| Low temperature is an important factor to limit the geographical distribution of plants,and also one of disaster often encountered in plants growth.The production of agriculture andforestry is seriously affected in most area of our country because of low temperature stress.Inaddition the adaptation of plants to low temperature stress is not only controlled by geneticcharacteristics, the plant hormone can also improve the cold resistance of plant to a certainextent by changing the membrane system through gene regulation or metabolism.The effectof exogenous ABA and SA on membrane lipid peroxidation,osmotic regulation substancesand antioxidant enzyme activities in the leaves of Sabina species under low temperature stressat-4℃was analyzed by determining the relative electrical conductivity(REC), contents ofmalondialdehyde(MDA), soluble protein(SP) and proline(Pro), activities of superoxidedismutase(SOD), peroxidase(POD), catalase(CAT), ascorbic acid peroxidase(APX) andglutathione reductase (GR) in the leaves of3-year-old seedlings of Sabina przewalskii andSabina chinensis pretreated with different concentrations of ABA and SA to investigate thehormone regulation mechanism in the process of the Sabina frost formation and provide atheoretical basis for fostering more anti-freeze evergreen varieties.The results showed that:With stress time prolonging, REC and MDA contents in the leaves of Sabina increased,plants are on membrance lipid peroxidation, and then SP and Pro contents increased and thendecreased, the activities of SOD, POD and APX reached the highest at the9th day, theactivity of CAT reached the highest at the6th day. It showed that the antioxidant system oftwo Sabina was activated under low temperature stress. It plays an important role in theformation of plant freezing tolerance.As differences between two species are concerned, RECand MDA contents in the leaves of Sabina przewalskii are lower than that of Sabina chinensis,contents of Pro and the activities of SOD, POD and APX in the leaves of Sabina przewalskiiare higher than that of Sabina chinensis, it indicated that Sabina przewalskii has morestronger ability to maintain the relative stability and structural integrity of the cell membranesystem.Under low temperature stress, certain concentrations of ABA could reduce theaccumulation of MDA, increase the contents of Pro, weak the effect of low temperature stresson SOD, POD, CAT and APX. It indicated that ABA can maintain the stability of membranesystem and increase the contents of osmotic regulators and activities of antioxidant enzymesenhance freezing tolerance of plant. Because most of the indicators reached a peak at the9thday, so a comprehensive assessment of index at the9th day was conducted, the resultsshowed that the best ABA concentration was found to be20mg/L for Sabina przewalskii and30mg/L for Sabina chinensis. Under low temperature stress, certain concentrations of SA could reduce theaccumulation of MDA, increase the contents of Pro, weak the effect of low temperature stresson SOD, POD, CAT, APX and GR. It indicated that SA can maintain the stability ofmembrane system and increase the contents of osmotic regulators and activities of antioxidantenzymes, enhance freezing tolerance of plant.Because most of the indicators reached a peak atthe6th day,so a comprehensive assessment of index at the6th day was conducted, the resultsshowed that the best SA concentration was found to be200mg/L for Sabina chinensis and30mg/L for Sabina przewalskii.In summary, spraying with certain concentration of exogenous hormone ABA or SA canreduce the content of REC and MDA in the leaves of Sabina under low temperature stress in acertain extent; can adjust osmotic substance and antioxidant enzyme activity, so as to reducethe damage caused by the low temperature stress, to improve freezing tolerance of Sabina.Under the pretreatment of certain concentrations of ABA or SA, Sabina przewalskii showedstronger cold resistance than Sabina chinensis. |
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