Once an industrial-chemical titan, GMO seed giant Monsanto has rebranded itself as a “sustainable agriculture company.” Forget such classic post-war corporate atrocities as PCB and dioxin—the modern Monsanto “uses plant breeding and biotechnology to create seeds that grow into stronger, more resilient crops that require fewer resources,” as the company’s website has it.

That rhetoric may have to change, though, if Monsanto succeeds in buying its Swiss rival, pesticide giant Syngenta. On Friday, Syngenta’s board rejected a $45 billion takeover bid. But that’s hardly the end of the story. Tuesday afternoon, Syngenta’s share price was holding steady at a level about 20 percent higher than it was before Monsanto’s bid—an indication that investors consider an eventual deal quite possible. As The Wall Street Journal’s Helen Thomas put it, the Syngenta board’s initial rejection of Monsanto’s overture may just be a way of saying, “This deal makes sense, but Syngenta can hold out for more.”

The logic for the deal is simple: Syngenta is Monsanto’s perfect complement. Monsanto ranks as the globe’s largest purveyor of seeds (genetically modified and otherwise), alongside a relatively small chemical division (mainly devoted to the herbicide Roundup), which makes up just a third of its $15.8 billion in total sales.