Effects and Related Mechanisms of Allelopathy of Ambrosia trifida's Pollens on Corn Pollens, Stigmas, and Yield

Ambrosia trifida, a worldwide malignant invasive weed, can inhibit corn seed germination, seedling growth, and yield through allelopathy. However, it is unclear whether it can inhibit activities of corn pollens and stigmas and, thus, decrease corn yield through allelopathy. Here, we studied the allelopathic effects and related mechanisms of A. trifida's pollens on corn pollens, stigmas, and yield. The aqueous extract of A. trifida's pollens significantly inhibited activities of corn pollens and stigmas. Treating corn pollens and/or stigmas with A. trifida's pollens or their aqueous extract significantly decreased corn fruiting. Four allelochemicals were identified from A. trifida's pollens, which could significantly inhibit activities of corn pollens and stigmas, especially isoquercetin and quercetin. These compounds could interact with five key enzymes in the respiratory metabolism of corn, inhibiting the activities of these enzymes and, thus, respiratory metabolism. Our study provides a new pathway and mechanism by which invasive plants affect crop yield.