Ok great,your here,i was just getting ready to pm you,from your links earlier in the thread you've obviously been researching this also,heve you read anything about using Gibberellic Acid or have you tried using it,this is becomming pretty interesting.
Btw,i have been trying to digest the info in your link all evening.
Yep, alongside the auxins IAA and NAA, Gibberellins are among the most popular and studied hormones/regulators.
Gibberellins are directly related to the abscisic acid group of phytohormones, as is the auxin group. IAA (and IBA) are in the auxin group. There are others. Have a look at this table:
Plant Hormones
The abscisic acid group is so named as it was first found in high concentrations in freshly fallen (abscissed) leaves/fruits. Abbreviated as ABA, it is primarily a growth inhibitor. The displacement of ABA is associated with increase in Gibberelin levels, prompting renewed growth or the triggering of another stage. For instance, ABA is part of the seed dormancy mechanism that allows seed to overwinter and not sprout during a warm winter period and part of the mechanism that prevents pre-mature flowering. Seeds have a lot of ABA, the levels drop triggering germination, then after the seedling is ready the levels drop again triggering vegetative growth, etc.
So, what is gibberelin? Gibberelins are a class of hormone that figure prominently in the seed germination mechanism as well as regulating the growth of internode cells in relation to light intensity. It is gibberelin that causes plants to stretch under low intensity light. Etiolated plants grown in near-darkness have gibberelin levels off the charts. Thus, supplementation with gibberelin can boost germination and can increase internode growth and bud/fruit size, but will stretch the plant by increasing internode distance.
Meanwhile, auxins in conjunction with other hormones (whose production it helps to regulate) control rooting, cell growth, and fruiting. IAA and NAA are the most often seen auxins. IBA (aka I-3-BA) is also very common. There are other less frequently seen forms of auxin, but I've found much less reliable information on them, some seem to be trademarked synthetic versions of the above. From what I've assimilated, IBA (or IAA) is to be preferred over NAA. IAA and IBA are naturally occurring in the plant, where as NAA is a synthetic auxin. For some stages of growth, like budding/ripening, NAA is an inhibitor rather than an activator (as is the case with many of these hormones.) Here's a snippet on synthetic auxins. Note the last part: not all auxins are something that you'd want in your marijuana garden!
Synthetic auxins, like naphthalene acetic acid, of NAA, are used extensively to promote root formation on stem and leaf cuttings. Gardeners often spray auxins on tomato plants to increase the number of fruits on each plant. When NAA is sprayed on young fruits of apple and olive trees, some of the fruits drop off so that the remaining fruits grow larger. When NAA is sprayed directly on maturing fruits, such as apples, pears and citrus fruits, several weeks before they are ready to be picked; NAA prevents the fruits from dropping off the trees before they are mature. The fact that auxins can have opposite effects, causing fruit to drop or preventing fruit from dropping, illustrates an important point. The effects of a hormone on a plant often depend on the stage of the plant's development. NAA is used to prevent the undesirable sprouting of stems from the base of ornamental trees. As previously discussed, stems contain a lateral bud at the base of each leaf. IN many stems, these buds fail to sprout as long as the plant's shoot tip is still intact. The inhibition of lateral buds by the presence of the shoot tip is called apical dominance. If the shoot tip of a plant is removed, the lateral buds begin to grow. If IAA or NAA is applied to the cut tip of the stem, the lateral buds remain dormant. This adaptation is manipulated to cultivate beautiful ornamental trees. NAA is used commercially to prevent buds from sprouting on potatoes during storage.
Another important synthetic auxin is 2,4-D, which is an herbicide, or weed killer. It selectively kills dicots, such as dandelions and pigweed, without injuring monocots, such as lawn grasses and cereal crops. Given our major dependence on cereals for food; 2,4-D has been of great value to agriculture. A mixture of 2, 4-D and another auxin, called Agent Orange, was used to destroy foliage in the jungles of Vietnam. A non-auxin contaminant in Agent Orange has caused severe health problems in many people who were exposed to it.
Cytokinins, another group and a word which may be familiar from seaweed/kelp product marketing, synergize with auxins, and also help to counteract apical (top) dominance by mediating the distribution of auxins and so encourage branching and lateral growth. They also slow the senescence (aging) of tissues.
Ethylene, conversely, inhibits leaf growth and encourages stem growth as well as speeding senescence and abscission of tissue--therefore, it is associated with the early vertical growth of seedlings, as well as the ripening of flowers and fruit (potentially continuing to the point of spoilage.) Ethylene also seems to be related to stem thickening, and in germination seedlings that encounter an obstacle in rising to the surface of the soil have an elevated ethylene level allowing them to thicken and exert more force, as well as helping them to counteract geotropism and 'go around' the obstacle. Plants caused to develop thicker stems by exposure to wind also have elevated ethylene levels (I would conjecture that this is why too strong a fan on your plants leads to leaf drop on lower growth--too much ethylene at the base of the plant in response to air turbulence.) In commercial fruit growning, often the production of ethylene, and so the ripening of tissues, is suppressed before the product is shipped closer to market at which point ethylene gas is introduced to cause ripening.
There are some other minor groupings of hormones that are either thought to serve auxillary functions (such as physiological signaling) or which are thought to have functions similar to those above but are not yet widely studied or well understood.
This is a decent place to start for a big picture, if the stuff I posted yesterday is too thick to make sense of:
Plant hormone - Wikipedia, the free encyclopedia
Incidentally, if you like this kind of stuff I can't recommend this book highly enough:
Amazon.com: Botany for Gardeners: Brian Capon: Books
Botany for Gardeners - Google Book Search
