1 Viewed from Centre of Eternity 615.552.5747 -+- The Merry Pranksters from Menlo Park -+- 10.1990.01.01.27 Marijuana Grower's Handbook - part 27 of 33 by pH Imbalance "Advanced Flowering" from Marijuana Grower's Handbook [Indoor/Greenhouse Edition] Ed Rosenthal [pH:This chapter has 21 pages of charts and diagrams that I did not enter, that are very informative and highly useful. If you want them, buy the book.] In Part 25 (Flowering), marijuana's photoperiod response was described. Most varieties of cannabis flower in response to changes in the light cycle. This is a foolproof method for a plant to determine when to flower when it is adapted to a particular location. Every year the ratio of dark to light remains the same at a particular date. Scientists think that plants measure the number of hours of darkness by producing a hormone, tentatively named florigen. This hormone has not actually been discovered. The theory is that when the level of this hormone reaches a critical level, the plant goes into its reproductive mode. Through simple experimentation, we know some interesting things about this plant response. It is a localized response by the plant. This was discovered by shading one branch of a plant but leaving the rest of it without a daily dark period. Only the branch that was shaded flowered. (This is a viable technique to use to sex plants). Researchers think thatthe hormone is produced by the plant continuously. However, it is destroyed or metabolized by an enzyme or hormone which is produced only in the presence of light. Under natural conditions, the critical level builds up only with the onset of long nights in the autumn. When the dark cycle is interrupted by light, even for a few minutes or less, the florigen is destroyed by the plant and the plant starts the buildup to the critical level over again. The response to different light cycles is a graduated one. Plants that initiate flowering at one light/darkness routine flower more heavily when the amount of darkness is increased. This response is more pronounced on plants originating from a higher latitude where the light cycle changes more. Chrysanthemums are also long night-flowering plants, and their growth patterns have been studied extensively for use by the greenhouse industry. Researchers found that the largest flowers with the highest total weight were grown when the dark cycle routine was provided each night. When the plants were shaded 6 nights a week, there was a slight diminution of flower size and total weight. With each additional unshaded night, flower size and weight dropped. [pH:Now, you are probably thinking "That doesn't make one damned bit of sense!" and you are correct. I don't know what Ed was thinking in this instance, so I won't bother to correct THIS error, but if one reads it, if the plants are shaded for 6 nights a week, they get smaller. If you "unshade" them, they also get smaller. You're screwed either way, apparently.] Cannabis is one of the most widespread plants. It is naturalized everywhere from the equator to the arctic. (Private cannabis gardens have also been documented as being grown by scientists stationed at outposts in the Antarctic - it's not illegal there since no country has sovreignty). The plant has developed many variations on the photoperiod response to adjust to different climactic and latitudinal conditions. Female plants from equatorial or sub-equatorial zones such as Colombia, southern Mexico, central Africa, and south India are absolute photo-determinate (APD). These plants are acclimated to latitudes in which there is little variation in the light cycle throughout the year. As long as the dark period falls below a minimum trigger period, the plant remains in the vegetative growth cycle. This can go on for years under continuous light conditions. When the dark period lengthens to a trigger point, the plant changes its growth pattern to sexual development. If the dark period falls below the trigger level when the plants are flowering, the plants easily revert back to vegetative growth. APD plants are good candidates to flower and regenerate. Since they respond to the light cycle in a relatively simple way, irregular or interrupted cycles alter growth significantly. Buds are smaller, leafier, fluffier, looser, and may run. They look a bit like low-light flowers. Flower size can be increased by allowing the plants to ripen fully, then placing them in a continuous light regimen for a few days. Flowering is triggers again and the plants produce new clusters of flowers. [pH:Perhaps Ed didn't write this chapter, because it is repeating too much stuff he's already said, and besides: That isn't going to increase the flower SIZE, it will increase the amount harvested.] Some cannabis varieties are "relative photoperiod determinate" (RPD). These plants have a trigger that they respond to under normal growing conditions, but when they receive an unusual light regimen, they respond to the change in the light conditions in unusual ways. For example, an early flowering indica normally triggers at 10 hours of darkness, but if it is grown under continuous light and then the darkness cycle is increased to 8 hours, the plant triggers. Once these plants are triggered, the light cycle has less affect upon them than upon the APDs. The developing flowers are not as sensitive to occasional interruption of the darkness cycle. RPD varieties include the mid- and high-range latitude-adapted plants including Moroccans and southern Africans, early indicas, commercial hemp and hybrids developed for early harvest (September or earlier). RPD varieties are harder to manipulate using the light cycle. Plants placed into flowering do not revert to vegetative growth as easily as APD varieties. [pH:Perhaps I'm in a bad mood, but does he have to keep fucking repeating himself? This is annoying as HELL!] The plants are harder to regenerate. Light stress promotes hermaphroditism in these varieties. They are harder to clone; they take longer and have a lower success rate. Most males and some extreme northern varieties including the ruderalis strains fall into a third category which is not photosensitive at all. Both age and development seem to play a role in determining when these plants flower. For example, a Hungarian ruderalis developed flowers under continuous light after 8 weeks. Most varieties of males indicate under continuous light after 3-9 months. Thais and some equatorial sativa males are exceptions and will not flower until the dark period is increased. Under 18 hours of light, males indicate sooner than under continuous light. Cold may hasten sexual expression but not flower development of some northern varieties. Some varieties, especially indicas, respond to unnatural light cycles by showing photo-period response disorder. Genetic females turn hermaphroditic when exposed to long dark periods during early growth. (818-752-2572) XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX XX XX XX Altered States XX XX XX XXXXXXXXXXXXXXXXX | XXXXXXXXXXXXXXXXX XX | XX XXXXXXXXXXXXXXXXX | XXXXXXXXXXXXXXXXX X V X X One of those Crazy boards tha