5. 5
1
2
3
4
5
6
7
8
9
Table of
Content
Introduction
Synthesis of karrikin from fire
Discovery and etymology of karrikins
Chemical structure of karrikin
Interaction with other hormones
Relation blw karrikins and strigolactone
Effects of karrikins on plants
Research evidences
Conclusion
6. • ‘Fire-followers’ or ‘Fire-ephemerals’.
• Heat, temperature and chemicals (Paul et al., 2007).
• Smoke - Stimulate the germination of seeds (Lange and Boucher, 1990 and
Halford 2010).
• Stable at high temperatures, water soluble, and very active in low concentrations
(Flematti et al., 2004).
6
Introduction - smoke
7. • Plant growth regulators
• Water soluble, thermostable, long lasting, down to
10−9 mol/l
• Molecular weight : 150.1
• Solubility : Chloroform and methanol
• Molecular formula: C8H6O3
• IUPAC name: 3-methyl-2H-furo[2,3-c]pyran-2-one
7
Introduction - karrikins
Structure of karrikin
8. 8
(Flematti et al., 2015)
Bush fire
Smoke - Karrikins
After rain - Seed germination
Anthocercis littorea
Anthocercis littorea
9. 9
Discovery and
etymology of
karrikins
Smoke stimulate seed
germination (De Lange and
Boucher, 1990)
Nitric acid - responsible for
germination
Butenolide - karrikinolide
3-methyl- 2H-furo[2,3-c]pyran-
2-one) (Flematti et al., 2004)
Smoke - ‘karrik’ in Aboriginal
term - Karrikins
10. 10
Synthesis of karrikin from fire
Carbohydrate
Sugar Karrikins
Cellulose
I. hypothesis - Maillard reaction
(carbohydrate and amino acids)
(Light et al., 2005)
II. hypothesis - Cellulose (Halford,
2010).
• Not carried for long distances in smoke (Nelson et
al., 2012).
• Melting point - 118–119 ◦C
11. 11
Karrikin chemical structure
• C, H and O
• KAR1, KAR2, KAR3, KAR4, KAR5 & KAR 6
• Five-membered butanolide ring
• six-membered pyran ring (Waters et al.,
2014).
• 3-methyl-2H-furo[2,3-c]pyran-2-one
(Flematti et al., 2004)
• 3,4,5-trimethylfuran-2(5H)-one (Light et al.,
2010)
TMB
12. 12
Cellulose-
derived
smoke
• Mass and light spectrometric data
• Gas chromatography mass spectrometry
(Flematti et al., 2004).
Smoke-
saturated
water
• Gas chromatography-mass spectrometry
• Nuclear magnetic resonance (NMR)
spectroscopy. (Van Staden et al., 2004)
Quantification of karrikin
KARs - Ultrahigh-performance liquid chromatography-tandem mass spectrometry
(Hrdlicka et al., 2019).
15. • KAR1 - very low concentrations – Production of phytohormones (Chiwocha et al., 2009).
• KAR1 stimulates the germination of light- sensitive seeds - GA (Merritt et al., 2005).
• GA biosynthesis enzymes - GA3ox1 and GA3ox2.
• Endogenous levels of ABA, GA1, GA3 and GA4 not altered.
• Reduces the amounts of exogenous GA3 and GA4 in seeds of Stylidium maritimum
15
Karrikin interaction with other hormones
16. - Karrikins - Cellulose
- Strigolactone - Carotenoids
KAR and SL - butenolide molecule
16
Relation between karrikin and strigolactone
20. • Seed germination in more than 1200 species from 80 genera (Dixon et al., 2009).
• Annual, perennial and shrub life forms (Roche et al., 1997).
• Germination in laboratory and field conditions (Baskin and Baskin, 1998).
• Flowering plants, conifers & horticultural crops - Respond to karrikins (Stevens, 2007
and Nelson, 2012).
• Reactive to smoke in all continents (excluding Antarctica) (Pierce et al., 1995).
20
Effects of smoke & karrikin on plant growth and development
21. • Phylogenetically plant groups - Gymnosperms (Dixon et al., 2009)
Angiosperms (Baskin and Baskin, 1998)
• Variety of ecosystems - Mediterranean vegetation (Catav et al., 2012)
Desert (Pierce et al., 1995)
Alpine (Smedley et al., 1997)
Wetlands (Chiwocha et al., 2009)
• A. thaliana, S. esculentum, Z. mays, O. sativa, L. sativa - non fire followers (Van Staden
et al., 2006).
21
Contd...
22. • Germination of Arabidopsis seeds under favorable conditions (Wang et al., 2018).
• Improved tomato seedling development in temperature extremes (Jain et al., 2006) .
• KAR2 is most active in Arabidopsis (Nelson et al., 2009).
• KAR4 is inactive in Arabidopsis - Stimulate seed germination in L. sativa and S.
orbiculatum (Nelson et al., 2009).
22
Contd...
23. • Arabidopsis - Treated with KAR- ABA level not influenced.
• Avena fatua kernels - Treated with KAR- 1/3 decrease in level of ABA (Nelson et al.,
2009).
• Arabidopsis - Influence chlorophyll concentration (Akeel et al., 2019).
• Carrot - Increase chlorophyll content and net photosynthesis rate, increased stomatal
conductance.
23
Contd...
24. • Arabidopsis - Lower anthocyanin content.
• Carrot roots- Increased Ascorbic acid and β-carotene content (Li et al., 2017).
• KAR - Regulate germination and hypocotyl elongation (Soundappan et al., 2015).
• SL – Root hair development, root growth diameter (Aguilar et al., 2019).
24
KAR SL
1. Regulation of
Leaf morphology
2. Influence the
density of lateral
roots
Contd...
26. 26
Table1: Effects of karrikins (KARs) on the growth and development of
agricultural and horticultural crops
Plant Conc
(M)
Application Examined features Effect
of KAR
Reference
Rice
(Oryza sativa L.)
10−10
–10−8
Grown in Petri
dishes with
KAR1 solution
Seedling weight, vigor index, root
and shoot length, no. of lateral
roots
+ (Kulkarni
et al., 2006)
Tomato
(Lycopersicon
esculentum Mill.)
10−7 Grown in Petri
dishes with
KAR1 solution
Germination 0 (Jain et al.,
2006)
% of abnormal seedlings -
Hypocotyl and radicle length +
Weight of 10 embryonic axis +
27. 27
Plant Conc
(M)
Application Examined features Effect
of
KAR
Reference
Tomato (Lycopersicon
esculentum Mill.),
Okra (Abelmoschus
esculentus L.),
Bean (Phaseolus
vulgaris L.)
Maize (Zea mays L.)
10−7 Tomato, okra, bean and
maize seeds were grown
in Petri dishes with KAR1
solution,
Root and shoot length + (Van Staden
et al., 2006)
Seedling weight of
tomato, okra and maize
+
Seedling weight of bean
vigor index
0
Carrot
(Daucus carota L.
10−10 -
10−7
Seeds presoaked in KAR1
solution for 12 h
Germination, plant height + (Akeel et
al., 2019)
Length, diameter, fresh
and dry weight of root
+
(Fv/Fm), (PN), (gs), total
chlorophyll content
+
Carotenoids, β-carotene
and vitamin C of root
+
28. 28
Table2: Responses of weed seeds to smoke water and KAR1
Family Species Smoke
water
KAR1 References
Amaranthaceae Chenopodium album + 0 Daws et al., (2007)
Asteraceae Chrysanthemum segetum + + Daws et al., (2007)
Senecio jacobinae 0 + Daws et al., (2007)
Brassicaceae Brassica tournefortii + + Stevens et al., (2007)
Sinapis alba 0 + Daws et al., (2007)
Sisymbrium orientale - + Stevens et al., (2007)
Caryophyllaceae Stellaria media + + Daws et al., (2007)
Malvaceae Malva neglecta 0 + Daws et al., (2007)
Papaveraceae Papaver rhoeas 0 + Daws et al., (2007)
Poaceae Avena fatua - + Daws et al., (2007)
Hordeum leporinum + + Stevens et al., (2007)
Sorghum halepense 0 + Daws et al., (2007)
29. • Smoke water- Germination of garden and horticultural seeds.
• Aerosol smoke - Nurseries & landscape restoration operations (Dixon et al., 2009).
• Karrikinolide - 5 – 20 g per hectare (Stevens et al. (2007). (Arctotheca calendula,
Brassica tournefortii, & Raphanus raphanistrum)
29
Uses
Smoke water
32. Treatment details
• SSW (25.8 µg L−1, 51.6 µg L−1,103.2 µg L−1 and 258.0 µg L−1)
• KAR1 (0.015 µg L−1, 0.150 µg L−1, 1.501 µg L−1 and 15.013 µg L−1)
Material and methods
• KAR1 was purchased from Toronto Research Chemicals, Canada.
• SSW – Apparatus
*
Evidence 1: Smoke-saturated water and karrikinolide modulate on
germination, growth, photosynthesis and nutritional values of carrot (Daucus
carota L.)
(Akeel et al., 2019)
33. 33
Fig 1. Effect of SSW and KAR1 on germination percentage (%)
SSW - Control, 25.8 µg L−1, 51.6 µg L−1,103.2 µg L−1 and 258.0 µg L−1
KAR1 - Control, 0.015 µg L−1, 0.150 µg L−1, 1.501 µg L−1 and 15.013 µg L−1
(Akeel et al., 2019)
34. 34
Fig 2. Effect of SSW and KAR on net photosynthesis
SSW - Control, 25.8 µg L−1, 51.6 µg L−1,103.2 µg L−1 and 258.0 µg L−1
KAR1 - Control, 0.015 µg L−1, 0.150 µg L−1, 1.501 µg L−1 and 15.013 µg L−1
(Akeel et al., 2019)
35. 35
Table 3: Effect of SSW on growth parameters of carrot
(Akeel et al., 2019)
36. 36
Table 4: Effect of KAR 1 on growth parameters of carrot
(Akeel et al., 2019)
37. 37
Fig 3. Effect of SSW and KAR1
on nutritional value of carrot
(Akeel et al., 2019)
38. 38
Evidence 2: Karrikins identified in biochars indicate post fire chemical cues
can influence community diversity and plant development
Material and methods
(Kochanek et al., 2016)
39. 39
Fig 4. The yield of karrikinolide (KAR1) isolated from biochar
(Kochanek et al., 2016)
40. 40
Fig 5. Effect of KAR in biochar on tomato
(Kochanek et al., 2016)
41. 41
Evidence 3. Role of smoke stimulatory and inhibitory biomolecules
in phytochrome-regulated seed germination of Lactuca sativa
(Gupta et al., 2019)
Fig 6. Effects of SW, KAR1 & TMB on
germination and ABA levels
Fig 7. Effects of SW, KAR1 & TMB on
hydrolytic enzymes
42. Material and method
0 - 2 cm,
2 - 4 cm,
4 - 6 cm,
6 - 8 cm
42
Evidence 4. Karrikinolide residues in grassland soils following fire
Treatment Conditions under which soil core samples
were collected
No-burn Soil cores collected from no-burn plots
Burnt Soil cores collected from burnt plots
Adjacent
5 m
Soil cores collected from unburnt (5 meters
away)
Adjacent
10 m
Soil cores collected from unburnt (10 meters
away)
(Ghebrehiwot et al., 2013)
43. 43
Table 5: The effect of various soil extracts obtained from four different burning treatments on
germination of Lactuca sativa seeds
Treatments Germination (%) Detected KAR1 (nmol/g soil) Detected TMB (nmol/g soil)
0–2 cm
No-burn 18.7 2.09 104
Burnt 94.7 3.98 276
Adjacent 5 m 53.2 2.45 295
Adjacent 10 m 32 2.52 310
2-4 cm
No-burn 27.7 1.92 127
Burnt 86.7 3.15 380
Adjacent 5 m 33.2 2.60 339
Adjacent 10 m 37.7 2.07 228
4-6 cm
No-burn 20.2 1.92 146
Burnt 72.2 2.46 370
Adjacent 5 m 45.7 2.74 307
Adjacent 10 m 35.2 2.12 206
6-8 cm
No-burn 19.2 1.88 152
Burnt 65.7 2.31 387
Adjacent 5 m 47.7 2.42 334
Adjacent 10 m 37 2.05 283
Ghebrehiwot et al., 2013
44. 44
(Shah et al., 2020)
Evidence 5: Karrikin improves osmotic and salt stress tolerance via the
regulation of the redox homeostasis in the oil plant Sapium sebiferum
Fig 8. Effect on KAR 1 on germination under stress
45. 45
(Shah et al., 2020)
Fig 9. Effect of stress on antioxidant enzymes
46. Advantage
• Land restoration purpose
• Efficient in weed control management
• Arid and semi Arid region
Disadvantage
• Mode of action
• Metabolism is unclear
46
Pros & Cons
47. 47
Conclusion and future perspective
• Plant hormone
• Karrikin can be used as an important management tool for land rehabilitation
and weed control.
• Genomic approaches are the next step towards exploring the mechanism of
action of karrikin.
48. • Akeel, A.; Khan, M.M.A.; Jaleel, H.; Uddin, M. Smoke-saturated Water and Karrikinolide Modulate Germination,
Growth, Photosynthesis and Nutritional Values of Carrot (Daucus carota L.). J. Plant Growth Regul. 2019, 38, 1387–
1401.
• Catav, S.S., Bekar, I., Ates, B.S., Ergan, G., Oymak, F., Ulker, E.D. and Tavsanoglu 2012. Germination response of five
eastern Mediterranean woody species to smoke solutions derived from various plants. Turkish Journal of Botany 36:
480-487.
• De Lange, J.H.; Boucher, C. Auto ecological studies on Audinia capitata (Bruniaceaae), plant-derived smoke as a
germination cue. S. Afr. J. Bot. 1990, 56, 188–202.
• Flematti GR, Merritt DJ, Piggott MJ, Trengove RD, Smith SM, et al. 2011. Burning vegetation produces cyanohydrins
that liberate cyanide and promote seed germination. Nat. Commun. 2:360
• Halford, B. 2010. Smoke Signals. Chemical and Engineering News 88(15): 37–38
• Hrdlicka, J.; Gucký, T.; Novak, O.; Kulkarni, M.; Gupta, S.; van Staden, J.; Dolezal, K. Quantification of karrikins in smoke
water using ultra-high performance liquid chromatography-tandem mass spectrometry. Plant Methods 2019, 15, 81.
• Jager AK, Light ME, Van Staden J. Effects of source of plant material and temperature on the production of smoke
extracts that promote germination of light-sensitive lettuce seeds. Environ Exp Bot. 1996;36:421–9.
48
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Toyooka, K.; Voges, L.; et al. The karrikin receptor KAI2 promotes drought resistance in Arabidopsis
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• Soundappan, I.; Bennett, T.; Morffy, N.; Liang, Y.; Stanga, J.P.; Abbas, A.; Leyser, O.; Nelson, D.C. SMAX1-
LIKE/D53 Family Members Enable Distinct MAX2-Dependent Responses to Strigolactones and Karrikins
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51
Fire is a common disturbance that affects a large proportion of ecosystems (Bond & Keeley 2005; Chuvieco, Giglio, & Justice 2008) and a significant driver of global plant diversity (Pausas & Ribeiro 2017). Even though ∗Corresponding author. E-mail address: sertercatav@mu.edu.tr (S¸.S. C¸ atav). most current fires have an anthropogenic origin, wildfires have affected plant community dynamics since the Paleozoic time (Glasspool, Edwards, & Axe 2004; Pausas & Keeley 2009). Therefore, wildfires have been recognized as a natural phenomenon in terrestrial ecosystems (Keeley, Bond, Bradstock, Pausas, & Rundel 2012), and many plant species have evolved adaptive traits to persist in fire-prone environments. Resprouting from basal lignotubers, serotiny, enhanced flammability, post-fire flowering
Agriculture of the twenty-first century must face new challenges, which require novel solutions
10−10–10−7 M. It was found to be neither toxic nor geno
toxic at 3 × 10−10–10−4 M (Light et al. 2009),
. We now understand
that a group of butenolide compounds isolated from smoke, the first member of which was identified
independently by two researchers’ teams [7,8],
Phytohormones play a dominant role in regulating seed
germination and seedling establishment. Gibberellins (GA) can
break seed dormancy and induce germination (Yamauchi et al.,
2004), while abscisic acid (ABA) can promote seed dormancy and
delay germination (Ali-Rachedi et al., 2004). Auxin [indoleacetic
acid (IAA)] is also involved in regulating seed dormancy (Liu
et al., 2013). Furthermore, IAA has been demonstrated to be
an important regulator in the plant shade avoidance syndrome
that adversely affects seedling development and crop yield (Casal,
2013a; Gommers et al., 2013; Procko et al., 2014). In addition
to phytohormones, other chemical compounds have the ability
to regulate plant growth and development, such as nitrogen
oxide and reactive oxygen species (ROS), both of which have
been demonstrated to regulate seed dormancy and germination
(Bethke et al., 2006; Oracz et al., 2007, 2009; Oracz and Karpi´nski,
2016).
In 2004, chemists purified 3-methyl-2H-furo [2, 3-c] pyran-
2-one from the smoke of burning plant material (Flematti
et al., 2004). Subsequently, several analogs to 3-methyl-2H_x0002_furo [2, 3-c] pyran-2-one were found and collectively named as
karrikins (Flematti et al., 2007; Dixon et al., 2009).
The differences between the six known KARs are
based on methyl substitutions
Moreo_x0002_ ver, smoke water tends to have a ‘dual regulatory’ efect
on germination, as lower concentrations have a germi_x0002_ nation-promoting efect,
KARs are the major germination promoting compound found in smoke, and the KAR receptor is
present in all phylogenetic taxa of plants, including mosses, liverworts, or green algae [13]. Therefore,
the germination of smoke-responsive species is very likely enhanced by KARs
Schematic diagram showing diverse cellular responses to plant-derived smoke. Plantderived smoke triggers regulation of various metabolic processes resulting in acceleration of seed germination and other growth processes. Upward and downward arrows indicate increased and decreased metabolic processes in response to plant-derived smoke, respectively. The dashed lines represent the possible relationship between smoke induced changes at molecular level and their effects. Abbreviations are as follows: K/PDS, karrikins/plant-derived smoke; KAI2, α/β hydrolases receptors of karrikins; MAX2, F-box subunit of a SCF class of E3 ubiquitin-protein ligase complex; SMAX1, a growth suppressor protein; a
Under
abiotic stresses, applications of karrikins did not increase the endogenous abscisic acid level but altered the expression of several ABA signaling genes, such as SNF1-
RELATED PROTEIN KINASE2.3, SNF1-RELATED PROTEIN KINASE2.6, ABI3, and
ABI5, suggesting potential interactions between karrikins and ABA signaling in the
SNF1-
RELATED PROTEIN KINASE2.3, SNF1-RELATED PROTEIN KINASE2.6, ABI3, and
ABI5
, KAR1 is ~10-fold more effective than KAR2 in Grand Rapids lettuce, and 100-fold more effective in S. orbiculatum (Flematti et al. 2007
KAR1 was also shown to improve germination of tomato seed and subsequent seedling vigour when grown at low (10 C) or high (40 C
KAR2 stimulates germination of Arabidopsis seeds under favorable conditions, but it can inhibit
germination in the presence of osmolytes or at elevated temperature. KAI2 signaling may inhibit
germination under unfavorable conditions as protection against abiotic stress [60]. However,
germination and seedling growth of tef, an African cereal crop, under high temperature, and low
osmotic potential were observed to be enhanced by KAR1 treatment [61]. The enhanced germination
and improved tomato seedling development in temperature extremes connected with KAR1 utilization
were also reported [62]. These facts show that the reactions of a model plant and crops can be different.
The level of ABA in imbibed seeds of Arabidopsis was not affected by KARs treatment [53]. That
was not a case of Avena fatua kernels treated by KAR1, which showed a one-third decrease in the level
of ABA after 16 hours of imbibition
KAR signaling can also influence secondary metabolism. Kai2 mutant of Arabidopsis has lower
anthocyanin content as a result of transcription misregulation of the anthocyanin biosynthesis
pathway [71]. Ascorbic acid and β-carotene content were increased in carrot roots grown from KAR1
primed seeds [73]. The content of tashinone I, pharmacologically active terpenoid, was significantly
increased in hairy roots of Salvia miltiorrhiza by a signaling pathway involving nitric oxide and jasmonic
acid [75
Germination of Arabidopsis seeds and growth of seedlings in
response to karrikin. Arabidopsis thaliana seeds with primary dormancy
incubated for seven days on water-agar without karrikin (KAR)
germinate very poorly whereas those with KAR germinate readily
(top row). Seedlings germinated on nutrient medium and grown
in low light for seven days without KAR have long hypocotyls whereas
those with KAR have short hypocotyls and larger cotyledons
(bottom row). Images from the author’s laboratory
The realisation that many plant species respond to karrikins
led to the discovery that seeds of Arabidopsis thaliana can
respond [5]. Arabidopsis is the geneticist’s dream because of
the resources and knowledge that are available. Arabidopsis
seeds with a small amount of dormancy will respond to
KAR1 or KAR2, provided that there is no nitrate present,
which causes seeds to germinate regardless of the karrikin.
Selection of Arabidopsis mutants that fail to respond to
karrikins led to the discovery of two genes that are essential
for karrikin action. One gene, named MORE AXILARY
GROWTH2 (MAX2), was already known for its role in
responses to strigolactone hormones [13], while the other,
KARRIKIN-INSENSITIVE2 (KAI2), was similar to the gene
coding for the strigolactone receptor, known as DWARF14
[11]. These discoveries led to the idea that karrikins simply
mimic strigolactones, because they both have a butenolide
ring (Fig. 2). We now know that this is not the case in
Arabidopsis. Karrikins and strigolactones are perceived
separately and the plant responds differently to the two
classes of compound, but the two systems are obviously
very closely related [11]. Formally we still do not know if
the mode of action of karrikins in fire-followers is the same
as that in Arabidopsis, but all plants apparently contain a
KAI2 gene, so it seems likely
Utilization of KARs in dose 2–20 g haa 1 as weed control measure was proposed for agriculture [16].
Such use of KARs seems to be highly improbable as the cost of KARs would have to decrease thousands
fold to reach an affordable level, and, even then, economic benefit for farmers would be questionable.
More likely, KARs can be used as a priming agent for seeds of agricultural and horticultural crops in
order to enhance germination and early seedling growth to establish a steady field under conditions of
climate change
Measurements of karrikins in soil are technically very challenging but seed-germination bioassays can be used to detect activity, one study suggesting that active compound(s) can persist in the soil for over seven years after a fire [Preston and Baldwin, 1999]. Karrikins are unstable in ultraviolet light [Scaffidi et al., 2012] so they might be expected to decay rapidly in natural sunlight; however, smoke contains many aromatic 0compounds that can absorb ultraviolet light and could protect karrikins by acting as organic ‘sunscreens’. On the other hand, karrikins can be washed away by rain and elute through sandy soils relatively quickly, so their concentration will steadily decline.
The active compound(s) can persist in the soil for over seven years after a fire .
Karrikins are unstable in ultraviolet light [Scaffidi et al., 2012] so they might be expected to decay rapidly in natural sunlight; however, smoke contains many aromatic compounds that can absorb ultraviolet light and could protect karrikins by acting as organic ‘sunscreens’.
On the other hand, karrikins can be washed away by rain and elute through sandy soils relatively quickly, so their concentration will steadily decline. (author)
r germination. Plants were grown in a peat mixture without
biochar (control) or with peat replaced at 3, 10 or 30% by either a green waste biochar high in KAR1 or a sugarcane biochar low in KAR1. All mixtures
contained fertiliser to neutralise potential nutritional aspects of biochar [19]. Values represent means ± SEM (n = 5 biological replicates). Analysis of
variance and means tested the effect of biochar type and rate of application on (a) shoot length; (b) hypocotyl length; (c) leng
Effects of SW, KAR1, and TMB on germination (n 5 4) and
ABA (n 5 3) levels in cv Grand Rapids lettuce seeds under different light
conditions for 24 h at 25°C. After 3 h of incubation in the dark, seeds
were exposed to R or FR light treatment for 1 h and were replaced in the
dark. Bars (germination 6 SE) and symbols (ABA 6 SE) for each light
condition with different letters are signifificantly different according to
Bonferroni correction (P , 0.05). DW, Dry weight.
Now it is widely accepted by the plant physiologist that karrikins found in plant burning smoke has the ability to stimulate seed germination. Identification of these compounds helps to understand the possible effects on ecosystems and important tool for further investigation. This is of rising importance increased human activity and increased demands for food are increasing the frequencies and distribution of fires. However, global warming and precipitation changes are predicted to increase the frequency of wildfires (Pechony and Shindell 2010). Karrikins can be used as an important management tool for land rehabilitation and weed control. It is also to find that how stable they are in the soil and they are metabolized by plants and micro-organisms, and how they affect other organisms. Genomic approaches are the next step towards exploring the mechanism of action of karrikins. An important criterion to further find out that does the time of exposure to smoke have the influence on germination? The study of adoptability ability of a karrikin exposed species to different environmental stress (such as – drought, salt
and temperature stress) conditions is also important.
