Smoke-water enhances in vitro pollen germination and tube elongation of three species of Amaryllidaceae

AbstractSmoke-water prepared from burning plant material and smoke-derived compounds significantly promote seed germination and enhance growth of many plant species. Since large amounts of smoke are generated and released into the air during wildfires, it is possible that angiosperm pollen germination and pollen tube elongation may be affected by plant-derived smoke even when the plants are some distance from the fire. We assessed the effect of smoke on pollen germination and pollen tube elongation for three species of Amaryllidaceae that occur naturally in areas prone to winter fire in South Africa. In vitro pollen germination and pollen tube growth of Clivia gardenii, Cyrtanthus mackenii and Scadoxus multiflorus were assessed by preparing hanging drop slides with different concentrations of smoke-water, karrikinolide and 3,4,5-trimethylfuran-2(5H)-one combined with Brewbaker and Kwack's medium and a sucrose and boric acid medium. These slides were incubated for 2h at 25°C. Pollen germination and pollen tube lengths were recorded by capturing images with a compound microscope aided by a digital camera. Low concentrations of smoke-water (1:1000 and 1:2000 v:v) significantly increased pollen germination and pollen tube length in the three species, when applied alone or in combination with either Brewbaker and Kwack's medium or sucrose and boric acid medium. Low concentrations of smoke-water significantly increased in vitro pollen germination and pollen tube growth even when no additional calcium was added. Consequently, smoke from grassland fires may have favourable implications for the reproductive process of flowering plants

Synthesis, X-ray structure determination and germination studies on some smoke-derived karrikins

AbstractThe discovery of the karrikin class of plant growth regulators (PGRs) is a milestone accomplishment in plant biochemistry and physiology, with significant potential in agriculture and horticulture. These compounds have in common a fused furano-pyran ring system featuring various permutations of methyl substitution. Chief amongst these compounds is karrikinolide (KAR1), identified as the key germination stimulant present in plant-derived smoke, which together with five other closely-related structures (KAR2–KAR6) make up the karrikin class of PGRs. By contrast, the germination inhibitor 3,4,5-trimethyl-2(5H)-furanone has also been identified in plant-derived smoke. Various synthetic endeavours have been undertaken for structure–activity relationship study purposes as well as to probe the molecular mechanics of these compounds. In this study, syntheses of KAR1, KAR3 and S-KAR1 were carried out and their structures verified by X-ray crystallography. Effects on germination were measured against the inhibitor 3,4,5-trimethyl-2(5H)-furanone in Grand Rapids lettuce seeds. X-ray crystallographic data and germination promotory activity for S-KAR1 are described for the first time