...a little on regeneration or switching back to veg after bloom has been in process, this is quoted from, "The Marijuana Grower's Handbook," by Ed Rosenthal (2006):
After the marijuana plant has ripened and the flowers have reached full maturity, it still responds to changes in its environment. Plants can be regenerated and can yield a second, third and possibly even more harvests. In it's natural environment, marijuana flowers in the fall, and then dies as the environment becomes hospitable and the numbers of daylight hours decrease. However, if the day length increases, the plant soon begins to revert from flowering to vegetative growth. At first, the plant produces single fingered leaves, the 3 and 5 fingered leaves. Within a few weeks the plants grow at the rapid vegetative rate. There are several advantages to regenerating marijuana plants rather than starting from seed. The plant has been harvested and its qualities and potency are known. The plant has already built its infrastructure. Its root system and main stem are already grown so that it takes less energy and time for the plant to produce new vegetative growth. A regenerated plant produces the same amount of vegetative growth in 45 days that takes a plant started from seed 75 days. To regenerate a plant , some leaves and bud material are left on the stem as the plant is harvested. The stem may be left at nearly its full length, or cut back to only a few inches from the ground. The more stem with leaf material left on the plant, the faster it regenerates, as new growth developes at the sites of the remaining leaf material. The plant starts flowering in response to a change in the light cycle.To stop the flowering process, the light cycle is turned back to a long day period. The plant reacts as if it had lived through the winter and renews growth as if it were spring. Within 7 - 10 days new non-flowering growth is apparent. Marijuana seems to react fastest to the change in light cycle when the light is kept on continually during the changeover period. After it has indicated new growth, the light cycle may be adjusted to the normal garden lighting cycle.