Physiological Responses Of Lagerstroemia Indica To Sulfur Dioxide Stress And Polymorphism Of CpDNA In Lagerstroemia L.

In china, Lagerstroemia indica is one of the significant flowering trees in Summer. It has the superiors of longer florescence ,beautiful flowers and resistance to pollution. One of the previous study shows leaves of L. indica absorb some sulfur dioxide gas, but any other papers about physiological responses of L. indica to sulfur dioxide stress can not finded. In this study, two-year-old potted samples of L. indica were treated with different concentrations of sulfur dioxide gas in a closed fumigation equipment, the changes in activities of SOD, POD and CAT, membrane permeability, and contents of MDA, proline, soluble proteins, chlorophyll of them were measured. The results showed that L. indica resisted pollution. We also have studied the phylogenetic relationships within Lagerstroemia based on cpDNA trnG intron sequences,9 species(27 individuals)were analyzed.The results are as follows:1. After the matierals were exposed to sulfur dioxide gas at concentrations of 0-19.00 mg·m^-3 for 15 days, the membrane permeability, the contents of MDA and the proline of them increased, while soluble protein content increased and then decreased and the contents of chlorophyll-a,chlorophyll-b and total chlorophyll decreased with the increment of sulfur dioxide concentration compared with the control level.2. With the increase of SO₂ concentration, the SOD, POD, CAT activity on samples showed an upward trend. The increase of SOD and CAT activity are similar. The enzyme activity increased slowly when the samples been treated with the SO₂ concentration between 0 to 14.25 mg·m^-3,while it increased rapidly at the concentration of 19 mg·m^-3, meanwhile the SOD and CAT activity increased by 44.9% and 74.37% compared with the control. The POD activity growth trends are different with SOD and CAT, which increased by 46.04% under the concentration of 0 to14.25 mg·m^-3 compared with the control but it almost didn't increase at the concentration of 19 mg·m-3. The results indicated that the increasing of the three antioxidant enzymes can improve the resistance of L.indica to SO₂ and plays an important role in clearing the O₂^- and H₂O₂, and reducing the degree of membrane lipid peroxidation.3. The CTAB method in extracting DNA from dry leaves was modified and the PCR amplification reaction system for cpDNA trnG intron was set up. By decreasing the amount of dry leaves to 0.02g per 2ml centrifugal tube, repeating the purification step once and deleting the step of RNAse disgestion, high quality DNA was obtained and materials and time was saved.4. By analyzing the cpDNA trnG intron sequences, there are 17 variable sites,10 parsimony information sites(without outgroup). GC content is 28.5%, which is low. Sequences between the following paris: L.indica and L.guilingensis, L.limii and L .subcostata, L. speciosa and L .intermedia, L. balansae and L. villosa are same, which indicate that the relationships of these paris are very close. Intron sequences of eight L.indica varieties are exactly the same, too. So this fragment is unfitted to classify L.indica varieties.L.speciosa from Guangdong and Yunnan hasn't genetic differentiation.L.venusta has many variable sites. the maximum of Kimura-two parameter distance among L.venusta,L.indica and L.guilingensis is 0.017,.5. Using Cuphea hyssopifolia as outgroup,in the most parsimonious(MP) tree (length=82;CI=0.9634;RI=0.9625),there are four clades.The first clade include eight L.indica varieties, L.guilingensis,L.limii and L.subcostata. The second clade included L.siamica, L.villosa and L.balansae. The third clade was consiste of L.speciosa and L.intermedia. The fourth clade include only L.venusta. The genetic relationship of L.venusta with other species is the farthest, and it may be early differentiate from the other species of this genus.