I am preflowering under a 400W HPS right now. I have to leave the plants alone for a couple days over Christmas. Many preflowers are visible on the plants, but no sex is definite yet. How long does it take (on average) before the the balls rupture if the plant is male? I'll attatch a picture of a plant below. This plant is about 14" tall just to let you know. It's the furthest along in sexing.
Plants will take approx 14 days to show sex after turning the lights back to 12/12. Once a male "flowers" it will only be a couple of days before it will start to release pollen. good luck