WASHINGTON — The U.S. Supreme Court will begin oral arguments today in the case of Vernon Hugh Bowman v. Monsanto Company, et al.

Mr. Bowman, a 75-year-old soybean farmer from Indiana, bought and used soybeans that happened to contain genes pioneered by Monsanto that conferred protection against the widely used Roundup herbicide. Monsanto has rules in place that require farmers to buy fresh “Roundup Ready” seeds each year from the company to ensure a financial return on the company’s investment in the protective genes.

The lawsuit has important ramifications for manufacturers of bioengineered seeds and for the farmers who use them. It also is viewed as having broader patent implications for manufacturers well outside the realm of agriculture, such as the software and nanotechnology industries.

At stake is whether patent protection for the creator of a bioengineered seed — in this case Monsanto — extends beyond the first generation of the seed’s use. The question is, was Mr. Bowman within his legal rights when he purchased and planted seeds that happened to contain “Roundup ready” genes from a vendor other than Monsanto?

Monsanto has licensing agreements that require farmers to buy bioengineered seed with protection against the herbicide Roundup each year they plant. Farmers are forbidden to buy seeds that may have the protective gene but were cultivated and then sold outside Monsanto’s legally protected system. Lower federal courts have ruled in favor of Monsanto.

Monsanto argues that its patent protection extends beyond the first-generation seeds while Mr. Bowman has contended that the patent is essentially exhausted when the plants mature from the initial first-generation seeds and produce a new generation of seeds. Farmers, in Mr. Bowman’s view, should be free to purchase their soybean seeds from any source they wish. (As it happens, the “Roundup ready” gene is likely to be found in most soybean seeds available because of its wide use.)

Monsanto has argued that, if Mr. Bowman wins the case, farmers will become de facto competitors with Monsanto, able to plant their soybean fields with bioengineered seeds obtained anywhere and denying the company a reasonable return on the hundreds of millions of dollars it took  Monsanto to develop “Roundup ready” soybeans.