Is a Plant Growth Regulator (PGR) Safe?
So what is a PGR?
Paclobutrazol (PBZ) is a plant growth retardant (usually used in the vegetative cycle onwards) and works via being a giberellic acid (GA3) antagonist. For the science buffs out there, it’s a competitive inhibitor with irreversible binding to the iron core of the three enzymes involved at different stages in the synthesis of gibberelins. However, the takeaway message for the average person is that it stops the plant functioning in a normal manner by shutting down the following enzymatic pathways:
- Terpene synthases
- Cytochrome P450 mono-oxygenases (P450s)
- 2-oxoglutarate–dependent dioxygenases
Daminozide AKA alar is usually used in the flower mix and is another antagonist, but to abscisic acid instead of GA3. There aren’t a lot of visual effects caused by alar except for odd colouration of the fruit due to excess amounts of phytyl (a precursor to chlorophyll) accumulating.
Chlormequat Chloride is the final PGR common in flowering mixtures.
This is a plant growth regulator that inhibits the synthesis of GA3 in a similar way to PBZ, and therefore many of the effects caused by it are similar to PBZ’s and similarly, it causes a myriad of problems much like PBZ (though likely through different mechanisms).
We recommend to many of our customers that a PGR isn't the right way to go. It might increase the time but producing a decent fruit will lead to better quality and repeat sales.