Temperature and storage time strongly affect the germination success of perennial Euphorbia species in Mediterranean regions

Abstract

This study aims to explore the effect of environmental factors (temperature, light, storage time) on germination response and dormancy patterns in eight Mediterranean native wildplants, belonging to the Euphorbia L. genus. In detail, we considered E. amygdaloides subsp. arbuscula, E. bivonae subsp. bivonae, E. ceratocarpa, E. characias, E. dendroides, E. melapetala, E. myrsinites, and E. rigida. We collected seeds from natural plant populations and performed germination assays in climatic chambers at seven constant temperatures (from 5 to 35°C, with 5°C increments), and four fluctuating temperature regimes (8/15, 8/20, 8/25, and 8/30°C, with a 12/12 hr thermoperiod). Germination assays were set up both in dark (D) and in light/dark conditions (L/D, 12/12 hr photoperiod), after short and long seed storage (SS around 30 days and LS around 150 days). For all these species, except E. amygdaloides subsp. arbuscula, results show that the final germinated proportions were improved by a long storage period (>150 days), which supports the existence of nondeep physiological dormancy. Optimal temperature levels ranged from 14.3 to 21.3°C and base temperatures ranged from 5.6 to 12.1°C, while ceiling temperatures from 25.6 to 34.7°C. For none of these species, germinations were favored by an alternating daily temperature regime, while in several instances, germinations were quicker and more complete in darkness, than in an alternating light/dark regime. In some instances, extreme temperature levels (5 and 30°C) induced dormancy and germinations did not resume when seeds were exposed at optimal temperature levels. Results are discussed in terms of the dynamics of emergences and how this might be affected by climate changes.

Conditional Seed Dormancy Helps Silene hicesiae Brullo & Signor. Overcome Stressful Mediterranean Summer Conditions

“…Therefore, germination is delayed until a reliable soil moisture availability is ensured in late autumn. This is in accordance with the fact that thermo-dormancy was not induced, as demonstrated by seeds remaining viable when exposed to unfavorable high temperatures and being able to recover full germination ability, when exposed to optimal thermal values (Table S2), which has previously been found in other Mediterranean species [5].…”

“…Germination, emergence, and seedling establishment are key processes to regulate the spread and distribution of plants into changing environments [1][2][3], which is particularly important for species of conservation concern, such as rare and/or endemic species. Therefore, studying the interactions between the above processes, the genotype, and the environment appears to be particularly relevant to identify potential causes that restrict in situ germination processes [4,5] and to define efficient propagation methods. Likewise, studying the mechanisms that minimize the risk in seedling establishment and increase the probability of successful growth to maturity and reproduction [6] is fundamental, especially in arid and semiarid Mediterranean ecosystems characterized by high environmental unpredictability.…”

“…According to seed dormancy levels, conditionally dormant seeds may vary in their sensitivity to high temperatures. Nevertheless, high thermal values may also result in so-called thermo-inhibition, by which germination is suppressed, although seeds remain viable, and germination is recovered when optimal temperature levels are re-established [5].…”

Variability of Seed Germination and Dormancy Characteristics and Genetic Analysis of Latvian Avena fatua Populations

“…In northern climates, exposure to low positive temperatures is likely to be a major dormancy-breaking factor. The understanding of dormancy mechanisms is important to predict seed behavior with respect to climate change, because both germination and dormancy loss are influenced by temperature and other environmental factors [ 33 ]. In the case of A. fatua in northern climates, dormancy ensures that seeds remain in the soil seed bank throughout the winter when seedlings or plants cannot survive.…”

Population variation in early development can determine ecological resilience in response to environmental change

“…fruticulosa, and Silene fruticosa L. Detailed descriptions of the habitat and ecology for all species are provided in Table 1, and detailed locations of populations are given in Supporting Information Table S1. In terms of dormancy, under natural conditions, the three Euphorbia species have low physiological dormancy (nondeep dormancy), meaning they are dormant only for a short period after ripening (Cristaudo et al, 2019), probably to minimize germination during the hot summer months (del Cacho et al, 2012). Dormancy in the remaining species is also low or absent, because seed dispersal occurs during the dry summer, preventing germination until water is present.…”