Not all chitosans or oligosaccharides derived from chitin activate the defence response of plants. Not all chitooligosaccharides derived from chitin are active. The chain of oligosaccharides acts in the same way as a key, and as such, it only fits specific locks, which can be only recognised by specific proteins (CERK1) of the plant.
It is scientifically proven that the chitooligosaccharides that are recognised by receptors, and are therefore able to activate a response, have a degree of polymerisation comprised between 5 and 14. Out of this range, the induction of defence responses in the plant is very poor or even non-existent.
The chitooligosaccharides contained in stemicol® have a molecular weight below 3000 Dalton and a degree of polymerisation between 5 and 18 monomer units, which guarantees a good activation of the defence responses.