Plant Growth Regulators

By Jasper Shotts

Plant Growth Regulators are a broad group of plant hormones, that influence positively, or negatively, the growth rate of plants and/or fruit maturation rates. The variety of plant growth regulators include auxins, cytokines, gibberellins, ethylene and abscisic acid. Plant growth regulators interactions with humans is varied; some are not toxic, while others are considered carcinogenic. Plant growth regulators are regulated as pesticides. Commonly used PGR’s include gibberellin, indole-3-butaric acid, mepiquat chloride, trin exapec ethyl, 1-naphthylacetic acid, maleic hydrazine, paclobutrazol, daminozide, uniconazole, ethephon and prohexidione calcium. A few of these are approved for use in food or other products for human consumption; however, the majority are not and the warning ‘for ornamental plants only” is on the label. It is illegal, in America, to use some of these PGR’s in plants that humans will consume, including cannabis. The two main PGR’s that get used in cannabis that humans should not consume is daminozide and paclobutrazol. Daminozide and paclobutrazol have been found in hydroponic products across the nation and are considered carcinogenic or possibly carcinogenic by regulatory agencies.

Auxins and Gibberellins are plant growth regulators that stimulate plant growth. Gibberellins improve seed germination rate and encourage rapid growth. The rapid growth encourages large spacing between nodes or branches and improves air flow under the canopy. Auxins stimulate growth and is used by plants during phototropism. Phototropism is when the plant orients towards the light. The most popular auxin utilized is indole-4-butyric acid. Indole-4-butyric acid is the active ingredient in some cloning gels that are used to clone weed plants.

Paclobutrazol and Daminozide are plant growth regulators still used in the greenhouse industry. Neither is approved for use in consumable items such as food or cannabis. Paclobutrazol products have never applied for food use so the EPA has not examined human toxicity. However, a study done on rats indicated liver damage occurred from exposure. Daminozide is a known human carcinogen and is on the 2B list along with welding fumes and engine exhaust. The EPA declared in 1998 that death or permanent injury may result from short exposure to small quantities. These substances have been found in some densening products and why they carry the label ‘for ornamental use only’.

Ethylene, abscisic acid and phenolics are plant growth regulators. Ethylene affects ripening of fruit. Ethylene gets used on tomatoes often. Tomatoes are treated in shipment and/or storage to give them the ripe red look you see at the stores. Phenolics are used to delay abscission. Abscisic acid is present in seeds and prevents germination.

Plant growth regulators play an important role in the agriculture industry. Plant growth regulators achieve a variety of positive effects on the plant. However, some have negative effects in humans and should only be used in orchids, roses or other ornamental plants that will never be consumed. Check the labels and research any product to find out what is in it before using, and never use things that say for ‘ornamental use’ on your plants because you are poisoning your nugs.

Article Produced by Green Magi Labs Inc.