| This article studies the physiological and biochemical characteristics and isozymebands of POD of oilseed rape，one of the cold-tolerant plant. Then sift out the index ofcold tolerance, and finally, the model of a comprehensive evaluation ofcold-resistance had been established. Then explores cold resistance mechanism ofwinter oilseed rape in great depth, the main of it are as follows:1. Enzyme activities (SOD, CAT and POD) and the content of malondialdehyde(MDA) were measured; the peroxidase isozymes were studied. The results showedthat, in mild conditions, compared to the Brassica napus, Brassica campestris hashigher antioxidant enzyme activity and a lower level of lipid peroxidation. It indicatedthat Brassica campestris has strong stress resistance; especially peroxidase activityaverage was10times stronger than Brassica napus.67bands were found by PODisozyme analysis, and Brassica campestris and Brassica napus has its characteristicbands, there are also differences in the bands pattern and color intensity in differentvarieties. In Brassica campestris Largo、Prisma Hei and Prisma Huang, its p4enzymeband are consistent with Brassica napus, indicating that there is a close geneticrelationship between these materials and Brassica napus.2. As semi-lethal temperature as the reference index, the experiment analysis indexof cold resistance, relate to the physiology and biochemistry of the oilseed rape leaves,anatomical characteristic of it and so on, then screens out several reliable indexclosely related to cold-resistance to establish the multiple regression model of aevaluation of cold-resistance: Y=﹣18.362－0.034X1＋0.512X2－6.086X3＋0.14X4＋0.008X5－0.001X6(Y-semi-lethal temperature; X1-5~0℃POD; X2-0~-5℃CAT;X3-palisade-spongy ratio; X4-palisade tissue thickness;X5-leaf thickness;X6-poresize). It indicated that the multiple regression model is highly reliable by thesignificant detection of regression equation, the back-substitution check and thefractionation method combine with cold-resistance.3. For rapeseed roots of four different cold hardiness under continuously cool treatment (4℃24h,0℃24h,-3℃24h,-6℃24h,-9℃24h,-15℃24h,-21℃24h) inthe low temperature test box, testing the antioxidant enzymes activity (POD and CAT)and the POD isozymes electrophoresis showed that the activities of POD and CAT，inrapeseed root of the strong cold hardiness，had small changes at the early cooling time,and then increased continuously; however，the weak hardiness varieties, the activitiesof POD and CAT have had great changes in the early cooling time, and then keptconstantly. The results showed that the root cells of weak hardiness rapeseed frozencompletely in late cooling time, while the strong keep the cells in a solution statethrough a mechanism to avoid cells freezing. It stated that the key that strong coldhardiness rapeseed can winter safely was that avoiding freezing intracellularly and thelower freezing temperature of its cells is, the stronger the cold hardiness of them is.Weak cold hardiness rapeseed cannot winter safely because of the lethal damageproduced by intracellular freezing. In addition, there may be highly active antifreezeproteins in strong cold hardiness roots.4. The experiment also examines the antifreeze activities of apoplast which itobtained from the leaves and roots of the strong cold-resistance winter rape (Longyou6) by cold-induced treatment. The crude extract of apoplast shows obvious Activitiesto modify ice morphology and restrain recrystallization as seen through the lightmicroscope. It indicates that the antifreeze proteins exist in the crude extracts. Theprotein from apoplast was directly separated by SDS-PAGE gel electrophoresis andidentified a variety of protein of which the function remains unclear by massspectrometry binding MALDI-TOF/TOF. And some kinds of them are consistent withantifreeze protein of winter rye which is reported. |
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