Karrikins – effect on plants, interaction with other growth regulators, and potential use in horticulture

Karrikins are a group of chemicals found in plant-derived smoke  from burning plant material. Till now, scientists concentrated on their effect on seed germination in plants sensitive to smoke. However, there are reports on the effect of karrikins on physiology and morphology in plants which do not occur in fire areas and are not naturally treated by smoke. These chemicals positively affect the biometric parameters of the in vitro cultured plants. Recently,  their effect on germination rate of pollen  in several species has been confirmed. They interact with plant growth regulators  enhancing their effects, for example using them together with auxins, cytokinins, gibberellins, abscisic acid or ethylene. This paper contains  a review of present research  on karrikins and proposes  perspectives of further investigations, as well as  application of these chemicals in horticultural production as a new group of plant growth regulators.