Multiple fire-related cues stimulate germination inChaenorhinum rubrifolium(Plantaginaceae), a rare annual in the Mediterranean Basin

Abstract

In Mediterranean fire-prone ecosystems, annual species specific to post-fire habitats should have a soil seed bank and should be able to germinate after a fire. Therefore, various fire-related cues can be expected to stimulate germination in post-fire annuals. Germination patterns of the rare annual Chaenorhinum rubrifolium (Plantaginaceae) were examined in response to mechanical scarification, heat shock, aqueous smoke, nitrogenous compounds, gibberellic acid, karrikinolide (KAR1), and mandelonitrile (a cyanohydrin analogue, MAN) under dark and photoperiod conditions in the laboratory. Combinations of these treatments were also included in the experiment. Strong physiological dormancy in the seeds of C. rubrifolium was partially broken by several fire-related germination cues, including smoke and nitrate, under light conditions. KAR1 and MAN also stimulated germination, and the highest improvement in germination was achieved in the KAR1 treatment in the presence of light. Heat shock + smoke and KAR1 + MAN combinations had positive synergetic and additive effects on germination under light conditions, respectively. The light played a crucial role in the promotion of germination. The results suggest that multiple fire-related cues operate to stimulate germination in C. rubrifolium, an annual species from the Mediterranean Basin. However, the species may have a broader germination niche than a fire-restricted one.

Effect of fire-derived chemicals on germination and seedling growth in Mediterranean plant species

“…Because of the slow release of free cyanide from cyanohydrin solutions (Flematti et al 2011), for the MAN and KAR1 + MAN treatments, seeds were first incubated in distilled water and KAR1 solution (0.1 µM), respectively, for 24 h, and then transferred to an agar medium (0.8%) containing 50 µM of MAN. The concentrations chosen for each treatment were based on previous studies (Flematti et al 2004(Flematti et al , 2011Downes et al 2013;Cembrowska-Lech, Koprowski, & Kępczyński 2015;Ç atav, Küçükakyüz, Tavşanoglu, & Akbaş 2015;Tavşanoglu et al 2017).…”

“…The existence of smoke-responsive species that do not respond to KAR1 (Downes, Lamont, Light, & Van Staden 2010;Flematti et al 2011) led to the discovery of a new germination cue, the cyanohydrin glyceronitrile (2,3-dihydroxypropanenitrile) (Flematti et al 2011). Furthermore, the stimulatory effects of cyanohydrin analogues, such as glycolonitrile, acetone cyanohydrin, 2,3,4-trihydroxybutyronitrile and mandelonitrile (hereafter 'MAN'), on germination have also been determined in several studies (Flematti et al 2011;Baldos, DeFrank, & Sakamoto 2015;Tavşanoglu et al 2017).…”

“…Cistaceae, Fabaceae), in which the germination cue is more likely to be heat than smoke. Furthermore, there is lack of information about the effects of specific smoke-derived compounds (KAR1 and cyanohydrin) on the germination of Mediterranean plant species except Chaenorhinum rubrifolium (Tavşanoglu et al, 2017). These shortcomings limit our ability to understand the evolutionary aspects of fire in the Mediterranean Basin and correctly frame this region among other Mediterranean-type ecosystems worldwide (Moreira & Pausas 2018).…”

Taxonomic notes on the genus Chaenorhinum (Plantaginaceae) in Turkey

“…In fact, these species are relatively rare despite their wide range from SW Europe and NW Africa to SW Asia (Speta 1980, Sutton 1988, Benedí-González 1991. Our research indicated that seeds of this species have a high-level of dormancy, and they germinate only when some fire-related germination cues are applied (Tavşanoğlu et al 2017). This germination behaviour of this annual species can explain why it is scarce, and can be found in recently burned Mediterranean sites (Céspedes et al 2014, Tavşanoğlu et al 2017.…”

“…Our research indicated that seeds of this species have a high-level of dormancy, and they germinate only when some fire-related germination cues are applied (Tavşanoğlu et al 2017). This germination behaviour of this annual species can explain why it is scarce, and can be found in recently burned Mediterranean sites (Céspedes et al 2014, Tavşanoğlu et al 2017. Fernandes (1971) defined three subspecies and two forms for European C. rubrifolium, and following his treatment, Sutton (1988) divided the species into four subspecies: subsp.…”