Studies On Induced Resistance In Cucumber With Hypocrellin A

The induced resistance of plants, also called acquired physiological immunity or systemanic acquired resistance, is a defense against the microbes in the plant after treated by the biological or non-biological factors. Many biological factors, such as fungi, bacteria, virus or their metabolic intermediates; physical factors, such as ultraviolet, temperature pressure; and chemical factors, e.g. salicylic acid and tryptophan, can induce the resistant reactions in plant against the virus, bacteria and fungi.The photosensitivity of HA, an excellent natural pigment, can not only be applied in curing many critical dermatosis, but also in inhibiting cancer and HIV. Recent studies show that HA in micellar solution, both in light and in dark, has a good inhibition in intruding effects towards a variety of microbes. Up to now, however, no report on the role of HA in the induced resistance of plant is available.The effects of inducible resistance were discussed by employing HA, which was extracted from Shiraia bambusicola and used as an example of PQDs, to treat the experimental plant strains, and through the research on the changes of activity of four enzymes, including polyphenoloxidase, phenylalanine ammonia lyase, peroxidase and superoxide dismutase, which related to the plant resistant reactions, and use Pseudomonas syringae pv. Lachrymans, which is harmful to the vegetable grow in glasshouses in recent years as sample bacteria.The results were as follows:1. Acid-alkaline precipatation combined with Soxhlet extraction was used to extract and purify HA from Shiraia bambusicola with acetone as the extraction solvent. The content of HA determined was 81% by spectrophotometer. The advantage of this method is dramatically saving reagents and time, simplifying the procedures in comparison with the conventional chromatography methods. It can be applied in extracting HA from the natural products or ferment products. In addition, HA crude sample extracted by this means can meet the need of producing green agrochemicals.2. The activities of four resistance-related enzymes contained in cucumber leaves can be enhanced after treatment by solution of HA with TritonX-100. The time needed to reach peak value of the activity of POD is the least and the span is the largest. Time difference between four enzymes for reaching peak value of their activity may be related to the timeof their effects in plants. Also, they may be related to the velocity of inducing and expressing different gene in plants.3. The enzyme activity of different inducible dosage, the stages of the plant disease and the resistant effect were investigated, the results indicate that the enzyme activities have positive relationship with all the aspects, which are corresponding with many references. The activities of PPO and POD under the treatment of 10ppm after 7- 14 days are higher than the other groups and the effect of resistant to the disease is 90.48%. We speculate that PPO and POD can catalyze polymerization and oxidation of phenol, thus can inhibit the growth of the microbes and have better activity than others.4. HA can generate much reactive oxygen under the sunlight. When there are many reductants, e.g. cysteine and vitamin C, the quantum yield of ROS can be improved greatly. ROS is indispensable during the course of anti-infection against the microbes in the plant. For instance, ROS is involved in the hypersensitive responses, the lignification of the cell wall, the linkage of proteins and the inducible expression of many genes. Therefore, it is predicted that ROS may be crucial during the inducible resistant to some diseases in the cucumber strain .treated by the TritonX-100 containing HA.