Photosynthesis has two stages, one that occurs during the day, and the other that occurs during the night. Sixteen hours is a lot of daylight, I wouldn't push it any further.

I grow my seedlings with 16 hours per day of light, also useing a fan. I have never run my lights more than 16hrs, but i have run them less than 16hrs and the results wasn't as good! These seedling have been grown under lights with 16hr of light a day.

tobin34 - sorry I am not a pro and am new at growing daylilys from seed - but I was wondering if Lyle could let us know what that is he's growing the seedlings in and how he starts them and pots them up.
thanks

Thank you all for the input. I have grown many of my perennials indoors from seed and know they all have diferent lighting needs. I also understand how important it is to give the plants a certain period of darkness.

For Irish Rose Grower, I believe The seedlings are being grown in styrofoam with holes open to the bottom for watering purposes. Very clever and neat. That eliminates the need for many pots or cups. Must make transporting simpler and more cost effective.

Thanks again.....Tobin.