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甾醇是植物体内的重要次生物质,具有多种生物活性。为探明植物甾醇类物质对害虫的作用机理,采用叶碟饲喂法进行取食处理后研究了苍耳Xanthium sibiricum中分离纯化的甾醇类组分(甾醇A和甾醇B)对4龄菜青虫Pieris rapae的取食、酶活性以及中肠组织的影响。结果表明:苍耳甾醇类组分甾醇A和甾醇B能明显抑制菜青虫的取食,拒食中浓度AFC50分别为0.0229和0.0147mg/mL;同时,显著降低菜青虫中肠蛋白酶、淀粉酶和羧酸酯酶活性,其中,甾醇B的作用效果较强,处理后24h和36h,对蛋白酶活性抑制率分别为23.74%和58.59%,对中肠羧酸酯酶的活性抑制率分别为49.01%和83.03%;降低血淋巴蛋白质含量,诱导菜青虫血淋巴羧酸酯酶活性的提高;破坏昆虫中肠上皮组织,微杆模糊不清呈消融状,杯状细胞的杯腔基部微绒毛消失。这些结果说明苍耳甾醇类物质对菜青虫的取食抑制可能与对中肠消化酶活性的抑制以及对中肠上皮组织的破坏有关,植物甾醇组分的不同配比影响其对昆虫的作用效果。
Sterols are important secondary substances in plants and have a variety of biological activities. In order to investigate the action mechanism of plant sterols on pests, we studied the effect of sterol components (sterol A and sterol B) isolated from Xanthium sibiricum Pieris rapae feeding, enzyme activity and the impact of mid-gut tissue. The results showed that cocklebur sterol components sterol A and sterol B could obviously inhibit the feeding of Pieris rapae, with the concentrations of AFC50 of 0.0229 and 0.0147 mg / mL, respectively. At the same time, the intestinal protease, amylase and carboxylase The activity of sterol B was stronger, the inhibitory rates of protease activity were 23.74% and 58.59% at 24h and 36h after treatment respectively, and the inhibitory rates on carboxylesterase activity of midgut were 49.01% and 83.03% respectively. The content of hemolymph protein was decreased, the carboxylesterase activity of hemolymph of Pieris rapae was increased, the epithelial tissue of insect midgut was destroyed, the blurring of micro bar was ablated, and the microvilli disappeared at the base of goblet cells. These results suggest that the inhibition of feeding of salamantel to Pieris rapae may be related to the inhibition of midgut digestive enzyme activity and the destruction of midgut epithelial tissue. The different ratio of phytosterol component affects its effect on insects .