Germination ecology of five arable Ranunculaceae species

Abstract

Germination and emergence are critical life stages for annual plants and so their full understanding is essential for managing arable plant populations. This study investigated the most important species-specific environmental cues that regulate seed germination and emergence (temperature and light) of the arable Ranunculaceae species Consolida orientalis, Consolida pubescens, Delphinium gracile, Delphinium halteratum ssp. verdunense and Nigella gallica, to propose management strategies for their preservation in agro-ecosystems. Growth chamber and outdoor pot experiments were conducted for two consecutive seasons to analyse light (complete darkness or 12 h light) and temperature (5/ 10, 5/15 and 10/20°C) requirements and emergence patterns. The relative light germination requirement (DG light ), which extends from À100 (complete darkness) to 100 (light), was estimated. Weibull functions were fitted to observed emergence (%) in pots. For all species, germination was higher in complete darkness than with a light regime (À60 < DG light < À95). This dark requirement indicates better germination for buried seeds. A tillage operation just after seed shed is therefore recommended. Consolida spp. germinate and emerge almost exclusively in autumn-winter, while Delphinium spp. and N. gallica can also germinate in spring. These arable plants would be able to adapt to delayed sowings, an important strategy for avoiding early-emerging competitive weeds. Facultative winter-germinating species could face early herbicide treatments if sufficient emergence occurs in winter-spring. These results bring new information to help develop conservation strategies for these species in agro-ecosystems.

Emergence Patterns of Rare Arable Plants and Conservation Implications

“…Also, for species belonging to Papaveraceae, main flushes were detected in autumn and winter, like Papaver argemone, which showed cooler germination requirements according to emergence distribution compared to the other species in this family [25,34]. Consolida species can germinate mainly in autumn-winter, while Delphinium species and N. gallica also germinate in spring [7]. The clustering in this research corroborated this pattern for Consolida species and N. gallica, but not for Delphinium species (Table 2).…”

“…The details (location, coordinates and collection dates) of the 30 species studied, belonging to eight different botanical families, are available at Torra et al [5]. All species studied are naturally occurring as rare in the region [7,17,18,26,37]. Seeds were air-dried for one week after collection, cleaned and then stored in dry conditions with silica gel at room temperature (around 21 • C) until experiments started.…”

“…There are 193 arable plant species either on the national Red Data Lists or considered threatened in at least three of 29 European countries, and of those, 48 are critically endangered (16 are within this study) [6]. Though species-specific recommendations would be appropriate [5,7,25], such a research commitment is hardly attainable considering the numbers of RAP. Therefore, establishing functional groups to manage RAP would be highly desirable for practical recommendations to deliver maximum benefits for the widest range of species potentially present at a site.…”

“…Therefore, an urgent need exists in Europe to prevent the strong decline in plant diversity in arable agro-ecosystems [6]. Particularly needed is the development of conservation and management strategies focused on the threatened RAP species [7].…”

Seed Biology of Lepidium apetalum (Brassicaceae), with Particular Reference to Dormancy and Mucilage Development

“…However, we never observed any seedlings of L. apetalum in the summer, perhaps since environmental conditions are unfavorable for germination. Other weed species that germinate mainly in autumn in nature also showed highest germination percentages at the 10/20 • C temperature regime [33,34]. Seed dormancy status is associated with seasonal temperature changes [2,5,32].…”