Who met the lighting standards for seedlings of coniferous and deciduous trees / shrubs. Throw the link, please. Or for mature trees.
Yes, there are no such rules.
The normal light mode for plant seedlings is considered to be 10-14 hours of light day. You can increase it, a long artificial daylight hours will not harm.
If you mean exactly the level of illumination, then this is about 8 thousand lux. The most important thing is to choose the right color spectrum (blue, red) and not to dry the plants, be sure to consider the distance from the lighting device to the plant, it should not noticeably heat up.