Effects, Mechanisms And Application Foundation Of Soil Moisture On The Growth And Chemical Compositions Of Salvia Miltiorrhiza Bge.

Salvia miltiorrhiza Bge.(Danshen), as one of the important traditional Chinese medicines, has significant clinical medicinal values and effects in the treatment of cardiovascular diseases and diabetes. Previous studies in our laboratory showed that the active ingredient, salvianolic acid B (SaB), is a stress-induced post-harvest-drying product; in the fresh roots its content is minimal. In this study,cultivation experiments under different soil drought were constructed to further testify this conclusion. Secondly, our lab discovered that both fresh and dried Salvia contain large amounts of stachyose, its content of which positively correlated to the level of salvianolic acids (SAs). This result suggests that SAs might transform from stachyose, but still a further experiment is need to verify whether stachyose accumulation during the cultivation process can determine the SaB content in dried Salvia. Thirdly, some literatures reported that drought stress is conducive to the accumulation of sugars as well as SAs, which contradicts with our previous studies. Finally, the physiological response mechanism in drought stress of this plant is blank; the influence of drought stress on the growth and accumulation of active ingredient remains unclear. We carried out the present study,and obtained the following conditions:Soil moisture conditions have a significant impact on Salvia root biomass and stachyose content. Before the start of the drought,the Salvia biomass of three experimental groups showed that:medium moisture group> high moisture group> low moisture group;unlike other plants, salvia has accumulated a large amount of stachyose. the salvia biomass of three experimental groups showed that:high moisture group> medium moisture group> low moisture group.In the high moisture group, the lower soil moisture is, in the medium moisture group, when the soil moisture continues to decrease, the salvia biomass increase first and then decrease; in the low moisture group, when the soil moisture decreased, the salvia biomass would decrease. As to biomass, the modest reduction in soil moisture can promote the biomass transference of salvia from aboveground to underground and can promote the accumulation of biomass. Over reduction of soil moisture can do harm to the growth of salvia, and can also affects the stress mechanism of biomass transference, resulting in biomass continued to decline. As soil moisture content decreased, stachyose content of three experimental groups continued to decrease.This result differs from other literature that stachyose only accmulate in the case of anti-stress.Fresh Salvia roots cultivated under different water conditions contain relative higher tanshinones content, but only those cultivated under extreme drought stress (soil water potential <30%) can we detect SaB (<1%), but with no other phenolic acids detected. The SAs content of all the dried samples increased significantly, among which SaB content reached 4.2%, and tanshinones content increased by more than 30%. The contents of SaB and SAs in the drying roots showed a significant negative correlation with soil water potential during planting, meaning that during the cultivation process, the lower the soil moisture content, the higher the SAs content in dried root. Moderate drought stress during cultivation process is conductive to the production of SAs in the medicine. This conclusion is consistent with the literature.The contents of SaB and SAs in the dryed roots showed a significant negative correlation with the stachyose content in the fresh samples. Namely, the higher soil moisture content is, the more stachyose the roots contains,and the less SAs content in the dried root. This result indicates that the stachyose content in Salvia does not directly impact on SAs content in the dried root, which is inconsistent with the results we expected.The esponse mechanism of Salvia towards drought stress:As the drought deepened, a large number of reactive oxygen species (ROS) are produced. In the three experimental groups, soluble protein and MDA contained in salvia continued to increase, indicating the injury of drought stress on the salvia root stress continued to deepen.Among three experimental groups, the deeper the drought stress, the higher the SOD, POD and CAT activity. However, different enzymes function differently at different times:SOD activity rose the fastest in high moisture group; POD activity in high and medium moisture group rose faster than that in low moisture group; CAT activity rose the fastest in low moisture group. This result shows that as the first antioxidant defender, SOD can quickly respond to external stress in early drought stage, converting the superoxide anion into H2O2 and O2. Subsequently, in order to clear anti-oxidation product of SOD, H2O2, POD and CAT functions in turn by combining with H2O2 to reduce ROS content.In high and medium moisture group, total phenolic content of the salvia root decreased with the reduction of soil moisture. Salvia’s anti-oxidant capacity, such as scavenging DPPH and superoxide anion radicals, inhibiting lipid peroxidation continued to reduced accordingly. In extreme low moisture group(soil water potential <30%), accompanied by the production of SaB, SAs content and three antioxidant capacity increased sharply.In high and medium moisture groups with low non-enzymatic antioxidant content (early, middle drought stage), The activity of SOD, POD rose rapidly and functioned mainly to scavenge ROS; In low moisture group (late drought stage), antioxidant content functioned mainly to scavenge ROS, the effect of enzymatic system was relatively weakened.The two antioxidant defenders, coordinating and complementing each other, can defend drought stress in common.All the achievement mentioned above has not reported yet. They have some theoretical significance and application value in the study of salvia active ingredient accumulation and drought resistance mechanism.