Growing tomatoes

[lilbuddypizza]

I left my grow lights on overnight by accident will this effect the plants in anyway? They were on for about 20hrs +/- 30mins. Theres something else that confused me. When I got the setup I asked the guy how long I was supposed to leave them on for. He said 16 on, 6 off. What about those other 2 hours. Did he say it wrong or is it supposed to be a cycling at different times thing?

Late answer, but---
From what I understand, tomato plants grow more from soil warmth than sun (but of course they need sun).

[matermark]

I think they made a simple mistake. I  usually start them under lights for anywhere from 12-16 hours on, the rest off. I think I set my timer for 12 or 14.

Plants need an off period, this is when they grow. There was a study done about 50 years ago about which on/off length is best, I will try to find the pic if I didn't post it yet.

Here it is:(http://mysite.verizon.net/~korney19/301.jpg)