Studies On Leaf Structure Development And Glycometabolism Of Glycyrrhiza Under Different Water Gradients

In this paper,Glycyrrhiza uralensis seedlings were used as materials,and artificial control water was used to simulate soil drought habitat under pot culture conditions.Morphological characteristics and leaf ultrastructure of Glycyrrhiza uralensis seedlings under different water stress levels were observed.At the same time,photo synthetic performance and carbohydrate metabolism characteristics of leaves were measured.The main results are as follows:(1)Under normal water supply conditions(75%),the leaves of plants are bright green,with luxuriant leaves,spreading branches and robust growth;Under mild drought stress(60%),the leaves of plants remained fresh and vigorous.Under moderate drought stress(45%),leaf yellowing and wilting and branches drooping appeared.Under severe drought stress(30%),the plants appeared dry,with yellow edges curling,dry and necrotic branches and severe sagging.With the increase of drought degree,the root of licorice root is strong,root hair increases,stem and leaf atrophy and yellow,the ratio of aboveground to underground parts decreases.The increase of drought degree makes the licorice plant gradually lose water and wilt,the biomass of licorice will be transferred from the above part to the underground part,and the root will gradually grow to adapt to the dry environment.(2)With the aggravation of drought stress,the electrolyte permeability and MDA content of glycyrrhizae leaves showed a trend of gradually increasing,indicating that drought stress caused the normal physiological function of the cytoplasmic membrane to be disturbed.(3)Stomatal density and number of glands in the lower epidermis of leaves of licorice root were higher than those in the upper epidermis.Stomatal opening ratio and stomatal opening width of upper epidermis were higher than that of lower epidermis.With the increase of drought stress,stomatal density,stomatal opening ratio and stomatal opening width decreased gradually,while the number of glands increased with the increase of drought stress.The stomata of glycyrrhizae were slightly closed under moderate drought stress,while the stomata of glycyrrhizae were gradually closed under severe drought stress.It can be seen that the morphological structure of glycyrrhizae leaves will change with the change of habitat,which is an active way for plants to adapt to the environment.Moreover,this active adaptation to the drought-stressed habitat can not only improve the drought resistance of plants,but also reduce the damage they suffer in the drought environment.(4)With the increase of drought stress,Pn,Tr,and Gs in the leaves of glycyrrhizae seedlings all showed a trend of first increasing and then decreasing,reaching the maximum under mild drought stress.However,Ci increases gradually and reaches its maximum under severe drought stress.The chlorophyll content in the leaves of glycyrrhizae seedlings is reduced,which is a series of physiological responses of glycyrrhizae by reducing the chlorophyll content in the leaves and changing the photosynthetic characteristics to avoid the injury caused by drought stress.This indicated that glycyrrhiza root had certain drought resistance,and the photosynthetic capacity of glycyrrhiza root was reduced under severe drought conditions,and the factors limiting the photosynthetic capacity of glycyrrhiza root seedlings were caused by non-stomatal factors.(5)With the increase of drought stress,the soluble sugar,soluble protein and free proline in the leaves of glycyrrhizae seedlings all showed a gradually increasing trend,indicating that glycyrrhizae has a certain osmotic regulation ability under drought stress.By accumulating osmotic regulating substances,the water absorption and retention of cells were improved.(6)The content of sucrose,glucose and fructose in the leaves of glycyrrhiza uralensis was the highest in light drought stress.The content of sucrose in the three sugars was the highest,indicating that the leaves of glycyrrhizae were mainly sucrose accumulation.SPS had higher activity and promoted the synthesis of sucrose in leaf.SS-activity was much higher than SS+activity under various water conditions,indicating that the SS decomposition direction of glycyrrhiza leaf played a major role.The accumulation of glycyrrhiza leaf sugar was negatively correlated with the activity of NI and AI in leaves.NI activity was much higher than AI activity under various water conditions.The changes of starch phosphorylase activity in leaves of glycyrrhizae showed a decreasing trend,which was negatively correlated with the content of starch.(7)Under normal water control,sucrose was positively correlated with starch phosphorylase,while starch was negatively correlated with NI.Under mild drought stress,glucose was negatively correlated with SPS and positively correlated with starch phosphorylase.Fructose had extremely negative correlation with SPS and starch phosphorylase,and the correlation coefficient was-1.000.Starch was negatively correlated with SS-and positively correlated with AI and NI.Sucrose was positively correlated with AI under moderate drought stress.Fructose was positively correlated with SPS.Starch was positively correlated with SS-and negatively correlated with starch phosphorylase.Under severe drought stress,glucose and SS-were positively correlated.Fructose was negatively correlated with starch phosphorylase.Starch showed an extremely positive correlation with SS+and an extremely positive correlation with NI,with a correlation coefficient of 1.000.