Plant responses to water stress: changes in growth,dry matter production,stomatal frequency and leaf anatomy

The responses of seedlings of three fast growing tree species,Eucalyptus hybrid(E. camaldulensis × E. teriticornis), Casuarina equisetifolia andMelia azedarach, to different levels of soil moisture in controlled glasshouse conditions were compared. The survival percentage, height of plants, number of leaves per plant, number of branches, fresh mass and dry mass of roots, stems, branches and leaves decreased in the three species with increasing water stress. Stomatal frequency and length of stomata inEucalyptus andMelia also decreased with increasing water stress. However, no significant difference was obtained in the width of stomata and the ratio of number of open stomata to total number of stomata per unit area. The leaf thickness decreased, but the thickness of palisade parenchyma increased with increasing water stress inEucalyptus hybrid andCasuarina. Leaf thickness ofMelia did not show any significant variation due to water stress.     

Latitudinal variation in seeds characteristics of Acer platanoides and A. pseudoplatanus

Climate change will likely affect population dynamics of numerous plant species by modifying several aspects of the life cycle. Because plant regeneration from seeds may be particularly vulnerable, here we assess the possible effects of climate change on seed characteristics and present an integrated analysis of seven seed traits (nutrient concentrations, samara mass, seed mass, wing length, seed viability, germination percentage, and seedling biomass) of Acer platanoides and A. pseudoplatanus seeds collected along a wide latitudinal gradient from Italy to Norway. Seed traits were analyzed in relation to the environmental conditions experienced by the mother trees along the latitudinal gradient. We found that seed traits of A. platanoides were more influenced by the climatic conditions than those of A. pseudoplatanus. Additionally, seed viability, germination percentage, and seedling biomass of A. platanoides were strongly related to the seed mass and nutrient concentration. While A. platanoides seeds were more influenced by the environmental conditions (generally negatively affected by rising temperatures), compared to A. pseudoplatanus, A. platanoides still showed higher germination percentage and seedling biomass than A. pseudoplatanus. Thus, further research on subsequent life-history stages of both species is needed. The variation in seed quality observed along the climatic gradient highlights the importance of studying the possible impact of climate change on seed production and species demography.     

濒危树种格木天然群体自由授粉子代苗期生长变异

格木是我国热带和南亚热带地区主要的珍稀濒危树种之一,具有重要的经济和生态价值。本文应用从格木主要天然分布区收集的6个群体的种子进行育苗试验,揭示格木天然群体子代芽苗和幼苗生长变异状况及其与种子性状、亲本环境因子间的相关性。结果表明,格木天然群体子代芽苗和幼苗表型性状在群体间和群体内均存在丰富的变异,苗高的变异高于地径,苗期选择以高生长为主。格木苗期生长与种子的大小、千粒重相关显著,胚根长度与经度、地径与年均气温、高径比与海拔均存在显著的相关性(p＜0.05)。研究结果为深入开展格木良种选育奠定了基础,亦将有助于其天然资源的保护经营和人工种植业的发展。     

Improving seed germination and seedling growth of Lepidium sativum with different priming methods under arsenic stress

This study was carried out to determine the effects of seven kinds of priming, gibberellic acid (GA), salicylic acid (SA), citric acid (CA), sodium chloride (NaCl), potassium chloride (KCl), zinc (Zn) and iron (Fe) on seed germination and seedling emergence of garden cress (Lepidium sativum) under arsenic stress. Results revealed that germination percentage (GP), seed vigor index (SVI), radicle length (RL), plumule length (PL) and tolerance index (TI) were significantly decreased when arsenic stress was augmented from 0 to 100 mg L^?1. Nevertheless, primed seeds (hormo, nutri and halo-priming) increased seed germination and seedling emergence and tolerance index of L. sativum. Phytotoxicity was also reduced by priming practices. Meanwhile, priming with gibberellic acid (GA) had the most positive effects on measured traits. Generally, the order of the effect of priming treatments tested decreases by the following order: GA > CA > KCl > Fe > Zn > SA > NaCl. The result of this study is coherent with the hypothesis that under heavy metal stress, priming can develop seed germination performance and seedling emergence.     

Quantitative trait loci associated with seed and seedling traits in Lactuca

Seed and seedling traits related to germination and stand establishment are important in the production of cultivated lettuce (Lactuca sativa L.). Six seed and seedling traits segregating in a L. sativa cv. Salinas x L. serriola recombinant inbred line population consisting of 103 F8 families revealed a total of 17 significant quantitative trait loci (QTL) resulting from three seed production environments. Significant QTL were identified for germination in darkness, germination at 25 and 35°C, median maximum temperature of germination, hypocotyl length at 72 h post-imbibition, and plant (seedling) quality. Some QTL for germination and early seedling growth characteristics were co-located, suggestive of pleiotropic loci regulating these traits. A single QTL (Htg6.1) described 25 and 23% of the total phenotypic variation for high temperature germination in California- and Netherlands-grown populations, respectively, and was significant between 33 and 37°C. Additionally, Htg6.1 showed significant epistatic interactions with other Htg QTL and a consistent effect across all the three seed production environments. L. serriola alleles increased germination at these QTL. The estimate of narrow-sense heritability (h²) of Htg6.1 was 0.84, indicating potential for L. serriola as a source of germination thermotolerance for lettuce introgression programs.     

Phenotypic variation of seed traits of Haloxylon ammodendron and its affecting factors

The typical desert-inhabiting shrub Haloxylon ammodendron (C. A. Mey.) Bunge is an important species that is endangered in Northwest China. In this study, variance, correlation and cluster analysis were employed to examine phenotypic variations of H. ammodendron seed traits from 14 populations in China to investigate their relationships with environmental and genetic factors. The average coefficient of variation was higher among regions (26.9%) than within regions (19.8%). Correlation analysis revealed that the diameter/thickness and fruit wing length were significantly correlated with environmental factors. A cluster dendrograms designed based on seed traits was consistent with the finding from environmental and genetic data obtained using Ward's method and the unweighted pair-group method with arithmetic means. A Mantel test revealed correlation between seed traits and environmental data (r = 0.53, P < 0.01) was greater than that between seed traits and genetic data (r = 0.25, P < 0.05). Thus, seed traits associated with morphology, mass, and germination varied significantly among the populations, are strongly affected by climatic and geographical factors, and were moderately correlated with genetic diversity. These results provide insights for designing appropriate conservation strategies for H. ammodendron.     

Right here,right now: Populations of Actinotus helianthi differ in their early performance traits and interactions

Populations across the geographical distribution of a species are shaped by different local environments to produce distinctive patterns of variation in plant traits. Among‐population variation is, therefore, important for understanding potential shifts in distributions under changing environments, but is often not included in studies. In particular, critical data on the suitability of local environments for plant traits expressed at different life stages are lacking. To address this we performed two experiments to disentangle the influence of the local environment on multiple plant traits for populations of Actinotus helianthi from across its latitudinal range. A common environment experiment was used to compare early plant traits of germination, early seedling growth and survival for 17 populations of A. helianthi. To examine how biotic interactions vary across populations, we evaluated whether plant traits, including height and number of pseudanthia, influence visitor diversity and abundance, and if insect visitor abundance or diversity was associated with seed set success. We found that populations varied in germination success between 0.2 ± 0.1% and 64.2 ± 2.3%. Seedling growth and early survival varied among populations by as much as a factor of two and 44 respectively. We recorded variation in plant traits across hierarchical spatial scales from the maternal plant to biogeographical regions. The abundance and diversity of insect visitors also varied among populations and seed set was found to be site specific. There was a trend for populations with taller plants and larger floral display sizes to be more frequently visited by pollinators. We also identified a positive linear relationship between the number of visits by flies and seed set success. These results suggest that the local environment has a strong role in directly and indirectly influencing variation in plant traits within populations of A. helianthi, and potentially other perennial species.     

Altitudinal variations in germination and growth responses ofReynoutria japonica populations on Mt Fuji to a controlled thermal environment

The authors examined altitudinal variations in the thermal responses of seed germination and seedling growth inReynoutria japonica (=Polygonum cuspidatum) under controlled environmental conditions. Seed populations were collected from different altitudes on Mt Fuji in Japan. The mean seed weight of the upland populations (above 1500 m) was significantly (1.5-fold) heavier than that of the lowland populations (below 1400 m). Under the lowest temperature regime of 15/10°C (day/night) the upland populations showed a significantly higher percentage and speed of germination than the lowland populations; this was not significant under higher temperature regimes. These results indicate that the germination traits of the upland populations on Mt Fuji are favorable for colonization in their cold habitats (low temperature and short growing season). Growth and shoot development were compared between the seedlings grown from seeds collected at altitudes of 700 and 2420 m. The upland seedlings showed a significantly larger biomass and leaf area than the lowland seedlings at 15°C, but there was no difference at 25°C. The difference in biomass at 15°C was attributed to the difference in seed weight. The upland seedlings produced a significantly larger number of branches with smaller and more numerous leaves at both 15°C and 25°C. these developmental traits of the upland seedlings were considered to represent the adaptation of the life form to upland environments. It was concluded that theR. japonica populations along an altitudinal gradient on Mt Fuji can be classified into two ecotypes, whose distribution border lies at an altitude of about 1400–1500m. In this study, the seed weight and germination traits of twoR. japonica seed populations collected in Chiba Prefecture were briefly compared with those of the lowland populations on Mt Fuji.     

Seed weight and germination behavior of the submerged plant Potamogeton pectinatus in the arid zone of northwest China

Variation in seed weight is common within and among plant species, but few studies have attempted to document the pattern of seed weight and germination attributes for aquatic macrophytes at a large scale. This study examined within‐species variation in seed weight and germination attributes and the effects of environmental factors on seed traits of the submerged plant Potamogeton pectinatus in the arid zone of northwest China. Our results showed that the average seed weight was 0.24 g per 100 seeds with a coefficient of variation (CV) of 28.4% among the eight P. pectinatus populations. The total germination fraction of seeds of P. pectinatus was relatively poor, less than 35% in seven P. pectinatus populations, and the lowest germination percentage found was only 2%. There were significant differences in seed weight, time to onset of germination, and total germination fraction among the eight different populations. Hierarchical partitioning analysis showed a strongly positive correlation between seed weight and water temperature and pH. Seed weight and the maternal environmental factors significantly affected both time to initiation of germination and total germination fraction. Our results suggest that (1) seed weight variation in P. pectinatus primarily is the result of temperature variation during fruit development; (2) relatively poor germination fraction suggests that seeds are relatively unimportant in the short‐term survival of populations and that it may be another adaptive trait allowing plants to take place in the right place and at the right time, especially in harsh environment; and (3) variation in seed germination traits should be determined by local environmental and intrinsic factors that interact in a complex fashion.     

Intrinsic and extrinsic drivers of recruitment across the distribution range of a seed-dimorphic herb

Recruitment of new individuals, through germination and seedling survival, is a key process for short-lived plants. Here, we analyzed intraspecific variation in recruitment across the latitudinal range of Plantago coronopus, a widespread herb that produces both large basal seeds with a mucilaginous coat and small apical seeds without coat. We experimentally tested the effects of seed traits and water availability on recruitment, by using seeds from a wide environmental stress gradient from N Africa to N Europe. Our experiments were carried out in controlled environmental conditions and in dunes where the species naturally occurs. Water shortage decreased seed germination and seedling survival for all populations, showing the importance of water supply for P. coronopus. Basal seeds showed higher and faster germination rates than apical seeds. Since among-population variation in seed mass was not related to potential germination rate, it is the mucilaginous coat rather than size difference that likely drives the differential success between seed morphs. Seed mass positively affected seedling survival instead, but only in controlled conditions with regular water supply. An experiment in a dune showed indeed that the highest survival corresponded to the local population and not the one with the largest seeds. Our results demonstrate that both intrinsic and extrinsic factors drive inter-population variation in the early life stages of this short-lived plant, allowing it to adapt across the environmentally heterogeneous distribution range. Gathering information on intraspecific variation in recruitment-related traits will help us to understand and predict plant responses in a context of climatic change.     

Evolution and ecology of seed internal morphology in relation to germination characteristics in Amaranthaceae

Background and AimsInternal seed morphological traits such as embryo characteristics and nutritive tissue can vary considerably within a plant lineage. These traits play a prominent role in germination processes and the success of seedling establishment, and are therefore under high selective pressure, especially in environments hostile to seedlings, such as arid, saline or highly dynamic habitats. We investigated the relationships of seed internal morphology and germination characteristics of 84 species of Amaranthaceae s.l., a family with numerous lineages that have adapted to stressful growing conditions.MethodsWe used seed cross-sections to assess embryo type and the ratios of embryo to seed surface and radicle to cotyledon length. Furthermore, seed mass, mean time to germination, habitat preferences and further plant traits such as C₃ or C₄ photosynthesis and life form were compiled for each species. Data were analysed using phylogenetic comparative methods.Key resultsWe found embryo type (λ = 1), log seed mass (λ = 0.86) and the ratio of embryo to seed size (λ = 0.78) to be evolutionarily stable, with an annular embryo as ancestral in the family. Linked to shifts to the three derived embryos types (spiral, horseshoe-shaped and curved) is an increase in the ratio of root to cotyledon length and a reduction of nutritive tissue. We observed stabilizing selection towards seeds with relatively large embryos with longer radicles and less nutritive tissue that are able to germinate faster, especially in lineages with C₄ photosynthesis and/or salt tolerance.ConclusionsWe conclude that the evolutionary shift of nutrient storage from perisperm to embryo provides an ecological advantage in extreme environments, because it enables faster germination and seedling establishment. Furthermore, the evolutionary shift towards a higher ratio of root to cotyledon length especially in small-seeded Amaranthaceae growing in saline habitats can provide an ecological advantage for fast seedling establishment.     

侧柏不同器官水提取物对油松种子萌发和幼苗生长的他感效应

研究了侧柏（Platycladus orientalis）根、枝、叶、果实不同浓度水提取物及枝叶挥发油对油松种子萌发和幼苗生长的他感效应。结果表明：侧柏各器官及挥发油都含有化感物质,均对油松种子萌发及幼苗生长表现出“高抑低促”效应,而且低浓度时的促进作用明显强于高浓度时的抑制作用。与对照相比,在浓度为2 mg·mL^-1时,侧柏根水提取物对油松幼苗根长和鲜重的促进能力最强,其根长和鲜重分别比对照提高了79.78%和376.60%;侧柏叶水提取物对油松幼苗苗高促进能力最强,比对照提高了102.41%;侧柏枝水提取物对油松种子发芽的促进能力最强,发芽率比对照提高了65.63%。而在浓度为30 mg·mL^-1时,除了侧柏根和枝水提取物对油松种子萌发（87.50%）和鲜重（85.11%）表现出明显的抑制作用外,其它提取物对油松幼苗根长和苗高生长的抑制作用均不明显。侧柏枝叶挥发油对油松种子萌发,幼苗生长均表现为促进作用,特别对油松种子萌发具有显著的促进作用,其促进率达70.37%。说明侧柏和油松混交,可能有利于油松树木生长及生产力的提高。     

大金发藓和小蛇苔化学他感作用的生物测定

以绿豆、油菜和萝卜种子为生测材料,以大金发藓（Polytrichum commune Hedw.）和小蛇苔(Conocephalum japonicum(Thunb.) Grolle.)的水提取液为处理液,测定了二种苔藓植物提取液在三种浓度下对三种作物种子萌发率、萌发指数、萌发势、种子活力、幼苗根重和鲜重和根长等指标的影响。发现绿豆是理想的生测材料,种子活力指数、幼苗鲜重、根重和根长是理想的生测指标;二种苔藓植物的水提取液表现出类似于激素样的作用方式,对种子萌发和幼苗生长,表现为低浓度下促进、高浓度时抑制的化学他感效应。     

Variation in dormancy and germination in three co-occurring perennial forest herbs

Mesic deciduous forest herbs often disperse seed with morphophysiological dormancy (MPD) that prevents germination during unfavorable periods for seedling survival. However, for seeds of some species with MPD, seasonal separation of root and shoot emergence and variation in dormancy levels can complicate interpretation of seedling emergence timing in the field. We tested whether dormancy-break and germination requirements differed among co-occurring perennial forest herbs, Actaea racemosa, Hydrastis canadensis, and Sanguinaria canadensis, which are wild-harvested for their medicinal properties and known to have MPD. Seeds of all species exhibited a summer → autumn → winter requirement for seedling emergence in spring. However, species differed in seed-bank persistence due to variation in primary dormancy levels and stratification requirement of seeds. A. racemosa and H. canadensis can form short-term persistent seed bank, whereas S. canadensis can form a long-term persistent seed-bank, regardless of whether elaiosomes were removed from seeds prior to burial. A. racemosa seeds are dispersed in autumn with weak physiological dormancy, as seeds germinated to high rates at 15/6°C after 8 weeks. In contrast, most seeds of the summer dispersed species, H. canadensis and S. canadensis, require summer temperatures to overcome physiological dormancy. Consequently, seedling emergence is reduced and delayed by 1 year if seeds are not sown immediately following the period of natural dispersal. Seedling emergence was much lower in the field than in controlled conditions for all species, especially in the small-seeded A. racemosa. Interspecific variation in dormancy levels and germination traits must be considered when establishing populations for conservation purposes and in understanding recruitment limitation in perennial forest herbs.     

Germination,survival, and growth of grass and forb seedlings: Effects of soil moisture variability

Seed germination and seedling growth, survivorship, and final biomass and their responses to watering interval were studied in two grass and six forb species to assess germination and seedling growth responses to increased soil moisture variability as might occur with future increases in precipitation variability. Seeds were planted in prairie soil and watered at 1, 2, 4, or 7 d intervals (I). Seed germination peaked at I = 4 d whereas leaf growth in grasses and forbs, and final biomass in grasses peaked at I = 7 d, suggesting that growth and biomass were favored at greater soil moisture variability than seed germination. Biomass responses to I were stronger than the germination responses, suggesting that soil moisture variability more strongly influenced post germination growth. Individual species responses to I fell into three groups; those with responses to I for: (1) seed germination and seedling survival, (2) biomass, or (3) both germination and biomass production. These species groups may be more useful than life form (i.e., grass/forb) for understanding seed germination and seedling dynamics in grasslands during periods of soil moisture variability. Seed germination and early growth may assume more importance in grassland plant community dynamics under more variable precipitation patterns.     

Matching floral and pollinator traits through guild convergence and pollinator ecotype formation

Background and Aims

Pollinator landscapes, as determined by pollinator morphology/behaviour, can vary inter- or intraspecifically, imposing divergent selective pressures and leading to geographically divergent floral ecotypes. Assemblages of plants pollinated by the same pollinator (pollinator guilds) should exhibit convergence of floral traits because they are exposed to similar selective pressures. Both convergence and the formation of pollination ecotypes should lead to matching of traits among plants and their pollinators.

Methods

We examined 17 floral guild members pollinated in all or part of their range by Prosoeca longipennis, a long-proboscid fly with geographic variation in tongue length. Attractive floral traits such as colour, and nectar properties were recorded in populations across the range of each species. The length of floral reproductive parts, a mechanical fit trait, was recorded in each population to assess possible correlation with the mouthparts of the local pollinator. A multiple regression analysis was used to determine whether pollinators or abiotic factors provided the best explanation for variation in floral traits, and pollinator shifts were recorded in extralimital guild member populations.

Key Results

Nine of the 17 species were visited by alternative pollinator species in other parts of their ranges, and these displayed differences in mechanical fit and attractive traits, suggesting putative pollination ecotypes. Plants pollinated by P. longipennis were similar in colour throughout the pollinator range. Tube length of floral guild members co-varied with the proboscis length of P. longipennis.

Conclusions

Pollinator shifts have resulted in geographically divergent pollinator ecotypes across the ranges of several guild members. However, within sites, unrelated plants pollinated by P. longipennis are similar in the length of their floral parts, most probably as a result of convergent evolution in response to pollinator morphology. Both of these lines of evidence suggest that pollinators play an important role in selecting for certain floral traits.     

暴马丁香不同种源种子和幼苗的表型性状变异及其与地理-气候因子的相关性

为探究不同产地暴马丁香﹝Syringa reticulata subsp. amurensis ( Rupr.) P. S. Green et M. C. Chang〕种子和幼苗的表型性状变异规律及其与地理-气候因子的关系,以来源于黑龙江、河北、北京、内蒙古、青海和山西的10个种源(包括6个野生种源和4个栽培种源)的种子和幼苗为实验材料,对种子长和宽、种翅长和宽、百粒质量、发芽率、叶长和宽、叶长与叶宽的比值、叶柄长、株高和地径12个表型性状进行测量;在此基础上,进行了方差分析、变异系数分析、主成分分析、聚类分析及相关性分析。结果显示：暴马丁香不同种源间种子和幼苗的表型性状均有极显著差异(P=0.01),差异较大的表型性状为发芽率、百粒质量、种翅长和种翅宽。种源内和种源间各表型性状的变异系数(CV)均差异较大,种源内CV值为1.39%~45.56%,种源间CV值为6.45%~42.76%;其中,种源内种翅长和种翅宽的CV平均值较大,发芽率和百粒质量的CV平均值均较小,而种源间发芽率和百粒质量的CV值则较大。主成分分析结果表明：暴马丁香表型性状间的差异主要体现在种子长、种子宽和叶长,其次为株高、发芽率、地径、叶宽和种翅宽。根据聚类分析结果,供试的10个种源被划分为4类,其中,来源于北京和内蒙古及3个来源于河北的种源聚为Ⅰ类,来源于黑龙江哈尔滨的2个种源聚为Ⅱ类,来源于山西的2个种源聚为Ⅲ类,来源于青海的1个种源单独聚为Ⅳ类,聚类结果与各种源的地理分布有关。相关性分析结果表明：各表型性状间及表型性状与地理-气候因子间均存在不同的相关性,其中,种子发芽率与种子的其他5个表型性状均无显著相关性;经度和纬度与各表型性状均无显著相关性,而海拔、年均温和无霜期则是影响表型性状变异的主要因子。综合分析结果显示：暴马丁香各种源间存在明显的地理遗传分化,地理隔离和生态因子的大幅变化导致其种子和幼苗的表型性状变异丰富。根据研究结果,对暴马丁香的保护和利用提出了一些建议。     

Effects of germination time on seed morph ratio in a seed-dimorphic species and possible ecological significance

Background and Aims Diaspores of heteromorphic species may germinate at different times due to distinct dormancy-breaking and germination requirements, and this difference can influence life history traits. The primary aim of this study was to determine the effect of germination time of the two seed morphs of Suaeda corniculata subsp. mongolica on life history traits of the offspring.Methods Germinated brown and black seeds were sown on the 20th of each month from April to September in a simulated but near-natural habitat of the species. Phenological and vegetative traits of the maternal plants, and number, size and germination percentage of the offspring were determined.Key Results Germinated seeds sown late in the year produced smaller plants that had a higher proportion of non-dormant brown than dormant black seeds, and these brown seeds were larger than those produced by germinated seeds sown early in the year. The length of the seedling stage for brown seeds was shorter than that for black seeds, and the root/shoot ratio and reproductive allocation of plants from brown seeds were more variable than they were for plants from black seeds. Late-germinating brown seeds produced larger plants than late-germinating black seeds.Conclusions Altering the proportion of the two seed types in response to germination timing can help alleviate the adverse effects of delayed germination. The flexible strategy of a species, such as S. corniculata, that produces different proportions of dimorphic seeds in response to variation in germination timing may favour the maintenance and regeneration of the population in its unpredictable environment.     

Effects of seed mass on seedling height and competition in European white oaks

The relationship between seed size and fitness in plants may depend on offspring density, especially in cases where seed size affects the outcome of competition. We investigated the relationship between seed mass, germination, intraspecific competition and seedling height in a glasshouse experiment on three European white oak species (Quercus robur, Q. petraea, Q. pubescens). Within offspring families, seed mass showed a moderate, but statistically significant effect on seedling height, i.e. seedlings from heavier seeds were slightly taller. In contrast, competition caused pronounced inequality in seedling height in pairs of competing seedlings, but in only 55.2% of all pairs the dominant competitor arose from the heavier seed. It is thus possible that a positive effect of seed mass on seedling growth can be mediated through the density of conspecific seedlings and that heterogeneity in offspring density will contribute to the maintenance of seed mass variation in oak populations.     

Is fire a selective force of seed size in pine species?

Fire is selectively shaping most of the traits of plants growing in fire-prone environments. However, seed size and other features related to seed production have not been studied in the light of the evolutionary role of fire. Our research tests the hypothesis that larger seeds have a higher chance of surviving wildfires and produce more vigorous seedlings with a lower death rate. To test this hypothesis the germination and early seedling growth of five Spanish pine species were studied. Weight, length and width of all seeds were measured. The biomass (fresh and dry weight) and length (root and total) of subsequent seedlings were also measured after 30 d from emergence. Seeds were submitted to elevated temperatures for periods in which the chance of survival was 50 % (calculated by means of a logistic model for each pine species). The differences observed among species suggests that fire may be adaptively shaping seed size in pines with larger seeds (Pinus canariensis and P. pinaster), because larger seeds are more likely to survive after heat shocks. Furthermore, in P. canariensis, seedlings after heat treatment are even larger than those submitted to control. In P. halepensis, despite being well adapted to fire, our results indicated no relationships between fire and seed characteristics. Finally, although heat treatment has a general adverse effect on seedling growth in the case of the two subalpine pines, we have detected a positive relationship between seed size and seedling growth but only in the largest seeds. This might also suggest the relevance of fire as a selective force for these pines which is outperformed by the relevance of dispersal and emergence time as adaptive traits in the post-fire scenario.