Glaucium flavum Seed Germination - an Ecophysiological Approach

The yellow horned-poppy Glaucium flavum Crantz shows a final dark germination which is of characteristically ‘mediterranean’ type (maximal response at the temperature range 5–15 °C), though a considerable broadening is brought about, both by a red light pulse and a stratification treatment. Seeds imbibed in darkness at 25 °C for even a few hours are induced to develop a secondary dormancy (thermodormancy) which can be released by light and stratification. The well known time dependence of light sensitivity and the gradually imposed induction of light indifference at supraoptimal temperatures have also been shown. Seeds imbibed under regimes simulating those met naturally in Greece during November or April, do not germinate when illuminated with white light (ζ = 1·26). Full manifestation of germination occurs either in complete darkness or under various, red-enriched light conditions (ζ higher than 2·07). A partial promotion is observed with very low fluence rates of white light (in the order 10−2−10−4 of daylight). The existence of a surface-avoiding seedling emergence mechanism based on light-inhibited seed germination was verified in a pot experiment under natural conditions, with seeds buried to various depths. Only those seeds buried at 0·5 cm germinate optimally and readily after the onset of the rainy season (November-December) although those at 1 and 2 cm also germinate to a considerable extent