Studies On Response Mechanisms Of Antioxidant System In The Leaves Of Two Sabina Species To Low Temperature Stress

Low temperature stress is a typical environmental stress factor,when the ambienttemperature drops more than a certain boundaries,the growth and development of plants willbe subject to certain restrictions,severe cases can lead to death.In China,the low temperaturechilling injury which has occurred from north to south is a serious natural disaster in theagricultural and forestry production can cause huge losses.In order to explore the impact of low temperature stress on physiological ecology in theleaves of Sabina,the test select3-year-old Sabina chinensis （Lin.） Ant. and Sabina przewalskiiKom.. Seedlings as materials,20℃as control,by measuring relative water content（RWC）,relative electrical conductivity（REC）,the content of chlorophyll（Chl）,dialdehyde（MDA）,hydrogen peroxide（H₂O₂）,carotene（Car）,proline（Pro）,soluble protein（SP）,the activity ofsuperoxide dismutase（SOD）,peroxide matter enzyme（POD）,catalase（CAT）and theirisoenzyme electrophoresis analysis in the leaves of two species under different lowtemperature（4℃,0℃and-6℃）,the changes of RWC and content of Chl,membrane lipidperoxidation,antioxidant enzymes and antioxidants with the treatment temperature（20℃,4℃,0℃and-6℃）reduction and processing time（4d,8d,12d,16d and20d）extended wereanalyzed.The differences between the two species as well as correlations between variationswere analyzed,and response mechanism of antioxidant system in the leaves of Sabina to lowtemperature stress was illustrated.The results showed that:（1）4℃can stimulate the antioxidant system of Sabina chinensis （Lin.）Ant. and0℃isthe critical temperature of Sabina chinensis （Lin.） Ant.,it can tolerate at this temperature for8to12days.While0℃can stimulate the antioxidant system of Sabina przewalskii and-6℃isthe critical temperature of the Sabina przewalskii Kom.,it can tolerate at this temperature for12to16days.（2）Under low temperature stress,a significant negative correlation was found betweenRWC and the content of Chl in leaves of Sabina chinensis （Lin.） Ant. and Sabina przewalskiiKom..They can reduce the RWC in leaves to slow down the physiological metabolism.At thesame time,they increase photosynthesis to sustain metabolic balance.（3） Under low temperature stress,the differences of SOD activity between Sabinachinensis （Lin.） Ant. and Sabina przewalskii Kom. are not significant,POD activity in theleaves of Sabina chinensis （Lin.） Ant. is significantly higher than Sabina przewalskiiKom..Under4℃stress,the differences of CAT activity between Sabina chinensis （Lin.） Ant.and Sabina przewalskii Kom. are not significant,Under0℃stress,CAT activity in the leavesof Sabina chinensis （Lin.） Ant. is significantly higher than the Sabina przewalskii Kom. Whileunder-6℃stress,CAT activity in the leaves of Sabina przewalskii Kom. is significantly higher than Sabina chinensis （Lin.） Ant.,indicating that there is not significant linearrelationship between the three enzymes,the three enzymes with more complex non-linearrelationship play an important role in the process of resistance to low tempeture stress.Theincreasing of the stress intensity and treatment time can damage the antioxidant enzymesystem balanced,so that the membrane lipid peroxidation intensified, more serious lowtempeture stress can cause plant injury increases,and eventually death.（4）Low tempeture stress has a significant impact on the content of protein in the leavesof Sabina chinensis （Lin.） Ant. and Sabina przewalskii Kom..There are many differences ofelectrophoresis pattern between Sabina chinensis （Lin.） Ant. and Sabina przewalskii Kom..Compared with Sabina chinensis （Lin.） Ant.,not only the new emerging enzyme bands butalso the enzyme bands which expression levels have changed,the enzyme bands whichactivity has reduced in the leaves of Sabina przewalskii Kom. are significantly less,however,the enzyme bands which activity has increased in the leaves of Sabina przewalskii Kom. aresignificantly more.So expression of the differences may be important physiological responseof Sabina przewalskii Kom. to tempeture stress.（5）Within the critical range of stress intensity,the plant antioxidant system exists as asignaling molecule,plant resistance to tempeture stress was negatively correlated with contentof SP and positively correlated with the content of Car and Pro.The resistance of Sabinaprzewalskii Kom. to low tempeture stress is greater than Sabina chinensis （Lin.） Ant. in termsof antioxidants signal molecule.To sum up:The resistance of Sabina przewalskii Kom. to low tempeture stress is higherthan Sabina chinensis （Lin.） Ant.,regulation of antioxidant enzymes and antioxidants in theleaves of Sabina przewalskii Kom. is more than Sabina chinensis （Lin.）Ant..