| Casuarina equisetifolia is a useful evergreen and fast-growing tree wildly introduced and cultivated in tropical and subtropical regions of the coastal loose sand. A lot of predecessors have carried many in-depth researches for plant physiology adapting to adversity. However, Casuarinas’adaptability in the face of adversity research is needed to further explore. In view of the poverty of tall tree species in Zhejiang coastal shelterbelt construction and the present situation of coastal ecological environment worsening, screening strong resistance Casuarinas’superior clones of the Zhejiang coastal forestry ecological construction has important theoretical significance and practical value. In order to explore the adversity physiological response mechanism, the writer selected several variations of C. equisetifolia from Yuhuan, Taizhou, Zhejiang Dalu islands as experimental materials, numbering B1, B2, B3, B4, R5, R6, G7and analyzed the chlorophyll fluorescence characteristics and the plant physiological indicators.This paper is written to provide some practical and theoretical basis for northward domesticated screening of Casuarina equisetifolia’s excellent type in Zhejiang.i The results showed that each variation had displayed different adaptabilities under low temperature stress in the natural. R5showed the strongest cold resistance with its greatest actual photochemistry quantum yield for PS II which indicated the most powerful photosynthesis efficiency. Fv/Fm of G7dropped most with the relatively weakest photosynthetic efficiency and cold resistance, as for cold resistance of the rest5variations was moderate. The qN of each variation had gotten different degrees of increase under the low temperature stress, which reacted diversities of the photosynthetic mechanisms for low temperature resistance damage,ii All variations’tendency of relative chlorophyll content (SPAD readings) in the measurement time was substantially consistent, which showed the first decline after rising trend. Comparing with other variations, B2and B3showed the higher relative chlorophyll content while R5and R6showed lower one. There are obvious diurnal change with photosynthetically active radiation and air temperature changes between the actual photochemistry quantum yield for PS Ⅱ, minimal fluorescence(Fo), Fv/Fm and qN of7variations of C. equisetifolia. In addition, G7has got a more notable diurnal change. Redskins got relatively small diurnal variations, with its stable physiological conditions. R5received least affects by light suppression, with its fastest capabilities of recovery, while G7got the greatest inhibitory effect of the light, with its slowest recovery capabilities. Besides, other variation types like B1, B2. B3, B4, and R6are at a moderate level. iii Consider with the diurnal variations and the results of cold resistance test, R5got the strongest superiority, while G7got the worst stress resistance. Other variation types like B1, B2, B3. B4and R6relatively stand a moderate level. Therefore the author excluded G7, and selected the best cold resistance R5and relatively high cold resistance B1for further salt resistance test. In the different treatments NaCl concentrations, the activity of SOD with the larger content of MDA in B1was higher than R5. while the POD activity and CAT activity in R5were higher than B1, which means B1got more hurt than R5cause the content of O2-in B1’s leaves increased more than R5’s. Analyzed by the total results from activities of antioxidant enzymes, the content of MDA and salt damage degree of injury, R5showed the stronger salt tolerance than B1. |
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