liquid nitrogen cryopreservation tests were carried out,adequate above-mentioned seeds were taken and stored 7 days at-196 ?,setting the starting moisture seeds preserved under room temperature as CK.Seedling growth test,simulated field germination test,cold water test,electrical conductivity test,and ADH,POD,CAT,SOD,LOX activities test were used to determine the vitality indexes of maize seeds.PH6 WC seeds were used as the materials to carry out seedling growth test ? electrical conductivity test ? simulated field germination test and ADH test after liquid nitrogen cryopreservation in different times and different treatment methods,which were used to test influence of cryopreservation on seed vigor and optimum moisture content of maize seeds stored at-196 ?.The results are as follows:1.The results of commonly seed vigor indicator testing showed:maize seeds of 5kinds of moisture grades after stored in liquid nitrogen for 7d,the treatment which moisture content exceed 10% or below8% declined greatly,while the treatment which moisture content is 8% or 10% had no significant difference compared with control.2.The results of enzyme activities testing showed:maize seeds of 5 kinds of moisture grades after stored in liquid nitrogen for 7d,most seeds' activities of ADH,POD,CAT,SOD and LOX were declined different degree,while a few was got up compared with control.The enzyme activities of treatment 10% and 8% descended smaller and had no significant difference compared with control.3.There were no significant differences of seed vigor indexes between maize seeds after liquid nitrogen cryopreservation in different times,eventhough which were lower than the check.Most major seed vigor indexes of the maize seeds were higher than the check after liquid nitrogen cryopreservation in different treatment methods,and the vigor indexes of muted freeze treatment were higher than the muted thaw treatment.4.In every maize varieties,the average decline of each vigor indicator of two better treatment of 6%~10% indicated: maize varieties' ability of ultra-low temperatureresistance is different,which is from big to small:chang7-2?qi319?zheng58?9801?PH6WC.5.According to the changes of indicators or activities,five maize variety seeds can find an optimum moisture content at ultra–low temperature storage,PH6 WC is 8.07%,zheng58 is 7.91%,chang7-2 is 8.06%,9801 is 7.81%,qi319 is 7.94%.Preliminary view is that maize variety seeds are suitable for ultralow temperature storage,of which the optimum moisture content is about 8%.