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

Abstract

Smoke-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.