THE Role of plant substances in polymorphism of the aphid myzus persicae
1978
HARREWIJN, P.
In aphids polymorphism is a complex seasonal phenomenon influenced by a number of intrinsic and extrinsic factors. Polymorphism is connected to host alternation and to generation succession. In all cases studied, morph determination is regulated by physical factors and by social relationships such as population density. Apart from these factors, the host plant can play a dominating role in wing dimorphism of different species. There is also evidence that the condition of the host may influence the production of sexuparae. Host plant substances influencing morph determination in M. persicae can be divided into a number of classes: I. Nutrients per se, stimulating growth and reproduction. They have an indirect effect on wing production, as they influence population density (crowding effect). II. Factors affecting restlessness of the aphids. III. Factors acting as “tokens”, triggering the aphid brain to initiate the production of the apterous or alate morph. IV. Specific morph-active substances, which interfere with the response of the brain to environmental factors, such as crowding. V. Pseudo-crowding factors. They are introduced into the plant by the aphids and influence aphids at a different site on the plant. For each of these classes examples are given and their possible mode of action is discussed.
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