E.I. du Pont de Nemours & Co. and Langebio, the Mexico National Laboratory of Genomics for Biodiversity, have entered into a research collaboration to increase understanding of plant reproductive biology and genetic diversity, the organizations announced Tuesday. Under the agreement, DuPont subsidiary Pioneer Hi-Bred International Inc., which is based in Johnston, will work with Langebio on several projects to gain new insights into the biological and genetic mechanisms that control plant productivity. Specific terms of the agreement were not disclosed.