Studies Of Melittin On Physiological Effects Of Zea Mays

Melittin, which is from Bee Venom, is one of the insect antimicrobial peptides withstrongest bactericidal effect. It can inhibit or kill not only medical pathogenic bacteria but alsopathogens in crops. Because of the characters of broad spectrum, quick effect and highperformance, melittin shows a great potential of advantages in agriculture. Zea mays L.seedlings had been selected as the experimental materials and the effect of high concentrationmelittin which was100-500times higher than5mg/L on some nutrition indexes andresistance indexes of Zea mays seedlings had been studied here. It hoped that the mechanismof melittin for plant cells could be found. At the same time, this study simulated the pesticidespraying methods (spraying1time,2times,3times) in agriculture to seek the optimalspraying method. The results shown that different concentration melittin (500mg/L,1000mg/L and1500mg/L) with different spraying methods could significantly improve thecontent of chlorophyll, soluble sugar and protein and five defensive system enzyme activitiesincluding POD, PPO, SOD, CAT and PAL. Melittin could also reduce membrane lipidper-oxidation MDA content. Spraying500mg/L melittin with1or2times could improvesignificantly the content of chlorophyll, and1time spraying method was batter than2or3times; Spraying1000mg/L melittin with three methods could increase the content of solublesugar; When spraying1time, three concentrations could significantly raise protein content.Moreover, three concentrations melittin could reduce MDA content when using melittin1time, while1500mg/L melittin with2or3times increased MDA content, which indicated thathigh concentration melittin with more times had some effects on plant cells; Overall, theeffects of melittin on five defensive system enzymes displayed that different concentrations ofmelittin with different spraying methods could heighten their activities during24h, likespraying1500mg/L melittin3times significantly enhanced POD activity after6h(104.1%);500mg/L melittin with2times improved PPO activity113.2%after72h,107.6%after120h;Using1500mg/L melittin with3times increased SOD activity73.99%; Spraying1000mg/Lmelittin with2times heightened CAT activity58.53%during24h; PAL activity showed thatall concentrations of melittin improved PAL activity after48h under spraying with1time,and500mg/L melittin increased PAL27.66%. It could be found that three spraying methodscould improve enzyme activities,1time was the optimal spraying method taking into accountthe easy operation and saving. And, there was no toxicity lethal effect to plant cells in thisstudy, which further proved that the action of melittin on plant cells was different from on pathogen cells. Melittin could start defensive system enzyme activities quickly and efficientlyand enhance the disease resistance of plants, which clarified toxic mechanism of melittin toplant cells and the disease-resistant mechanism finally and had important significance formelittin to be a biological pesticide.