Comparative Study On Physiological Characteristics Of Two Kinds Of Large And Medium-sized Evergreen Fern In Cold Area

The weather is dry and cold in Harbin in winter. The factor of impacting evergreen plants to overwinter is complex. The evergreen fern which to adapt the cold is little. In terms of evergreen fern which can hardiness and its mechanism is lack of systemic, this article through studies the change in protective enzyme system, photosynthetic characteristics, osmoregulation substance of Phyllitis japonica and Dryopteris crassirhizoma seasonally and the relationship between the cold hardiness and physiological characteristics, which can provide basic data for evergreen mechanism and the mechanism of cold resistance.The results showed that:(1)With the changing seasons, the variation trends of enzyme activity of Phyllitis japonica and Dryopteris crassirhizoma are similar. Dryopteris crassirhizoma in the process of changing seasons, the SOD activity reached highest in December, although between December and March SOD activity decline still higher than in other months, POD activity is reduced in January to march, and during November to January the CAT activity increased, but POD activity of Phyllitis japonica increased from November to January, that means although affected by cold stress, three kinds of protective enzyme coordinate with each other to make ferns has certain adaptability to low temperature stress. In terms of protective enzyme activity, to maintain the cell membrane integrity, ensure the safety of wintering important physiological reaction under the condition of low temperature freezing, protective enzyme activity of two kinds of evergreen fern leaf enhanced, antioxidant accumulation, leaf antioxidant system timely removal of oxygen free radicals to prevent membrane lipid peroxidation. But the differences between the different species, antioxidant system of Dryopteris crassirhizoma has more extensive adaptability strategy in frost resistance induction, Dryopteris crassirhizoma show the stronger frost resistance.(2) Two ferns in seasonal change into the cold season in November, its soluble sugar and soluble protein content of leaf were significantly increased, Increase amplitude of Phyllitis japonica is higher than Dryopteris crassirhizoma, which means the increase of soluble sugar content and soluble protein content of Phyllitis japonica has a more important role in the process of cold hardiness. With the rebound in the spring, the plant growth and recovery ability, soluble sugar content of Phyllitis japonica and Dryopteris crassirhizoma increased to supply the material for plant growth and thawing and recovery and ability. As the change of season, the change of MDA content was shown as “up-down” may be due to the initial exercise for its low temperature stage, two kinds of ferns formed certain fight cold ability.(3) Enter autumn early winter that is during September to November, chlorophyll content and chlorophyll a and chlorophyll b content of Phyllitis japonica and Dryopteris crassirhizoma and is reduced different degrees, that is to say two ferns have fight cold ability. And Dryopteris crassirhizoma's chlorophyll content is higher than Phyllitis japonica, chlorophyll content can be a reference index to judge plant cold hardiness, can see Dryopteris crassirhizoma can fight cold higher than Phyllitis japonica.