Plant derived smoke stimulation for seed germination and enhancement of crop growth: A review

Smoke is an important factor involved in fire and post fire germination cues. The role of smoke in stimulating germination was first highlighted in South Africa in a study on Audouinia capitata, a threatened fynbos species. Farmers throughout the world have traditionally used fire and smoke in grain drying practices. It is thought that these methods improve germination and seedling vigor. Smoke has been applied in agriculture mainly by two ways viz., Aerosol method and Smoke water method. In aerosol method, seeds were directly exposed to smoke generated from burning plant material. Smoke-water is one of the most convenient means of application. The biologically active compounds present in smoke readily dissolve in water and when this smoke-extract is used as a diluted solution, treated seeds of many species show a marked improvement in germination. The main active germination compound of smoke-water derived from burned plant materials and cellulose has been identified as butenolide [3-methyl-2H-furo (2, 3-c) pyran-2-one], which is effective at very low concentrations (1 ppb). The compound has recently been referred to as “karrikinolide ”. Following the initial isolation of KAR1, a whole new family of plant growth regulators, termed ‘karrikins ’, were identified in smoke and several related compounds have been synthesized. It is estimated that between 2 and 5 g of KAR1 is more than sufficient for 1 ha of land application rates that are commercially viable. Application of smoke in various agricultural, horticultural forage and forestry crops had found that smoke acted as a cue for breaking seeds of dormancy, improve seed germination, seedling growth, flowering, plant biomass of different plant families, Invitro plantlet regeneration and pathogen control (Anti-microbial properties).