I'm with Headgardner22 on this topic, I was always told that as soon as the shoot tip detects light it switches off root development in favour of leaf production. Other members on this site disagree and say that chitting sweetcorn seed is a popular method of germination and should not be discounted. I am OK with that so I experimented with various suppliers including open varieties and organic brought back from a trip to the U.S.A. I found that I had to watch seed chitted on damp paper like a hawk, in case it dried out/ rotted as not all seed is treated/ pick off rooted seed as some rooted early and burrowed roots into the paper.
By comparison, seed sown one to a three inch pot late April and planted out late May to mid June as and when the conditions were right provide me with enough cobs. From a packet of seed there will be loss, it only needs the best twentyfive plants laid out in a block five by five, fifteen inches apart. 'Golden Bantam Improved' and any of the UK 'Supersweet' varieties have been great and LOL late and early plantings managed to mature roughly at the same time; thanks to a neighbours kernel stripper they freeze well. As far as sweetcorn is concerned I don't faff, I save that for Squash, Cucumber, Melon and Parsnips where I have to.
The idea that the roots stop growing if the tip of it detects light is IMO not close to being correct. A very productive method of growing veg is to use air pruning pots, as soon as the roots get to the many holes, that root stops and sends out many more fibrous ones.
I also sow many trays of micro leaf veg and the seed is almost always uncovered after the first few seeds start shooting, leaving many more to shoot in the light, if the roots stopped growing straight away, I would have poor growth, which I don't.
I agree with Gandan, sowing only seeds that you are 100% certain are viable is not a faff, and a chitting a packet of seeds takes less time than filling up pots, watering and then sowing seed that will never grow.
Totty
Edited to take Totty's reply outside the quote.