Seed afterripening and germination photoinhibition in the genusCrocus(Iridaceae)

Abstract

Mediterranean characteristics are attributed to the genusCrocus, which is inadequately studied in terms of seed germination. An afterripening requirement is very common in environments with warm and dry periods, and photoinhibition has been detected in many angiosperms inhabiting dry and open areas. The effects of afterripening and light on seed germination were investigated for the first time in 23 native GreekCrocustaxa, collected from various localities with either a Mediterranean or a temperate climate. Germination experiments were conducted in continuous darkness and in light at the optimal temperature for each taxon, with both freshly collected and afterripened seeds; warm stratification (20°C, darkness) was also examined in 22 taxa. A number of selected taxa were additionally investigated with respect to afterripening outdoors, afterripening and warm stratification at higher temperatures (35 and 25°C, respectively), stratification at 20/10°C, dry storage at low temperatures, response to gibberellic acid and phenology of embryo growth. It was postulated that an afterripening requirement is a characteristic of the genusCrocus, and we found that it can be fulfilled in nature during the Mediterranean dry summer. Also, for the vast majority of the taxa, warm stratification and stratification at 20/10°C can both meet the afterripening requirement. Embryos of the taxa studied are underdeveloped and have to grow prior to germination. Intrageneric differences of seed germination were observed only towards light, with photoinhibition being predominant in taxa from drier environments.

Plant regeneration from seeds responds to phylogenetic relatedness and local adaptation in Mediterranean Romulea (Iridaceae) species

“…Nevertheless, despite the fact that the embryo does not entirely fill the seed (as it is the case in many other seeds of plant species belonging to the family Iridaceae, see Martin ; Vandelook and Van Assche ; Carta et al. ; Skourti and Thanos ), embryo elongation in these Romulea species is not required for radicle emergence. A broader phylogenetic comparative study is required to understand the extent of this phenomenon in relation to the geographic origin and to the application of seed dormancy classification (Baskin and Baskin ).…”

“…Instead, seed germination is to some degree reduced in the presence of light, especially at warmer temperatures and/or under alternating temperature regimes. Both dark and constant temperature preferences for germination denote an advantageous strategy to avoid radicle emergence at the soil surface and thus decreases the likelihood of seedling mortality due to irregular inconstant water availability (Doussi and Thanos ; Fenner and Thompson ; Skourti and Thanos ).…”

“…However, the phylogenetic regression revealed a weak embryo growth for the genus as a whole because the analysis also included data of the out-group (Crocus), for which embryo growth was reported (Carta et al 2014). Nevertheless, despite the fact that the embryo does not entirely fill the seed (as it is the case in many other seeds of plant species belonging to the family Iridaceae, see Martin 1946;Carta et al 2014;Skourti and Thanos 2015), embryo elongation in these Romulea species is not required for radicle emergence. A broader phylogenetic comparative study is required to understand the extent of this phenomenon in relation to the geographic origin and to the application of seed dormancy classification (Baskin and Baskin 2004).…”

Optimization of Plant Production by Seed Treatment in Two Wild Subspecies of Narcissus pseudonarcissus Rich in Alkaloids

“…Another trait that may affect the response of seeds to light is the pigmentation of the seed coat, which influences both the spectral composition and quantity of light transmitted [ 34 ]. Photoinhibition is related to black or dark colored seed [ 33 , 35 ] and it is more frequent in certain lineages, such as in monocot taxa in the order Asparagales, which includes the family Amaryllidaceae [ 33 ].…”

Effect of temperature and scarification on seed germination of Conanthera spp. (Tecophilaeaceae)

“…they germinate in winter and plants senesce in spring or summer, after seed set. Similar behavior is seen in other Mediterranean geophytes from Chile, such as Leucocoryne spp., Trichopetalum plumosum, Pasithea coerulea and Schizanthus litoralis (Jara et al, 2006;De la Cuadra et al, 2016) and others geophytes as Crocus spp., Narcissus spp., Scilla autumnalis and Urginea maritima (Marques and Draper, 2012;Skourti and Thanos, 2015).…”