| Isatis indigotica Fort.is a biennial herb of the Isatis genus,Cruciferae family.Its dry root is a kind of Traditional Chinese Medicine(TCM),named Banlangeng or ISATIDIS RADIX,which has the effect of clearing heat and detoxifying,cooling blood and stopping bleeding.Its dried leaf also is a kind of TCM,named Daqingye or ISATIDIS FOLIUM,which has the same function as its root but clearing blood spotting.Both of the two parts are belong to bulk medicinal materials in TCM.At present,there are relatively few studies on the cultivation of the herb in China,and the cultivation conditions need to be optimized.In this study,the herb's seeds provided by Jilin Tongrentang were used as experimental materials.The germination of I.indigotica seeds was carried out by using PEG6000 to simulate drought stress and NaCl to simulate salt stress,and the effects of germination on its seeds were studied.Growth index,photosynthetic characteristics and physiological indexes of the herb under drought stress.To investigate the adaptation mechanism of I.indigotica plant to drought stress during growth,and to provide a theoretical basis for the cultivation and management of the plant in Changchun City.The research results are as follows:(1)Mild drought stress(PEG concentration 3%)can increase the germination rate and germination potential of I.indigotica seeds,and mild salt stress(NaCl concentration 20mmo/L and 40mmol/L)can promote the growth of the herb's radicle,hypocotyls and seedlings.When the I.indigotica seeds are subjected to drought stress,the seed germination peak will be advanced one to two days.With the increase of drought stress and salt stress,the germination potential,germination rate,germination index and daily average germination number of I.indigotica seeds were gradually increased.(2)The aerial part of the plant is more susceptible to drought stress than the underground part.Moderate drought stress can increase the root-shoot ratio of it and increase the root yield.The overall growth and development of the plant was significantly inhibited by drought stress,and with the increase of stress,the plant height,main root length,leaf length,leaf width,root thickness and growth of it decreased significantly.Under drought stress,the water content in the aerial part slowly decreased,the water content in the underground part increased gradually,and the plant distributed more growth amount to the root system,resulting in a gradual increase in root-shoot ratio.(3)Under suitable water(85% relative water content in the field)and mild drought stress(65% relative water content in the field),stomatal limitation is the main factor for the decrease of net photosynthetic rate drop(Pn)in I.indigotica plant;and non-stomatal limitation is the main factor for the decrease of its Pn under moderate stress(45% relative water content)and severe drought(25% relative water content in the field);drought stress leads to a decrease in transpiration rate(Tr)and the Tr peak moving forward.As the degree of drought stress intensifies,I.indigotica plant can significantly reduce the Pn,Tr and stomatal conductance(Gs)of the leaves in response to drought and water shortage,thus improving the water use efficiency(WUE)under drought conditions,narrowing the gap with WUE in the case of adequate water supply.(4)Under the arid environment,the nitrogen metabolism in the aboveground part of I.indigotica plant is stronger than the sugar metabolism in it.The sugar metabolism in the underground is stronger than the nitrogen metabolism in the infiltration.The cell membrane of the plant under severe drought stress is suffering from irreversible damage.The chlorophyll content of the plant decreased gradually with the degree of drought stress,while the activities of antioxidant enzyme systems consisting of superoxide dismutase(SOD),peroxidase(POD)and catalase(CAT)increased significantly,and the osmotic adjustment molecules such as malondialdehyde(MDA)content,soluble sugar content and soluble protein content generally showed an upward trend under drought stress. |
PDF Full Text Request