SO₂ And CH₂O Stress On The Physiological Metabolism Of Taxus Chinensis Var.Mairei

With the rapid economic development, the rapid increase of noxious gas pollution, the sulfur dioxide is one of the most common and harmful gas, the usage of Plants with high absorbency to certain air pollutant in atmospheric pollution control has become a new and rapidly Strengthened subject, of which the study on the stress of SO2 was a focus. Meanwhile, in recent years, new materials with artificial lumbers have been used more and more widely. This makes CH2O become one of the main indoor air Pollutants. Using both Physiological methods and chemical methods to remove CH2O in Indoor environment have some limitations and oxidants can make the secondary Pollutions.In order to explore the resistance mechanism of Taxus chinensis var.mairei to sulfa dioxide (SO2) and formaldehyde (CH2O) stress, the physiological responses and anti-oxidation enzymes were evaluated under the exposure of the various SO2 and CH2O concentrations. In this experiment, one-year-old potted seedlings were placed in an enclosed fumigation chamber, single-gas SO2 and single-gas CH2O concentration was respectively set as 0 mg/m3,5 mg/m3,10 mg/m3,20 mg/m3,40 mg/m3 for 1,3,5,7 days.other treatment is mixture-gas of SO2 and CH2O treatment, set as 0mg/m3+0mg/m3,2.5mg/m3+2.5mg/m3, 5mg/m3+5mg/m3,10mg/m3+10mg/m3mg/m3,20mg/m3+20mg/m3 for 1,3,5,7 days.Under the stress of single-gas SO2 treatment, The results indicated that the membrane permeability, the contents of malondialdehyde (MDA), proline and Cys, while the contents of chlorophyll a and b were decreased with the increase of SO2 concentrations and periods. The results also showed that the injury symptoms in leaves were observed at 20 mg/m3 SO2 concentration after 5 days exposure. The activities of peroxidase (POD) and ascorbate peroxidase(APX) were induced at 5 mg/m3 SO2 stress, while those of superoxide dismutase (SOD) and GR were induced at 10 mg/m3 SO2.Under 40mg/m3SO2 stress, the activities of SOD、CAT and APX significantly decreased in comparison with those in control, while those of POD is still higher. Our data suggested that Taxus chinensis var.mairei can improve the resistance to SO2.stress through turning on own protection system under 10mg/m3SO2 stress.Under the stress of single-gas CH2O treatment, The results also showed that there is a significant decrease of chlorophyll a and b at C1 treatment over 1 day CH2O exposure, and chlorophyll a is injured more seriously than chlorophyll b. The content of malonaldehyde (MDA) and soluble sugar (SS) changed with the same tenancy in which they revealed a significant increase under all the CH2O treatments in comparison with control. The relative electric conductivity and the content of proline reached the maximum at the highest CH2O fumigation over 7 days. The activities of six free-radical-processing enzymes were evaluated under various CH2O exposures, and they exhibited different sensitivity to CH2O treatment. The activity of SOD increased significantly with the rising of CH2O concentration over 1,3, 5, and 7 days treatment in comparison with the control, while that of POD and PPO increased significantly only over 1,3, days treatment. Surprisingly, the activity of CAT dramatically declined nearly three-fold at all the four CH2O treatments during the whole experiment period in comparison with the control. SOD firstly catalyzes O2 to H2O2, and then POD and CAT, sequentially converts H2O2 to harmless O2 and H2O. This catalyzing sequence was supported by our data that SOD activity was activated more dramatically than POD and CAT under CH2O exposure. The activity of APX revealed a pronounced rise under all the four CH2O treatments, and continued to rise with the prolonged exposure time and reached the five-fold relative value at the C4 treatment over 7days exposure in comparison with the control. Compared with control, the activity of GR significantly increased at the C1 treatment and remained unchanged without statistically significant differences under the increasing CH2O exposure concentrations and periods. In combined with the phenotypic symptoms, our data suggested that Taxus chinensis var.mairei exhibits better resistance to the CH2O of low concentration exposure and can be used to decontaminate indoor CH2O air pollutants.Under the stress The mixture-gas of SO2 and CH2O treatment, the leaves damage than single-gas SO2 treatment is lighter, but more serious than single-gas CH2O treatment. All changes of physiological indexes showed that did not show the composite gas super position effect, Compared with the single gas stress, the leaves stocking hurt less. The results show that under the stress of a variety of gas stocking resistance performance is more obvious.The conclusion is that the single-gas CH2O treatment>the mixture-gas of SO2 and CH2O treatment>single-gas SO2 treatment.