What are Plant Growth Regulators (PGRs)?

Plant growth regulators are naturally occurring, hormone-like chemicals specific to plants. The function of PGRs is to mimic or inhibit the expression of a plant’s normal growth hormones during its life-cycle. This includes when the plant begins to germinate when its fruits ripen and drop, as well as the length, width, and shape of the plant’s roots, leaves, and stems.

Why Do Cannabis Farmers Use Them?

For marijuana, PGRs are mostly used to alter the appearance of the buds, increase yields, or make the plant size more uniform for indoor growing. Some growers also claim that PGRs add to the overall health of the plant, making it stronger and more resistant to disease. However, much of the problems with PGRs, especially synthetic ones, come from less than honest growers looking to increase profitability at the expense of quality and consumer health. This is especially noticeable with how PGR manipulated buds appear after curing.

PGRs increase yields by cellular expansion through signal transduction pathways. When growth stimulating genes are activated, cells begin to grow and increase in size. … This expanding outward pressure from the extra water inside the plants cell is one cause for the added weight observed in crops grown with PGRs.

PGRs have been used in agriculture and landscaping for nearly a century. Depending on the PGR, their use ranges from increasing the number of apples in an orchard to slowing the growth of grass in a golf course so that can be mowed less often.

Some of the Most Common PGRs:

Paclobutrazol

This PGR retards a plant cell’s ability to elongate. When used on cannabis, this means that the cells pack much tighter and denser on the flower. While this bud may look like a higher value product, Paclobutrazol actually hinders the development of key terpenes in the cannabis plant. This has a much greater effect on quality than just how the flower tastes and smells.

Daminozide

Also known as Alar, Daminozide is used by growers to maximize bud yields. It does this by minimizing the growth of stems and leaves so that the plant can put more resources into flowering. However, like Paclobutrazol, this PGR decreases the production of terpenes, as well as cannabinoids like CBD, CBN, and THC. Basically, it severely restricts resin production in the plant overall, meaning fewer trichomes.

Chlormequat Chloride

Chlormequat Chloride actually slows down plant growth in certain areas, which in turn helps to encourage flowering. Adding it to plant also can make their size much shorter and more uniform, which makes growing plants indoors a lot easier.

Are PGRs Bad for You?

Yes. Exposure to high doses of synthetic PGRs can be very dangerous to people’s health in both the short and long term. In the late 1980’s, the EPA issued a recall of Alar (Daminozide) for food uses as testing found that it could be classified as a carcinogen in high doses. It’s been banned from human consumption since 1989 and has led to several agricultural recalls. Many synthetic PGRs have been similarly banned as further tests have been done.

The EPA also has concerns that Paclobutrazol might cause liver damage, and may also affect fertility in both men and women. While Chlormequat Chloride has not yet been shown to be hazardous to people’s health, testing is still being done.

How to Avoid Consuming Marijuana Grown with PGRs

pgr vs no-pgrThe best way to avoid synthetic plant growth regulators is to ask your friendly neighborhood budtender. They should have some idea of their grower’s reputation. You can also call the producers themselves and request information.

If your budtender is uncertain or the producer uncommunicative, there are certain things to watch out for when buying your flower. The first is incredibly dense buds. Of course, dense buds can also be a mark of a master grower, which is why you should make sure they’re also dusted with trichomes.

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