| In recent years, the rot of leaves always occurs when it is infected by fungi, such as Sclerotourm, and now becomes a popular problem for plant growth; and more evidence indicates that oxalic acid, a simple secondary metabolite of plant cell, plays a pivotal role in this process of fungi-plant interaction. In this study, oxalic acid was used as an abiotic elicitor for treatment of Psammosilene tunicoides suspension cells, and then the physiol-biochemical responses and changes in saponin content of cells were investigated, which would help to understand the mechanisms of resistance of plant cells against pathogen, as well as understanding of the responses of secondary metabolism to environmental stimulation.Through modulation of treatment time and concentration of exogenous oxalic acid, together with condition of illumination, the responses of suspension cells in the parameters of cell viability, permeability of plasmalemma, pH value of media, activities of peroxidase (POD) and catalase (CAT), lignifications, and saponin content to oxalic acid stimulation were examined; in addition, the role of ion channels in the process of oxalic acid-cells of P. tunicoides interaction was studied.The results are as follows:1. The concentration of oxalic acid was more than 5 mmol/L, the slight damage to suspension cells was observed, however, up to 20 mmol/L, most of the cells treated by oxalic acid were collapsed. Hence,5 mmol/L was the top concentration for the subsequent experiments.2. The activities of POD and CAT and cell vitality in cells provoked by oxalate acid treatment increased with oxalate concentration, and reached its maximum at concentration of 0.5 mmol/L, then declined gradually with the further elevation of oxalate concentration. The POD activity was confirmed to increase with time of oxalate treatment and reached its maximum after 16-20 h at 0.1 mmol/L, and then declined gradually. Meanwhile, an increase in CAT activity was also observed with time of oxalate treatment and reached its maximum after 12-16 h at 0.1 mmol/L, and then returned to its rest status gradually.3. When the concentration of oxalic acid was more than 0.5 mmol/L, lignin deposition within the cell wall increased with oxalate acid concentration, and the responses of cells to oxalic acid-induced stress grew strong, and the aging symptoms of cells were observed due to oxalic acid application. The degree of lignification of cells treated by 0.5 mmol/L became higher than that by 0.1 mmol/L. Through comparison of lignification with POD activity modulation by oxalic acid, it’s found that a close relationship between lignification and change in POD activity by oxalic acid existed in this process.4. pH value of media declined upon exogenous oxalic acid treatment, and it was not suitable for suspension cell growth when oxalic acid concentration was over 0.4 mmol/L.Comparison of cell treated by 0.5 mmol/L oxalate with control, the pH value of the former declined more than that of the latter.5. In addition, the oxalate-stimulated POD activity was inhibited significantly by three chemicals, including EGTA (a chelator of calcium ion), Tetraethylammonium chloride Minimum (TEA, inhibitor of potassium ion channel) and 4-Acetamido-4’isothiocyanate-2,2’ stilbenedisulfonic acid disodium salt hydrate (SITS, inhibitor of chloride ion channel).6. Under illumination, the oxalic acid-imposed stress to P. tunicoides suspension cells was relieved compared with that of darkness, which suggested the role of illumination in the process of oxalic acid-led stress.7. The accumulation of saponins of P. tunicoides suspension cells could be enhanced through interaction of oxalic acid with suspension cells, however, the concentration of oxalic acid was a key parameter and limited to less than 0.5 mmol/L on stream, in addition, the treatment time and pH of media must be taken into consideration,otherwise, severe aging or death of suspension cells would occur, not conducive to study and ultimately affected the yield of saponin and led to increase in production cost. |
PDF Full Text Request