Effect Of Epibrassinolide On Lipid Peroxidation And Osmoregulation Substances In Leaves Of Achyranthes Bidentata Subjected To Waterlogging Stress

Achyranthes bidentata Bl, an important traditional chinese herbals have many Medicinal attributes such as improving memory, regulating immunity, delaying caducity and preventing tumors. A. bidentata is widely grown in Northern China, and have the best quality when grown in parts of henan province. Unfortunately, A. bidentata seedlings often encounter waterlogging stress during its early growth stage. The aerobic respiration and photosynthesis of A. bidentata seedlings are frequently inhibited by waterlogging stress, therefore, both yield and medical value of achyranthes root decline due to the more consumption and less accumulation of organic matter. So, it is necessary to find a way to alleviate the photosynthesis inhibition caused by waterlogging damage.Recent researches indicate that Epibrassinolide(BR) has positive physiological effects on many crops under normal and adverse circumstances. Whether BR can help A. bidentata obtain higher output and quality under waterlogging stress, by means of enhancing the activities of antioxidant enzymes, increasing the content of osmoregulation substance and improving photosynthesis? There is no report about this up to now. Effects of BR on antioxidant metabolism, osmotic adjustment, membrane stability, chlorophyll fluorescence parameters in leaves and catalpol content in roots of A. bidentata subjected to waterlogging stress were studied by spraying BR solutions in different concentrations (0, 0.025,0.05,0.1 and 0.2 mg/L ) on the seedlings. The purpose of this experiment was to study the effects of BR on the water logging tolerance, yield and quality of A. bidentata. Main results are as follows. Firstly, the ability of A. bidentata removing active oxygen under waterlogging stress was enhanced by BR.Because SOD activity is mostly affected by substrate concentration, at early days of stress at different stages, the ability of SOD was enhanced with the content of O2- .But with the time prolonging, some enzyme protein started destructure, so the ability of SOD fell sharply. Affected by concentration of substrates, APX had the similar varying trends as SOD. Although spaying with BR didn't change the trends of SOD and APX, increase at first and then decrease, spaying BR had the higher activity of SOD and APX than B0, even if approached level of CK. At the same time, the decrease of CAT activity was well inhibited by BR. So the high ability of removing active oxygen was maintained in A. bidentata leaves under waterlogging stress, which reduced the accumulation of free radicals, released the damage to biomembrane system and retarded the membrane-lipid peroxidation. Therefore, the permeability of plasmic membrane diminished, cellular contents and ion leakage cut down.Secondly, the potential and efficiency of photosynthesis in the leaves of A. bidentata under waterlogging stress were increased by BRThylakoid membranes is the structural basis for chloroplast to absorb, impress and transform light energy. Photosynthetic pigment, the important component of thylakoid membranes, is the receptor of light energy. The content of pigment in the leaves is the key index reflecting the ability of photosynthesis. The changing of circumstance can lead to the changing of photosynthetic pigment content, and further lead to photosynthesis characters change. The research indicated that the chlorophyll in the leaves of A. bidentata degraded under waterlogging stress. But the chlorophyll synthesis was higher than chlorophyll degradation at the early stage of water logging srtess after spraying BR. The degradation of he chlorophyll spraying with BR began strong also with the time prolonging, but the scope of degradation was less than B0 all the time, which provided the some material guarantee to photosynthesis for the leaves of the A. bidentata under waterlogging stress. The experiment showed that the higher Fv/Fo, Fv/Fm,ФPSâ…¡and qP were maintained in leaves pretreated with BR under waterlogging stress. All of above illuminated that BR exerts somewhat protection on the leaves of A. bidentata under waterlogging stress by not only restraining chlorophyll degrade, but also promoting it synthesize, so the potential and efficiency of photosynthesis in the leaves of A. bidentata under waterlogging stress were enhanced, and the best concentration of BR was 0.05mg/L.Thirdly, the contents of hydrophilic material in the leaves of A. bidentata under waterlogging stress were increased by BR The accumulating of proline has the positive protection for the plant in adversity. The increasing of soluble sugar contents can reduce the osmotic potential of bioplasm and do benefit for absorbing water from the lower water-potential circumstance to maintain the normal metabolic activities in the plant. The results of this test showed that the accumulating of proline and soluble sugar was enhanced by spraying BR on the leaves, which had the good effects on osmotic adjustment and offered some guarantee to other physiological functions. The plant can directly be involved in the process of adapting the adversity by increasing the synthesis of soluble proteins in adversity conditions. Spraying BR on leaves played the role of promoting the proteins synthesis at the beginning of stress, and performed the function of controlling the degradation of them with the stress strengthening. The results illuminated that, under waterlogging stress, spraying BR on leaves of A. bidentata can maintain the content of proteins by promoting the new of them synthesis or controlling some of them degradation, which can increased the hydrophilicity of cell and indirectly improved the waterlogging-resistant ability of A. bidentata The concentration effects among the treatment were obvious, but 0.1mg/L was the best concentration.Fourthly, Eeffect of Epibrassinolide on Yield and Quality of Achyranthes bidentata Subjected to waterlodging StressWater logging can result in the electron leakage in the course of electron transportation, so overmuch free radical comes into being. But the activity of antioxidase depress during the waterlogging process, which make more free radical accumulate to attack membrane system of cells. So the chlorophyll begin to degrade, the absorbing and transferring of light energy are affected, which influenced the photosynthesis further. Accordingly, biosynthesis and metabolism are disordered, the yield and quality of crops are influenced also. The results of this test confirmed that spraying with BR on the leaves of A. bidentata could not only reduce the injury during the waterlogging process, but also the contents of osmoregulation substances were increased, which had an ability to compensate the adverse effect of water metabolism, so the adaptive mechanism in the A. bidentata could go well more to obtain high yield and quality. 0.1mg/L of BR had the distinct aftereffect.All the results obtained in the present study confirmed that the suitable concentration of BR could effectively induce the water-logging tolerance of A. bidentata because it could decrease the accumulation of O₂^- and H₂O₂ by enhancing the ability of SOD, APX and CAT and reduce the content of substance in membrane lipid peroxidation. So the stability of cell membrane system was protected, the degradation of chlorophyll was controlled, higher Fv/Fo, Fv/Fm,ФPSâ…¡and qP were maintained, and the more photosynthate was acquired. As a result, the output of A. bidentata root was increased and the quality of root was improved owing to the enhancement of drought tolerance and the harmonious metabolism.