Effects Of SO₂ On Some Physiological And Biochemical Characteristics Of Mulberry And On The Related Enzymes Of Silkworm Glutathione (GSH) Metabolism

Potted mulberry seedlings as materials were placed in enclosed volume-fixed box made of synthetic glass and added with SO₂ with different concentrations, and the main physiologic and biochemical properties were studied. The SO₂ poisoning is serious problem to silkworm cocoon Production in main sericultural area of China.In order to find out meehanism of fluoride toxicology to silkworms.the glutathione and some correlate enzymes in hemolymph of the fluoride poisoned silkworm larvae wereassayed,and the effects of fluoride on glutathione metabolism of Poisoning silkworm were diseussed. Main results are as follows:while the concentration of SO₂ rose, necrotic areas appeared on the leaves and high level SO₂ led to large necrotic area and even wilting; content of sulphur in leaves increased while concentration of SO₂ rose;the activity of CAT increased with SO₂ level in prior stage and decreased on high SO₂ level (50 mg/m³)in later stage; MDA content increased gradually; SOD activity decreased obviously. Under relatively low stress(10,30mg/m³), POD activity increased evidently while under relatively high stress(50mg/m³) it declined. As SO₂ stress enhanced, chlorophyll content and net photosynthetic rate of mulberry leaves increased while soluble protein content and proline content decreased. Activity of protective enzyme was inhibited by SO₂ stress which led to more serious injury, and necrotic areas appeared on leaves while photosynthetic rate declined, and all those changes had negative influences on the growth and development of mulberry.The experiment showed, the content of glutathione(GSH) decreased from the first day To the fourth day,while increase from the fourth day to the sixth day in normal larvae.After feeding with SO₂ solution,the content was degressive,the higher concerntration of SO₂ Solution,the lower of the glutathione content, the mean content of GSH of male silkworm was 49.3μmol/L and that of female silkworm was 41.0μmol/L.The GST activity ascend from the first day to the third day,while descend from the third day.After feeding with SO₂ solution,GST activity increased.Theγ-GT activity ascend from the first day to the fourth day ,while flown from the fourth day to the seventhday, the mean activity of GST in male silkworm was 21.80U/L and that of female silkworm was 24.98U/L.After feeding with SO₂ Solution,γ-GT activity increased obviously, the higher dose of SO₂ Solution,the higher of its activity.The glutathione synthetases activity always increased from the first day to the sixthday,and after feeding with SO₂ Solution,the activity increased, the mean activity of GSH in male silkworm was 0.31U/L and that of female silkworm was 0.33U/L.The GSH-Px activity increased from the first day to the third day.while decreased from the third day to the sixthday,and after feeding with SO₂ Solution,GSH-Px activity increased, the mean activity of GSH-Px in male silkworm was 17.16U/L and that of female silkworm was 17.34U/L.The content of oxygen free radical increased from the first day to the third day, while descend from the third day to the sixthday.The content increased after feeding with SO₂ Solution.while the levels of oxygen free radical decreased after GSH treatment in hemolymph of the fluoride poisoned silkworm, the mean content of oxygen free radical of male silkworm was 10.31μmol/L and that of female silkworm was 9.42μmol/L..The content of malondialdehyde increased from the first day to the third day ,after that it presented stable, the mean content of MDA of male silkworm was 0.56μmol/3L and that of female silkworm was 0.53μmol/3L.The content of malondialdehyde increased after feeding with SO₂ Solution ,while the levels decreased after GSH treatment in hemolymph of the fluoride poisoned silkworm.The oxygen free radical and malondialdehyde also showed that GSH had an effect of remitting fluoride poison to silkworm. Keywords: SO₂; Mulberry; Stress Physiology; Enzyme activity; MDA; Proline; Soluble Protein; Silkworm; glutathione; oxygen free radical...