The discovery that plant derived smoke elicits striking increase in seed germination was significant. Further many species across genera and continents respond to plant derived smoke or plant derived smoke water. These species have been found in all continents (except Antarctica), representing a wide diversity of fire and non-fire-prone ecosystems. Plant derived smoke can also enhanced seedling vigor; smoke solutions stimulate flowering, rooting and somatic embryogenesis. In Watsonia borbonica (spring-flowering hybrid) smoke-water increased flowering from 20% to 90%.
Aqueous smoke solutions show hormone like responses in different species and interact with auxins, gibberellins, cytokinins, ABA and ethylene in different types of seeds. Further smoke water also breaks the dormancy of seeds in some plants. Plant smoke-water treatment enhances photosynthesis may be by improved stomatal conductance and the enhanced level of the photochemical efficiency of PSII in leaves. Smoke treatments enhancing promoted the yield of tomatoes under greenhouse conditions. Smoke solutions have shown promising results on the growth of onion plants and bulbs. Smoke can protect seeds and seedlings against microbial attack. Smoke generated by combusting wood and a mixture of odoriferous and medicinal herbs eliminated some of the bacteria that are harmful to agricultural and horticultural plants.
In 2003 Karrikinolide (the butenolide, 3-methyl-2H-furo [2, 3-c]pyran- 2-one, KAR1) was first identified as the potent germination stimulant present in plant-derived smoke. Many synthetic karrikins have been synthesized that show germination activity. KAR1 acts on concentrations as low as 1 ppb. Plant-derived smoke compounds affects variety of changes in seeds, like change in sensitivity of seeds to hormones, light requirements, and seed coat characteristics. Studies on lettuce have shown that plant-derived smoke extracts can increase endogenous GA levels and decrease ABA levels. However further experimentation is needed in this respect.
Strigolactone and Karrikins share structural similarity. Both are potent stimulants for seed germination. While karrikins stimulates germination in wide range of species strigolactone appears to be more selective stimulant of germination. Both Strigolactone and karrikins signal molecule require a single LRR type F-box gene (MAX2) and an α/β hydrolase fold protein (KAI2 or DAD2/D14) for signal transduction. Use of Karrikins in modern agriculture is relatively new and needs to be further investigated. The antimicrobial properties of smoke may reduce bacterial and fungal infections occurring on crops, potentially reducing the need for fungicides and other chemicals. Karrikins are now firmly established as an important family of naturally occurring plant growth regulators.There can be variety of applications of Karrikins in enhancing crop productivity which depends upon our progressive understanding of the Karrikins phenomenon. The discovery of karrikins enthused researchers with an exciting relationship between plant growth regulation hormones involved in it, fire ecology, plant evolution, and molecular plant physiology.
Sheila D.S. Chiwocha, Kingsley W. Dixon, Gavin R. Flematti, Emilio L. Ghisalberti, David J. Merritt, David C. Nelson, Julie-Anne M. Riseborough, Steven M. Smith, Jason C. Stevens. (2009). Karrikins: A new family of plant growth regulators in smoke. Review Plant Science 177 252-256
De Lange JH, Boucher C (1990). Autoecological studies on Audouinia capitata (Bruniaceae). Plant-derived smoke as a germination cue. South Afr J Bot 5: 700-703.
S.M. Pierce, K. Esler, R.M. Cowling (1995). Smoke induced germination of succulents (Mesembryanthemaceae) from fire-prone and fire-free habitats in South Africa, Oecologia 102 520-522.
S. Roche, K.W. Dixon, J.S. Pate (1997). Seed ageing and smoke: partner cues in the amelioration of seed dormancy in selected Australian native species, Aust. J. Bot. 45 783-815.
C.C. Baskin, J.M. Baskin (1998). Seeds: Ecology, Biogeography and Evolution of Dormancy and Germination, Academic Press, San Diego.
K.W. Dixon, S. Roche (1995). The role of combustion products (smoke) in stimulating exsitu and in-situ germination of Western Australian plants, Proc. Int. Plant Prop. Soc. 45 53-56.
G.R. Flematti, E.L. Ghisalberti, K.W. Dixon, R.D., Trengove Vinylogous 4H-pyrones and their preparation and use in promoting plant growth, filed 22nd December
2003, WO 2005061515A1 (2005).
G.R. Flematti, E.L. Ghisalberti, K.W. Dixon, R.D. Trengove (2004).A compound from smoke that promotes seed germination, Science 305 977.
Sparg, S.G., M.G. Kulkarni, M.E. Light and J. Van Staden. (2005). Improving seedling vigour of indigenous medicinal plants with smoke. Bioresource Technology, 96: 1323-1330.
Keeley, J.E. (1993). Smoke-induced flowering in the firelily Cyrtanthusventricosus. South African J. Bot., 59: 638-639.
Taylor, J.L.S. and J. Van Staden. (1996). Root initiation in Vignaradiata (L.) Wilczek hypocotyl cuttings is stimulated by smoke-derived extracts. Plant Growth Regulation, 18: 165-168.
Senaratna, T, K. Dixon, E. Bunn and D. Touchell. (1999). Smokesaturated water promates somatic embryogenesis in geranium. Plant Growth Regulation, 28: 95-99.
F.E. Drewes, M.T. Smith, J. van Staden, (1995) The effect of a plant derived smoke extract on the germination of light-sensitive lettuce seed, Plant Growth Regul. 16 205-209.
M.J. Gardner, K.J. Dalling, M.E. Light, A.K. Jager, J. van Staden (2001). Does smoke substitute for red light in the germination of light-sensitive lettuce seeds by affecting gibberellin metabolism? S. Afr. J. Bot. 67 636-640.
L.M. Egerton-Warburton, A smoke-induced alteration of the sub-testa cuticle in seeds of the post-fire recruiter, Emmenanthe penduliflora Benth (Hydrophyllaceae), J. Exp. Bot. 49 (1998) 1317-1327.
Nelson DC, Scaffidi A, Dun EA, Waters MT, Flematti GR, et al. (2011). F-box protein MAX2 has dual roles in karrikin and strigolactone signaling in Arabidopsis thaliana. Proc. Natl. Acad. Sci. USA 108:8897-902
Hamiaux,C., Drummond,R.S., Janssen,B.J., Ledger,S.E.,Cooney, J.M.,Newcomb, R.D.,etal.(2012). DAD2 is an alpha/betahydrolase likely to be involved inthepercep- tion of the plant branching hormone, Strigolactone. Curr.Biol. 22, 2032-2036.
Waters, M. T., Nelson, D. C., Scaffidi, A., Flematti, G. R., Sun, Y. K., Dixon, K. W., et al. (2012b). Specialisation within the DWARF14 protein family confers distinct responses to karrikins and strigolactonesinArabidopsis. Development 139, 1285-1295.
Daws MI, Pritchard HW, Van Staden J (2007) Butenolide from plant-derived smoke functions as a strigolactone analogue: Evidence from parasitic weed seed germination. South Afri J Bot 74: 116-120.
Doherty, L.C. and M.A. Cohn. (2000). Seed dormancy in red rice (Oryza sativa). XI. Commercial liquid smoke elicits germination. Seed Sci. Res., 10: 415-421.
Drewes, F.E., M.T. Smith and J. VanStaden. (1995). The effect of plant-derived smoke extract on the germination of light sensitive lettuce seed. Plant Growth Regulation, 16: 205-209.
Jie Zhou1, Lei Fang, Xiao Wang, Lanping Guo1 & Luqi Huang (2013). Effects of Smoke-Water on Photosynthetic Characteristics of Isatis indigotica Seedlings. Sustainable Agriculture Research; Vol. 2, No. 2
Kulkarni, M.G., Ascough, G.D., Van Staden, J., (2008). Smoke-water and a smoke-isolated butenolide improve growth and yield of tomatoes under greenhouse conditions. HortTechnology 18, 449-454.
Kulkarni, M.G., Ascough, G.D., Verschaeve, L., Baeten, K., Arruda, M.P., Van Staden, J., (2010). Effect of smoke-water and a smoke-isolated butenolide on the growth and genotoxicity of commercial onion. Scientia Horticulturae 124, 434-439.
Light, M.E., Kulkarni, M.G., Ascough, G.D., Van Staden, J., (2007). Improved flowering of a South African Watsonia with smoke treatment. South African Journal of Botany 73, 298.
Kulkarni, M.G., Light, M.E., Van Staden, J. (2011) Plant-derived smoke: Old technology with possibilities for economic applications in agriculture and horticulture. South African Journal of Botany 77 (972-979.
Roche, S., Koch, J.M., Dixon, K.W., (1997). Smoke enhanced seed germination for mine rehabilitation in the southwest of Western Australia. Restoration Ecology 5, 191-203.
Nautiyal, C.S., Chauhan, P.S., Nene, Y.L., (2007). Medicinal smoke reduces airborne bacteria. Journal of Ethnopharmacology 114, 446-451.
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