棉铃虫的取食营养特点与棉花抗虫素分布的关系

通过研究棉花8个部位对棉铃虫Helicoverpa armzgera的营养效果和其所含次生物质类萜烯和单宁的浓度及在组织中的分布，揭示了棉铃虫取食营养特点与棉花次生化学的关系。棉铃虫取食顶尖、转移蛀食蕾铃的习性，与有关器官或组织对幼虫的营养效果密切相关，而营养效果主要取决于类萜烯和单宁的含量。棉花顶尖嫩叶中单宁浓度随着棉花的生长发育呈升高的趋势；类萜烯浓度在第四真叶期、第六真叶期和现蕾初期之间出现一个明显的底谷，而此期幼虫主要为害顶尖。蕾铃外层的苞叶、花萼、花瓣和铃皮，因次生物质含量高，不利于幼虫生长，相反内部的花粉、子房和铃心，次生物质含量低，营养效果好，顶尖嫩叶则介于其间。类萜烯存在于组织的色素腺内，分布集中；单宁则散布于组织中，偏多分布于组织外层。结果证实，昆虫在寄主植物上的取食方式是昆虫对寄主体内变动的次生化学的一种适应，它使昆虫付出尽少代价获得最适营养效果。

ON THE RELATIONSHIP BETWEEN LARVAL FEEDING BEHAVIOR OF COTTON BOLLWORM AND DISTRIBUTION OF HARMFUL ALLELOCHEMICALS IN COTTON

The nourishment of different parts of cotton plant, namely, the terminal leaf, bract, calyx, petal, anther, ovary, boll husk and boll heart, to cotton bollworm Helicoverpa armigera (Hubner) larvae and the distribution of terpenoid and tannin contents, the major secondary metabolites unfavorable to the larvae, in these cotton tissues were tested for exploring the relationship between feeding behavior of cotton bollworm larvae and the two kinds of allelochemicals in cotton. The results showed that the factthat the larvae preferred to feed on plant tip and bore into square and boll was closely related to the nutritive effect, mainly depended on the contents of terpenoids and tannins, of these organs on themselves. The tannin contents in terminal leaf gradually increased with the course of cotton's development, while there were significant drops ofterpenoid contents in terminal leaf in the 4th leaf, 6th leaf and early square stages, which were just the times the larvae damaged on cotton plant tip. The contents of secondary metabolites in outside parts of square and boll, such as bract, calyx, petal and boll husk, were higher than those in their inner parts, pollen, ovary and boll heart,etc. , and that in terminal leaf was intermediate. The terpenoids mainly presented in pigment glands, and tannins mainly scattered in the tissues of outer layer of cottonplants. It was indicated that certain feeding behavior of insect such as the feeding times and locations of cotton bollworm larvae is formed by its adaptability to the fluctuating contents of harmful secondary metabolites in host plant.