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.


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