SOD and POD isozymes and proteins in the leaves of Euonymus radicans ‘Emorald & Gold' during the cold acclimation

A comparative observation was carried out on the changes of superoxide dismutase(SOD),peroxidase(POD) isozyme bands and total proteins in the leaves of Euonymus radicans ‘Emorald & Gold' during the cold acclimation,and the relationship between their variations and the plant cold resistance was discussed.The types of SOD in the seedling leaves were first distinguished.Resultsshowed that the SOD isozyme did not increase or decrease in band number,but the intensities of some bands increased,among which Cu-ZnSOD changed more obviously than FeSOD.POD isozyme had not only the enhancement of band intensity but also the appearance of a new weak isozyme band.The intensities of SOD and POD isozyme bands increased continuously with the prolongation of cold acclimation duration and culminated then declined to the control levels. So it was suggested that the adaptability to low temperatures caused by changes of isozymes during the cold acclimation might be one of the major reasons for enhancing the cold-resistance of plants.Four new acid proteins,A,E,F and G,with molecular weights of 18.7,19.5,15.7 and 18 kD caused by the cold acclimation still existed in the leaves of de-acclimated seedlings,whose contents decreased little,and they were considered to be antifreeze-proteins correlative to the antifreeze ability of acclimated seedlings under a series of freezing temperatures.It was also found that the contents of most proteins in the leaves of acclimated seedlings increased compared with unacclimated seedlings,among which the contents of alkaline proteins B(17.7 kD) and C(15.8 kD) as well as acid protein(15.5 kD) increased obviously.The contents of these 3 proteins in the leaves of de-acclimated seedlings all dropped to near the control levels and it was also suggested that the changes of proteins B,C and D might be correlated to the changes in the metabolic pathways of plants at low temperatures.