KN, having done high security indoor gardening in the past I can say that plants grow just fine under artifical lighting 1/5 as intensive as sunlight.
And I don't doubt that at all. But that goes against Josi's original premise of solar-only setup.
You literally cannot feed plants the further out you go in space, and we are talking about deep-space explorations, not just explorations within our solar system.
Sunlight is way more intense in outer space due to not being filtered through earth's atmosphere. I would guess that at Jupiter's orbit sunlight is less intense than at earth's surface, but not by much.
And plants require such filtering too. But even then, they will all die before you even hit Neptune.