FOR decades, the uninterrupted programming on PBS has been one of its most distinctive selling points to audiences and philanthropic and corporate supporters alike.

But those leisurely stretches of break-free programs could be going away.

PBS officials told member stations at its recent annual meeting in Orlando that beginning this fall, the Wednesday science series “Nature” and “Nova” would contain corporate and foundation sponsor spots, promotional messages and branding within four breaks inside the shows, instead of at the very beginning and end.

The longest period of uninterrupted programming, according to a plan shown to the programmers, would be just under 15 minutes, compared with the current 50 minutes or more. Based on what PBS learns in the fall, the new format would continue to be introduced night by night through the year, officials said.

Even before the plan became public last week, it was being intensely debated among PBS station executives and program producers. While many support testing the new model, others are worried about how viewers and the financial supporters will react, and if PBS can recover should they react badly.