Smoke On The Water

Germination responses to smoke-water, KAR1 and glyceronitrile

Germination responses to smoke-water, KAR1 and glyceronitrile

Some plants live in envir­on­ments where fire is a fre­quent enemy to sur­vival. Unless you’re big enough to out­grow the risk of fire with tough bark like Sequoia, the obvi­ous answer is to lie dormant in the soil until the fire has passed, help­fully leav­ing lots of nice nutri­ents avail­able for ger­min­at­ing seeds. But if you’re bur­ied in the soil, you need to know when the time for ger­min­a­tion comes before you get out-competed by spe­cies which are quicker off the mark.

In 1990, de Lange and Boucher repor­ted the land­mark dis­cov­ery that aer­o­sol smoke and aqueous smoke-water could pro­mote the ger­min­a­tion of Audouinia cap­it­ata, a rare South African spe­cies. Subsequently, smoke has been shown to pro­mote the ger­min­a­tion of many other spe­cies, many of which were pre­vi­ously dif­fi­cult to ger­min­ate. Smoke-stimulated ger­min­a­tion has extens­ive implic­a­tions for hor­ti­cul­ture, weed con­trol, con­ser­va­tion and hab­itat res­tor­a­tion. Much effort has focused on determ­in­ing the chemical(s) in smoke respons­ible for stim­u­lat­ing germination.

Karrikinolide (KAR1, or 3-methyl-2H-furo[2,3-c]pyran-2-one if you prefer) was once con­sidered by some to be the sole chem­ical respons­ible for all smoke-stimulated ger­min­a­tion. Tersonia cyathi­flora, an Australian fire eph­em­eral with an oblig­ate require­ment for smoke to ger­min­ate, is unre­spons­ive to known smoke chem­ic­als such as KAR1. Most related spe­cies are fire eph­em­er­als that ger­min­ate pre­dom­in­antly after fire, often in large num­bers, and live for only a few years, there­after per­sist­ing as seeds in the soil seed-bank until a sub­sequent fire. In addi­tion to T. cyathi­flora, other fire eph­em­er­als in the Gyrostemonaceae, includ­ing Gyrostemon racemi­ger and G. ram­u­losus, ger­min­ate in response to smoke fol­low­ing a period of burial. However, the response of Gyrostemon seeds to KAR1 had not yet been tested pre­vi­ously. Germination stim­u­la­tion of T. cyathi­flora by plant-derived smoke-water, but not KAR1, sug­gests that there may be other chemical(s) in smoke-water that pro­mote the ger­min­a­tion of cer­tain spe­cies. Glyceronitrile (2,3-dihydroxypropanenitrile) was recently isol­ated from smoke-water and stim­u­lates the ger­min­a­tion of a num­ber of spe­cies, includ­ing vari­ous Anigozanthos spp. that are also unre­spons­ive to KAR1. This chem­ical con­tains nitro­gen in addi­tion to car­bon, hydro­gen and oxy­gen, and is pro­posed to oper­ate through the release of cyanide.

New research pub­lished in Annals of Botany tested whether seeds of Gyrostemon racemi­ger and G. ram­u­losus respond to plant-derived smoke-water and/or KAR1; and, secondly, whether seeds of G. racemi­ger were stim­u­lated to ger­min­ate by gly­cer­oni­trile or nitro­gen oxides. The res­ults show that these spe­cies respond to smoke-water but not to KAR1 or to gly­cer­oni­trile. However, mak­ing smoke-water by burn­ing cel­lu­lose alone showed that ger­min­a­tion is stim­u­lated by a com­pound com­posed only of car­bon, hydro­gen and oxy­gen alone. Whether the smoke-stimulated ger­min­a­tion response is an ancient trait or has arisen from con­ver­gent evol­u­tion has been debated. Both smoke and KAR1 respons­ive­ness are phylo­gen­et­ic­ally wide­spread which gives some sup­port to this being an ancient trait.


Comparison of ger­min­a­tion responses of Anigozanthos flavidus (Haemodoraceae), Gyrostemon racemi­ger and Gyrostemon ram­u­losus (Gyrostemonaceae) to smoke-water and the smoke-derived com­pounds kar­rikinolide (KAR1) and gly­cer­oni­trile. (2013) Annals of Botany 111(3): 489–497.
A major germination-promoting chem­ical in smoke-water is 3-methyl-2H-furo[2,3-c]pyran-2-one (kar­rikinolide, KAR1). However, not all spe­cies that ger­min­ate in response to smoke-water are respons­ive to KAR1, such as Tersonia cyathi­flora (Gyrostemonaceae). In this study, a test was made of whether two Gyrostemon spe­cies (Gyrostemonaceae) that have pre­vi­ously been shown to respond to smoke-water, respond to KAR1. If not, then the smoke-derived chem­ical that stim­u­lates ger­min­a­tion of these spe­cies is cur­rently unknown. Recently, gly­cer­oni­trile was isol­ated from smoke-water and pro­moted the ger­min­a­tion of cer­tain Anigozanthos spe­cies (Haemodoraceae). Whether this chem­ical pro­motes Gyrostemon racemi­ger ger­min­a­tion is also examined. Furthermore, an invest­ig­a­tion was car­ried out into whether these spe­cies ger­min­ate in response to smoke-water derived from burn­ing cel­lu­lose alone. Gyrostemon racemi­ger and G. ram­u­losus seeds were bur­ied after col­lec­tion and retrieved in autumn the fol­low­ing year when dormancy was alle­vi­ated and seeds had become respons­ive to smoke-water. Anigozanthos flavidus seeds were after-ripened at 35 °C to alle­vi­ate dormancy. Gyrostemon and Anigozanthos seeds were then tested with ‘Seed Starter’ smoke-water, KAR1, gly­cer­oni­trile and cellulose-derived smoke-water. Although Gyrostemon racemi­ger, G. ram­u­losus and A. flavidus were all stim­u­lated to ger­min­ate by ‘Seed Starter’ smoke-water, none of these spe­cies respon­ded to KAR1. Gyrostemon racemi­ger ger­min­a­tion was not pro­moted by gly­cer­oni­trile. This is in con­trast to A. flavidus, where gly­cer­oni­trile, at con­cen­tra­tions of 1–500 µM, pro­moted ger­min­a­tion, although seed­ling growth was inhib­ited at ≥400 µM. Maximum A. flavidus ger­min­a­tion occurred at gly­cer­oni­trile con­cen­tra­tions of 25–300 µM. Some Gyrostemon ger­min­a­tion was pro­moted by cellulose-derived smoke-water. KAR1 and gly­cer­oni­trile, chem­ic­als in smoke-water that are known to stim­u­late ger­min­a­tion in other spe­cies, did not pro­mote the ger­min­a­tion of G. racemi­ger. This sug­gests that other chemical(s) which pro­mote ger­min­a­tion are present in smoke, and may be derived from burn­ing cel­lu­lose alone.


At this point, it’s time to reward the plant sci­ent­ists “of a cer­tain age” who will have been hum­ming this all the way through read­ing this post:



AJ Cann. ORCID 0000-0002-9014-3720

Alan Cann is a Senior Lecturer in the School of Biological Sciences at the University of Leicester and formerly Internet Consulting Editor for AoB.

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