Research On The Parasitic Mechanism Of Orobanche Cumana Wallr

The ripe seeds of Orobanche Cumana Wallr need a after-ripening for a period of time after their abscission, after being precultured for a certain time, the seeds which have been finished after-ripening can germinate only under induction of sunflower root exudates and other exogenous signal material, and then grow out haustorium which can pierce into the roots of sunflower to draw nutrient substance and water form sunflower plant, and then parasitic relation is set up. The earliest period of sunflower broomrape emergence is squaring period of sunflower, when most of the sunflowers are in flower, a large number of sunflower broomrapes has been emerged, but sunflower broomrapes are never been found emergence when sunflowers are in their seedling period. At present, the study of Orobanche Cumana Wallr home and aboard mainly focus on its biological characteristics, damage and control, however, so far, there are no researches on germination mechanism of Orobanche Cumana Wallr.This article wish to gather sunflower root exudates at seedling period and squaring period by the method of Hydroponic collect method, according to the research thinking of Bio-assay guiding separation, the separation and identification of seed germination irritant was guided by seed germination trials of Orobanche Cumana Wallr, and finally identified the sort of seed germination irritant, made sure the specific emergence period. Results are as follows:the compound type compositions of sunflower root exudates in the two periods are roughly the same, just different at the chemical composition and relative content of some compounds, and sunflower root exudates are constantly accumulated with sunflower growing, at the same time, some compounds are transformed or degraded.1. Both the sunflower root exudates at seeding period and squaring period can induce the germination of Orobanche Cumana Wallr, it is to say, sunflower root can exudate seed germination irritant of Orobanche Cumana Wallr both at seeding period and squaring period. At the same time, concentration of germination stimulus at squaring period is significantly higher than seedling period.2. There is Dehydrocostus lactone in sunflower root exudates, which can induce the germination of Orobanche Cumana Wallr.3. With the concentration of Dehydrocostus lactone rising, low concentration can promote seed germination, but high concentration will inhibit seed germination.4. Orobanche Cumana Wallr, a Orobanchaceae Orobanche holoparasitic herbaceous plant, has strong host specificity, mainly infect Sunflower. After infected by Orobanche Cumana Wallr, the Sunflowers grow slowly, stalks are low and thin; flower discs are thin and small and abortive grain increase; ability of resisting other plant diseases and insect pests descend; yield and quality also reduce substantially, flower discs affected seriously wither or die entirely, causing sunflowers result in. Because the emergence period of Orobanche Cumana Wallr are irregular,they can germinate from from budding to mature of sunflower. Besides, before Orobanche Cumana Wallr come out the ground, they already finished parasitism and damaged sunflower seriously. Therefore, chemical and biological control, methods widely used now all can not effectively control the damage of Orobanche Cumana Wallr, the most effective way is lessening the quantity of Orobanche Cumana Wallr seeds in soil to the greatest extent.