| Yellowhorn(Xanthoceras sorbifolium Bunge)belongs to the genus X.sorbifolium in Sapindaceae,is a unique woody oil-bearing tree species with high comprehensive utilization value in China,which is widely distributed in northwest,north and northeast China.In recent years,China has vigorously developed woody oil-bearing tree species,and X.sorbifolium Bunge is listed as one of the key woody oil-bearing tree species in the north.X.sorbifolium Bunge seeds belong to high oil content seeds,and there will be a certain degree of rapid decline in viability during storage.Therefore,screening high-vigor seeds and exploring the changes of seeds vigor and physiological and biochemical indexes after X.sorbifolium Bunge seeds aging are of great significance to reveal the aging mechanism of X.sorbifolium Bunge seeds.In this study,the seeds of X.sorbifolium Bunge from 10 different provenances were artificially aged at high temperature and high humidity(temperature 45℃,relative humidity 99%)for 0,3,6,9,12 and 15 days,and compared with the aged seeds for 0 days,the germination index and electrical conductivity after aging were determined,and the aging resistance of the seeds of 10 provenances was screened and evaluated by fuzzy membership comprehensive evaluation and cluster analysis.The selected provenances were artificially aged,and the changes of physical and chemical indexes such as antioxidant enzyme activity,content of internal storage substances,accumulation of harmful substances and content of osmotic adjustment substances were measured after aging,so as to explore the effects of aging on X.sorbifolium Bunge seeds.The results are as follows:(1)The germination index and relative conductivity of 10 provenances after aging treatment were determined.The results showed that artificial aging treatment reduced the germination rate,germination potential,germination index and vigor index of X.sorbifolium Bunge seeds to varying degrees,while the average germination days and relative conductivity showed an upward trend.Therefore,during the storage of X.sorbifolium Bunge seeds,the storage temperature and humidity should be reduced as much as possible to prolong the seed life.The aging resistance was evaluated and screened by fuzzy membership function evaluation and cluster analysis.Ten provenances were divided into three grades: aging resistant provenance,normal provenance and sensitive provenance.Two specific extreme provenances were screened out: Tai ’an(TA),Shandong Province,with a comprehensive average membership function of 0.74 and Chifeng(CF),Inner Mongolia,with a comprehensive average membership function of 0.21.The ranking and average membership function values of other provenances are Qingyang(TY)0.69 in Gansu,Zhangjiakou(ZJK)0.68 in Hebei,Xianyang(XY)0.64 in Shaanxi,Changping(CP)0.60 in Hebei,Mudanjiang(MDJ)0.58 in Heilongjiang,Balinzuoqi(BLZ)0.52 in Inner Mongolia and Fuxin(FX)0.41 in Liaoning.(2)Using the selected specific extreme provenances Tai ’an(TA)in Shandong Province and Chifeng(CF)in Inner Mongolia as materials,it was found that the seeds vigor of X.sorbifolium Bunge showed a downward trend compared with the control under different aging time treatments,in which the germination rate of Tai ’an(TA)seeds decreased by 14% compared with the control 85%,and the reduction amount of TTC decreased by 23.64% compared with the control0.55mg;The germination rate of Chifeng(CF)seeds decreased by 42% compared with the control 68%,and the reduction amount of TTC decreased by 48.28%compared with the control 0.29 mg.The relative conductivity of Tai ’an(TA)seeds increased by 30.31% compared with the control 26.9%,and that of Chifeng(CF)seeds increased by 48.02% compared with the control 31.47%.The MDA content of Tai ’an(TA)seeds increased by 7.20nmol/g compared with the control 4.52nmol/g,and that of Chifeng(CF)seeds increased by 10.65nmol/g compared with the control5.91nmol/g,which indicated that artificial aging treatment increased the lipid peroxidation level and biofilm permeability of X.sorbifolium Bunge seeds,which may be the main reason for the decline of seed vigor.(3)The antioxidant enzyme activity,osmotic adjustment substance content and ROS production rate of X.sorbifolium Bunge seeds from two provenances after aging treatment were determined.The results showed that the antioxidant enzyme activity of X.sorbifolium Bunge seeds from two provenances generally showed a downward trend,with a decrease of 23.58-68%,and the antioxidant enzyme of seeds from Tai ’an(TA),an anti-aging provenance,could effectively control the balance of active oxygen and maintain seed vitality.Soluble sugar content and soluble protein content generally showed a downward trend;However,the proline content showed an upward trend.The proline content of Tai ’an(TA)seeds increased by 313.43μg/g compared with the control 56.64μg/g,and that of Chifeng(CF)seeds increased by 120.64μg/g compared with the control 88.49μg/g;The production rate of reactive oxygen species showed a downward trend and then an upward trend.The results showed that although aging treatment increased the content of protective substances,with the extension of aging time,the activity of antioxidant enzymes decreased,and the decrease of internal storage substances led to the accumulation of harmful substances,which eventually accelerated seeds aging.(4)Principal component analysis of physical and chemical indexes of X.sorbifolium Bunge seeds after aging showed that the cumulative contribution rate of the first three principal components reached 87.122%.The first principal component feature vector was characterized by the activity of glutenin-sensitive peptide reductase,malondialdehyde content and relative conductivity,the second principal component feature vector was characterized by the content of soluble protein and proline,and the third principal component feature vector was characterized by the production rate of active oxygen.Correlation analysis of physical and chemical indexes and vigor indexes of Tai ’an(TA)and Chifeng(CF)seeds was made.Combined with principal component analysis,it was concluded that the activity and relative conductivity of Glutenin-Sensible Reductase could be the most important indexes to measure the vigor level of X.sorbifolium Bunge seeds,and malondialdehyde content and proline content could be the most important indexes to measure the vigor level of X.sorbifolium Bunge seeds. |
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