Effect of phylogeny, life history and habitat correlates on seed germination of 69 arid and semi-arid zone species from northwest China

Water Stress Inhibits Germination While Maintaining Embryo Viability of Subtropical Wetland Seeds: A Functional Approach With Phylogenetic Contrasts

Wetland species commonly exhibit a range of strategies to cope with water stress, either through drought tolerance or through avoidance of the period of limited water availability. Natural populations provide a genetic resource for ecological remediation and may also have direct economic value. We investigated the effects of drought stress on the seed germination of wetland species. Nineteen species were germinated in four concentrations of polyethylene glycol 6000 (PEG) and were evaluated daily (12-h light photoperiod) or after 35 days (continuous darkness) to determine seed germination under water stress. Germination percentage decreased with an increase in polyethylene glycol 6000 (PEG) concentration, but species' germination response to PEG concentration varied significantly. Seeds recovered their germinability after the alleviation of water stress, but the extent of recovery was species-dependent.

Germination Performances of 14 Wildflowers Screened for Shaping Urban Landscapes in Mountain Areas

Despite the high biodiversity in the Mediterranean region, the use of wildflowers from mountain areas in urban landscaping projects is hampered by the limited information on their seed germination performances. This research evaluated germination traits of 14 native herbaceous wildflower species from northern west Italian alpine and subalpine areas. Seed germination in Petri dishes at 25 °C was performed, applying two different photoperiod conditions (light/dark at 0/24 h or 12/12 h). A high rate and rapid germination are key features for seed and seedling nursery production; thus, the main germination indices were evaluated: the final germination percentage, the index of germination relative to light, the time of first germination, the time to reach 50% of germinated seeds, the germination period, and the mean germination time. Overall, Bellis perennis L., Leucanthemum vulgare Lam., and Taraxacum officinale Weber, from mesophilic mountainous hilly grasslands, and Dianthus carthusianorum L. and Lavandula angustifolia Mill. from higher altitudes, turned out to be interesting. Particular attention could be paid to D. carthusianorum for germination synchrony in both growth conditions, high speed, and short germination period (8.5 and 16.2 days in the dark and in the light, respectively).

Germination Characteristics Is More Associated With Phylogeny-Related Traits of Species in a Salinized Grassland of Northeastern China

Knowing the determinants of seed germination helps us understand plant adaptive strategies to the environment and predict population and community regeneration under climate change. However, multiple factors, including plant and seed traits that influence germination and their relative importance, have received little attention. Here, seed germination experiments were conducted on newly collected seeds for 89 herbaceous species from salinized Songnen grassland. We tested the effects of multiple phylogeny-related plant traits and seed morphological and physiological traits on germination percentage and initial germination time and their relative contribution to shaping germination variation. We found that biennials had higher germination percentages and rates than annuals and perennials. Species with brown seeds had higher germination percentages than those with yellow and black seeds. Eudicots germinated faster than monocots, and seeds with morphophysiological dormancy required more time to initiate germination than those with other kinds of dormancy. Phylogeny-related factors explained more of the variation in germination than seed traits. Seed mass and volume of the large-seeded, but not small-seeded group species were positively correlated with germination percentage. Our findings provide important information for understanding germination variation across species and local adaptation for species in the salinized Songnen grassland.

Bradyrhizobium arachidis mediated enhancement of (oxy)matrine content in the medicinal legume Sophora flavescens

Effect of rhizobial inoculation and nitrate application on the content of bioactive compounds in legume plants is an interesting aspect for interactions among microbes, plants and chemical fertilizers, as well as for cultivated practice of legumes. In this study, nitrate (0, 5 and 20 mmol l^-1 ) and Bradyrhizobium arachidis strain CCBAU 051107^T were applied, individually or in combination, to the root rhizosphere of the medicinal legume Sophora flavescens Aiton (SFA). Then the plant growth, nodulation and active ingredients including (oxy)matrine of SFA were determined and compared. Rhizobial inoculation alone significantly increased the numbers and fresh weight of root nodules. Nodulation was significantly inhibited due to nitrate (5 and 20 mmol l^-1 ). Only oxymatrine was detected in the control plants without rhizobial inoculation and nitrate supplement, while both oxymatrine and matrine were synthesized in plants treated with inoculation of B. arachidis or supplied with nitrate. The content of oxymatrine was the highest in plants inoculated solely with rhizobia and was not significantly altered by additional application of nitrate. Combinations of B. arachidis inoculation and different concentrations of nitrate did not significantly change the concentrations of (oxy)matrine in the plant. In conclusion, sole rhizobial inoculation was the best approach to increase the contents of key active ingredients oxymatrine and matrine in the medicinal legume SFA.

Impacts of growth form and phylogenetic relatedness on seed germination: A large-scale analysis of a subtropical regional flora

Plant regeneration strategy plays a critical role in species survival and can be used as a proxy for the evolutionary response of species to climate change. However, information on the effects of key plant traits and phylogenetic relatedness on seed germination is limited at large regional scales that vary in climate. To test the hypotheses that phylogenetic niche conservatism plays a critical force in shaping seed ecophysiological traits across species, and also drives their response to climatic fluctuation, we conducted a controlled experiment on seed germination and determined the percentage and rate of germination for 249 species in subtropical China under two temperature regimes (i.e., daily 25°C; daily alternating 25/15°C for each 12 hr). Germination was low with a skewed distribution (mean = 38.9% at 25°C, and 43.3% at 25/15°C). One fifth of the species had low (<10%) and slow (4-30 days) germination, and only a few (8%) species had a high (>80%) and rapid (1.2-6.6 days) germination. All studied plant traits (including germination responses) showed a significant phylogenetic signal, with an exception of seed germination percentage under the alternating temperature scenario. Generalized linear models (GLMs) and phylogenetic generalized estimation equations (GEEs) demonstrated that growth form and seed dispersal mode were strong drivers of germination. Our experimental study highlights that integrating plant key traits and phylogeny is critical to predicting seed germination response to future climate change.

Disentangling the influence of ecological and historical factors on seed germination and seedling types in a Neotropical dry forest

In tropical dry forests, although seed germination and seedling establishment are in general limited by the seasonal availability of water, high interspecific variability, nonetheless, exists in terms of seedling traits and germination dynamics. Differences among species in seed germination and seedling traits may be related to other plant life-history traits, such that assessing these relationships may increase our understanding of factors influencing plant establishment, which would affect the regeneration pathways of tropical dry forest communities. In this study, taking into consideration the effect species’ phylogeny, we evaluated the relationships of seed germination metrics (percentage, lag time, and rate of germination) and seedling types (i.e. cotyledons functional morphology), with plant life-history traits (growth form, seed mass, dispersal syndrome and dispersal phenology) for 110 species in a Neotropical dry forest in Mexico. A total of 92% of the species studied disperse their seeds during the dry season, mainly at the beginning of this season (66%), a strategy mostly associated with autochorous herbs. Seed germination was more frequent in species that dispersed seeds at the end of the dry season. Germination percentage was not related to any of the traits studied. However, germination lag time and rate were negatively related to seed mass, a trait that in turn depended on growth form and dispersal syndrome. The dominant seedling type in the community was phanerocotylar epigeal with foliaceous cotyledons (56%), which was mostly associated with small seed mass and herbaceous growth form. Our results provide evidence that several plant life-history traits explain an important part of the variation in seed germination and seedling characteristics observed among species. Therefore, these plant life-history traits may be useful for grouping species in terms of their establishment strategies and roles on the regeneration of tropical dry communities.

Plant attributes and their relationship to the germination response to different temperatures of 18 species from central Mexico

Germination responses of non-dormant seeds to temperature and thermal requirements are affected by the geoclimatic origin of the species, along with specific attributes such as life form, life cycle or seed size. We evaluated the relationship of these attributes and temperature to germination in 18 species that inhabit a convergence area of two biogeographic realms. Seeds were sown at different constant temperatures. Base temperature (T_b ) and thermal time for 50% germination (θ_T(50) ) were determined. For T_b , θ_T(50) and seed size, we performed a cluster analysis and then applied a discriminant analysis (DA). DA was also performed using geoclimatic origin, life form and life cycle as grouping variables. Seed that did not germinate were transferred to the benefit temperature for germination. Finally, ethylene was applied to the remaining seeds that did not germinate. Temperature significantly affected final germination. T_b varied between 5 and 13 °C in 15 species and 19.0-21.5 °C in the remainder; θ_T(50) was 7-30 °Cd in eight species and 50-109 °Cd in the remainder. Cluster analysis showed three groups, and DA evidenced the relevance of T_b and θ_T(50) for this separation. Differences in life cycle were related to θ_T(50) . The geoclimatic origin was not significant. Thermoinhibition or thermodormancy were found in some species. T_b overlaps with environmental temperature of the growth season. Thermal traits for germination mainly reflect the species' life cycle, which is related to the main differences in reproductive performance among annuals and perennials. Local adaptation might mask the effect of geoclimatic origin of a species.

Cracking the case: Seed traits and phylogeny predict time to germination in prairie restoration species

Traits are important for understanding how plant communities assemble and function, providing a common currency for studying ecological processes across species, locations, and habitat types. However, the majority of studies relating species traits to community assembly rely upon vegetative traits of mature plants. Seed traits, which are understudied relative to whole-plant traits, are key to understanding assembly of plant communities. This is particularly true for restored communities, which are typically started de novo from seed, making seed germination a critical first step in community assembly and an early filter for plant establishment. We experimentally tested the effects of seed traits (mass, shape, and embryo to seed size ratio) and phylogeny on germination response in 32 species commonly used in prairie grassland restoration in the Midwestern USA, analyzing data using time-to-event (survival) analysis. As germination is also influenced by seed dormancy, and dormancy break treatments are commonly employed in restoration, we also tested the effects of two pretreatments (cold stratification and gibberellic acid application) on time to germination. Seed traits, phylogeny, and seed pretreatments all affected time to germination. Of all traits tested, variables related to seed shape (height and shape variance) best predicted germination response, with high-variance (i.e., pointier and narrower) seeds germinating faster. Phylogenetic position (the location of species on the phylogenetic tree relative to other tested species) was also an important predictor of germination response, that is, closely related species showed similar patterns in time to germination. This was true despite the fact that all measured seed traits showed phylogenetic signal, therefore phylogeny provided residual information that was not already captured by measured seed traits. Seed traits, phylogenetic position, and germination pretreatments were important predictors of germination response for a suite of species commonly used in grassland restoration. Shape traits were especially important, while mass, often the only seed trait used in studies of community assembly, was not a strong predictor of germination timing. These findings illustrate the ecological importance of seed traits that are rarely incorporated into functional studies of plant communities. This information can also be used to advance restoration practice by guiding restoration planning and seed mix design.

Timing of seed dispersal and seed dormancy in Brazilian savanna: two solutions to face seasonality

BACKGROUND AND AIMS

The relationship between fruiting phenology and seed dispersal syndrome is widely recognized; however, the interaction of dormancy classes and plant life-history traits in relation to fruiting phenology and seed dispersal is understudied. Here we examined the relationship between fruiting season and seed dormancy and how this relationship is modulated by dormancy classes, dispersal syndromes, seed mass and seed moisture content in a Brazilian savanna (cerrado).

METHODS

Dormancy classes (non-dormancy and physical, morphological, morphophysiological, physiological and physiophysical dormancy) of 34 cerrado species were experimentally determined. Their seed dispersal syndrome (autochory, anemochory, zoochory), dispersal season (rainy, dry, rainy-to-dry and dry-to-rainy transitions), seed mass and moisture contents, and the estimated germination date were also determined. Log-linear models were used to evaluate how dormancy and dormancy classes are related to dispersal season and syndrome.

KEY RESULTS

The proportions of dormant and non-dormant species were similar in cerrado. The community-estimated germination date was seasonal, occurring at the onset of rainy season. Overall, anemochorous non-dormant species released seeds during the dry-to-rainy transition; autochorous physically dormant species dispersed seeds during the dry season and rainy-to-dry transition; zoochorous species dispersed non-dormant seeds during the dry and rainy seasons, while species with morphological, morphophysiological or physiological dormancy dispersed seeds in the transitional seasons. Seed mass differed among dispersal seasons and dormancy classes, but seed moisture content did not vary with dispersal syndrome, season or dormancy class.

CONCLUSIONS

The beginning of the rainy season was the most favourable period for seed germination in cerrado, and the germination phenology was controlled by both the timing of seed dispersal and seed dormancy. Dormancy class was influenced by dispersal syndrome and season. Moreover, dormancy avoided seed germination during the rainy-to-dry transition, independently of dispersal syndrome. The variability of dormancy classes with dispersal syndrome allowed animal-dispersed species to fruit all year round, but seeds germinated only during the rainy season. Conversely, seasonally restricted wind-dispersal species dispersed and germinated their non-dormant seeds only in the rainy season.

Phylogeny, habitat together with biological and ecological factors can influence germination of 36 subalpine Rhododendron species from the eastern Tibetan Plateau

The reproductive stages of the life cycle are crucial in explaining the distribution patterns of plant species because of their extreme vulnerability to environmental conditions. Despite reported evidence that seed germination is related to habitat macroclimatic characteristics, such as mean annual temperature, the effect of this trait in controlling plant species distribution has not yet been systematically and quantitatively evaluated. To learn whether seed germination can predict species distribution along altitude gradients, we examined germination data of 36 Rhododendron species in southeastern Tibet originating from contrasting altitudes, habitats, plant heights, seed masses, and phylogenies. Germination varied significantly with altitude, habitat, plant height, and phylogeny and was higher in the light than in the dark. Germination percentage was highest at 10:20°C in the light and 15:25°C in the dark. As altitude increased, germination percentages first rose and then decreased, being highest at 3,500–4,000 m. Germination percentage and rate were highest on rocky slopes, increasing as seed mass and plant height rose. Variations in germination percentage and rate were not significant at subgenera, section, and subsection levels, but they were significant at species level. The results suggested that the relationship between germination and altitude may provide insights into species distribution patterns. Further, germination patterns are a result of long‐term evolution as well as taxonomic constraints.

Photophobia in Lilioid monocots: photoinhibition of seed germination explained by seed traits, habitat adaptation and phylogenetic inertia

Background and Aims

Photoinhibition of seed germination, known to occur notably in species growing in dry and hot habitats, is considered an adaptation to avoid germination at the soil surface after unpredictable rainfall events during the dry season. Hence, the association of this ecophysiological response with plant life histories and the natural environment was investigated in Lilioid monocots, a group of plants where photoinhibition has been pre-eminently observed.

Methods

A data set including germination in light and darkness of about 150 monocots was compiled. Habitat preference, local climate conditions, seed traits and temperature conditions used during germination experiments were retrieved. Factors driving the evolution of photoinhibition were analysed within a phylogenetic framework.

Key Results

Significant phylogenetic signal was found in germination response (λ between 0.76 and 0.80) and photoinhibition (D = 0.406). Photoinhibition was mainly related to plant traits, namely seed coat colour, seed mass and plant height. A relationship with habitat light and moisture was also evident, but the association with climate as well as temperature conditions during incubation was rather poor.

Conclusions

Whilst photoinhibition is prevalent in open habitats, the relationship with habitat moisture conditions and hot and dry climate is weak. Indeed, photoinhibition is also commonly observed in temperate and alpine climate geophytes growing in habitats that are much less susceptible to drought. Hence, phylogenetic inertia, probably mediated by seed morphological traits such as seed coat colour, may explain why temperate climate species have retained photoinhibition inherited from their Mediterranean ancestors.

Phylogeny and source climate impact seed dormancy and germination of restoration-relevant forb species

For many species and seed sources used in restoration activities, specific seed germination requirements are often unknown. Because seed dormancy and germination traits can be constrained by phylogenetic history, related species are often assumed to have similar traits. However, significant variation in these traits is also present within species as a result of adaptation to local climatic conditions. A growing number of studies have attempted to disentangle how phylogeny and climate influence seed dormancy and germination traits, but they have focused primarily on species-level effects, ignoring potential population-level variation. We examined the relationships between phylogeny, climate, and seed dormancy and germination traits for 24 populations of eight native, restoration-relevant forb species found in a wide range of climatic conditions in the Southwest United States. The seeds were exposed to eight temperature and stratification length regimes designed to mimic regional climatic conditions. Phylogenetic relatedness, overall climatic conditions, and temperature conditions at the site were all significantly correlated with final germination response, with significant among-population variation in germination response across incubation treatments for seven of our eight study species. Notably, germination during stratification was significantly predicted by precipitation seasonality and differed significantly among populations for seven species. While previous studies have not examined germination during stratification as a potential trait influencing overall germination response, our results suggest that this trait should be included in germination studies as well as seed sourcing decisions. Results of this study deepen our understanding of the relationships between source climate, species identity, and germination, leading to improved seed sourcing decisions for restorations.

Phylogeny strongly drives seed dormancy and quality in a climatically buffered hotspot for plant endemism

BACKGROUND AND AIMS

Models of costs and benefits of dormancy (D) predict that the evolutionarily stable strategy in long-term stable environments is for non-dormancy (ND), but this prediction remains to be tested empirically. We reviewed seed traits of species in the climatically buffered, geologically stable and nutrient-impoverished campo rupestre grasslands in Brazil to test the hypothesis that ND is favoured over D. We examined the relative importance of life-history traits and phylogeny in driving the evolution of D and assessed seed viability at the community level.

METHODS

Germination and viability data were retrieved from 67 publications and ND/D was determined for 168 species in 25 angiosperm families. We also obtained the percentage of embryoless, viable and dormant seeds for 74 species. Frequencies of species with dormant and non-dormant seeds were compared with global databases of dormancy distribution.

KEY RESULTS

The majority of campo rupestre taxa (62·5 %) had non-dormant seeds, and the ND/D ratio was the highest for any vegetation type on Earth. Dormancy was unrelated to other species life-history traits, suggesting that contemporary factors are poor predictors of D. We found a significant phylogenetic structure in the dormancy categorical trait. Dormancy diversity was highly skewed towards the root of the phylogenetic tree and there was a strong phylogenetic signal in the data, suggesting a major role of phylogeny in determining the evolution of D versus ND and seed viability. Quantitative analysis of the data revealed that at least half of the seeds produced by 46 % of the surveyed populations were embryoless and/or otherwise non-viable.

CONCLUSIONS

Our results support the view that long-term climatic and geological stability favour ND. Seed viability data show that campo rupestre species have a markedly low investment in regeneration from seeds, highlighting the need for specific in situ and ex situ conservation strategies to avoid loss of biodiversity.

Phylogeny, Seed Trait, and Ecological Correlates of Seed Germination at the Community Level in a Degraded Sandy Grassland

Seed germination strongly affects plant population growth and persistence, and it can be dramatically influenced by phylogeny, seed traits, and ecological factors. In this study, we examined the relationships among seed mass, seed shape, and germination percentage (GP), and assessed the extent to which phylogeny, seed traits (seed mass, shape, and color) and ecological factors (ecotype, life form, adult longevity, dispersal type, and onset of flowering) influence GP at the community level. All analyses were conducted on the log-transformed values of seed mass and arcsine square root-transformed values of GP. We found that seed mass and GP were significantly negatively correlated, whereas seed shape and GP were significantly positively correlated. The three major factors contributing to differences in GP were phylogeny, dispersal type, and seed shape (explained 5.8, 4.9, and 3.1% of the interspecific variations independently, respectively), but GP also influenced by seed mass and onset of flowering. Thus, GP was constrained not only by phylogeny but also by seed traits and ecological factors. These results indicated that GP is shaped by short-term selective pressures, and long-term phylogenetic constrains. We suggest that correlates of phylogeny, seed traits, and ecology should be taken into account in comparative studies on seed germination strategies.

Intra-population level variation in thresholds for physical dormancy-breaking temperature

BACKGROUND AND AIMS

Intra-population variation in seed dormancy is an advantage for population persistence in unpredictable environments. The important role played by physically dormant species in these habitats makes understanding the level of variation in their dormancy a key ecological question. Heat produced in the soil is the major dormancy-breaking stimulus and, in fire prone ecosystems, soil temperatures generated by fire may vary spatially and over time. While many studies have investigated variation in initial dormancy, a measure that is of little value in fire-prone ecosystems, where initial dormancy levels are uniformly high, intra-population variation in dormancy-breaking temperature thresholds has never been quantified. This study predicted that species would display variation in dormancy-breaking temperature thresholds within populations, and investigated whether this variation occurred between individual plants from the same maternal environment.

METHODS

The intra-population variation in dormancy-breaking thresholds of five common physically dormant shrub species (family Fabaceae) from fire-prone vegetation in south-eastern Australia was assessed using heat treatments and germination trials. Replicate batches of seeds from each of four maternal plants of Dillwynia floribunda, Viminaria juncea, Bossiaea heterophylla, Aotus ericoides and Acacia linifolia were treated at 40, 60, 80, 100 and 120 °C.

KEY RESULTS

Dormancy-breaking response to heat treatments varied significantly among individual plants for all species, with some individuals able to germinate after heating at low temperatures and others restricting germination to temperatures that only occur as a result of high-severity fires. Germination rate (T50) varied among individuals of three species.

CONCLUSIONS

Variation detected among individuals that were in close proximity to each other indicates that strong differences in dormancy-breaking temperature thresholds occur throughout the broader population. Differences found at the individual plant level could contribute to subsequent variation within the seed bank, providing a bet-hedging strategy, and represent a mechanism for increasing the probability of population persistence in the face of fire regime variability.

Seed dispersal and germination traits of 70 plant species inhabiting the Gurbantunggut Desert in northwest China

Seed dispersal and germination were examined for 70 species from the cold Gurbantunggut Desert in northwest China. Mean and range (3 orders of magnitude) of seed mass were smaller and narrower than those in other floras (5–8 orders of magnitude), which implies that selection favors relatively smaller seeds in this desert. We identified five dispersal syndromes (anemochory, zoochory, autochory, barochory, and ombrohydrochory), and anemochorous species were most abundant. Seed mass (F = 3.50, P = 0.01), seed size (F = 8.31, P < 0.01), and seed shape (F = 2.62, P = 0.04) differed significantly among the five dispersal syndromes and barochorous species were significantly smaller and rounder than the others. There were no significant correlations between seed mass (seed weight) (P = 0.15), seed size (P = 0.38), or seed shape (variance) (P = 0.95) and germination percentage. However, germination percentages differed significantly among the dispersal syndromes (F = 3.64, P = 0.01) and seeds of ombrohydrochorous species had higher germination percentages than those of the other species. In the Gurbantunggut Desert, the percentage of species with seed dormancy was about 80%. In general, our studies suggest that adaptive strategies in seed dispersal and germination of plants in this area are closely related to the environment in which they live and that they are influenced by natural selection forces.

Variation in seed germination of 134 common species on the eastern Tibetan Plateau: phylogenetic, life history and environmental correlates

Seed germination is a crucial stage in the life history of a species because it represents the pathway from adult to offspring, and it can affect the distribution and abundance of species in communities. In this study, we examined the effects of phylogenetic, life history and environmental factors on seed germination of 134 common species from an alpine/subalpine meadow on the eastern Tibetan Plateau. In one-way ANOVAs, phylogenetic groups (at or above order) explained 13.0% and 25.9% of the variance in germination percentage and mean germination time, respectively; life history attributes, such as seed size, dispersal mode, explained 3.7%, 2.1% of the variance in germination percentage and 6.3%, 8.7% of the variance in mean germination time, respectively; the environmental factors temperature and habitat explained 4.7%, 1.0% of the variance in germination percentage and 13.5%, 1.7% of the variance in mean germination time, respectively. Our results demonstrated that elevated temperature would lead to a significant increase in germination percentage and an accelerated germination. Multi-factorial ANOVAs showed that the three major factors contributing to differences in germination percentage and mean germination time in this alpine/subalpine meadow were phylogenetic attributes, temperature and seed size (explained 10.5%, 4.7% and 1.4% of the variance in germination percentage independently, respectively; and explained 14.9%, 13.5% and 2.7% of the variance in mean germination time independently, respectively). In addition, there were strong associations between phylogenetic group and life history attributes, and between life history attributes and environmental factors. Therefore, germination variation are constrained mainly by phylogenetic inertia in a community, and seed germination variation correlated with phylogeny is also associated with life history attributes, suggesting a role of niche adaptation in the conservation of germination variation within lineages. Meanwhile, selection can maintain the association between germination behavior and the environmental conditions within a lineage.

Seed size and photoblastism in species belonging to tribe Cacteae (Cactaceae)

The response of seed germination towards light and the relationship to seed traits has been studied particularly well in tropical forests. Several authors have shown a clear adaptive response of seed size and photoblastism, however, the evolutionary significance of this relationship for species inhabiting arid environments has not been fully understood and only some studies have considered the response in a phylogenetic context. We collected seeds from 54 cacti species spread throughout the tribe Cacteae to test whether there was correlated evolution of photoblastism, seed traits and germination using a reconstructed phylogeny of the tribe. For each species we determined the photoblastic response under controlled conditions, and seed traits, and analyzed the results using phylogenetically independent contrasts. All studied species were positive photoblastic contrasting with the basal Pereskia suggesting an early evolution of this trait. Seeds from basal species were mostly medium-sized, diverging into two groups. Seeds tend to get smaller and lighter suggesting an evolution to smaller sizes. No evidence exists of a relationship between seed size and photoblastic response suggesting that the photoblastic response within members of this tribe is not adaptive though it is phylogenetically fixed and that is coupled with environmental cues that fine tune the germination response.