| Camellia hiemalis is an important shrub of winter florescence in eastern China. For evergreen and long period of blooming, it will be widely used in gardens. It is necessary to study physiology of cold resistance for selecting culture varieties and their extension to northern China, but few researches are found about this area. In this paper, with various treatments of low temperatures, the characteristics of physiologic and biochemical of C. sasanqua were determined in Camellia hiemalis 'ShiShi Gashira', which is a very common culture variety in used now. The results are as below:1. The relative Electric Conductivity (REC %) was regarded as the reliable physiological indication for tolerance to low temperature in leaves of C. hiemalis. In different levels of low temperature and treatment period, it was confirmed that the cell membrane of 'ShiShi Gashira'were injured under low temperature, and REC increases sharply. The leaves obviously frozen stiff after two hours storage with temperature below -10 in C. hiemalis . Meanwhile, the REC increased from 13% to 22%, and reached to 31% 24 hours later, and up to 35% after 48 hours. With the treatment of -20 , REC increased dramatically from 13% to 46% after 6 hours, and to 51% 24 hours later. It showed that the leakage of electrolyte in cell membrane gradually increased as the response of low temperature in C. hiemalis .2. REC increasing curves were described depended on the different levels of low temperature and treatment period. Following these REC curves and logistic equation, we calculated the LTso of C. hiemalis . The "S" shaped increasing curves of REC was found for the treatments storage longer than 6 hours with the temperature dropping. From the inflexion of "S" curve, we could calculate theof C. hiemalis 'ShiShi Gashira'. And we suggested -12.5 to -14 as the LT50 which considered as an important guideline of cold tolerance in C. hiemalis .3. Along with the storage in low temperature, the water contents decreased slowly in leaves of C. hiemalis. Meanwhile, the unmarked increase for concentrations of soluble sugar was found which indicated the thickness of cell liquid could enhance the cold resistance. For storage in -5 , the concentrations of soluble sugar in leaves changed slightly in first 4 days, but increased sharply 6 days later, and up to 90.02mg/100g at 8th day compared to the stared concentration as68.23mg/100g.4. There was no obvious relationship between the concentrations of free proline and low temperature in leaves of C. hiemalis. Stored at 0 , the free proline contents increase from 1.2 g/g to 2.2 g/g one day later, and reached 29.7 g/g in the second day, then dropped to 12.02 g/g 72 hours later. At -20 , it decreased from 6.1 g/g to 4.6 g/g one day later, but increased to 18.6 g/g in the second day. It needs further researches to explain.5. As the response of low temperature, the activity of enzymes about peroxidation of cell membrane showed different results. The activity of SOD gradually enhanced in the first 4 days, but decreased later. For example, at -10 the SOD activity for increases from 20.1 to 30.3 unit g-1 in first two days, and reached 45.0 unit g-1 at 4th day, but dropped to 32.1 unit g-1 6 days later, and continued down to 26.7 unit g-1 at 8th day. The CAT activity showed increase from 197 to 250 mgH2O2 g -1 min-1 in first 2-4 days at 0 storage in C. hiemalis, but decreased to 187.58 mgH2O2 g-1 min-1 at 6th day, and then increased dramatically to 359 mgH2O2 g-1 min-1 8 days later. Different results showed at the storage in -15 , the CAT activity dropped quickly from 289.4 to 138.9mgH2O2 g-1 min-1 after 2 days, but up to up to 205.83 mgH2O2 g-1 min-1 4 days later, and reached to 291.65 mgH2O2 g-1 min-1 at 6th day, then fell again as 202.1 mgH2O2 g-1 'min'1 at 8th day.Based on the discussions about the physiological and biochemical changes in leaves of C. hiemalis stressed on the low temperature, the suitable indicator for cold tolerance was suggested in the pa... |
PDF Full Text Request