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| 3. |
- Caron, M. M., et al.
(författare)
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Impacts of warming and changes in precipitation frequency on the regeneration of two Acer species
- 2015
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Ingår i: Flora. - : Elsevier BV. - 0367-2530 .- 1618-0585. ; 214, s. 24-33
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Tidskriftsartikel (refereegranskat)abstract
- Climate projections indicate that temperatures will increase by up to 4.5 degrees C in Europe by the end of this century, and that more extreme rainfall events and longer intervening dry periods will take place. Climate change will likely affect all phases of the life cycle of plants, but plant reproduction has been suggested to be especially sensitive. Here, using a combination of approaches (soil heaters and different provenances along a latitudinal gradient), we analyzed the regeneration from seeds of Acer platanoides and A. pseudoplatanus, two tree species considered, from a management point of view, of secondary relevance. We studied germination, seedling survival and growth in a full-factorial experiment including warming and changes in watering frequency. Both species responded to warming, watering frequency and seed provenance, with stronger (negative) effects of warming and provenance than of watering frequency. In general, the central provenances performed better than the northernmost and southern-most provenances. We also detected interactive effects between warming, watering frequency and/or seed provenance. Based on these results, both species are expected to show dissimilar responses to the changes in the studied climatic factors, but also the impacts of climate change on the different phases of plant regeneration may differ in direction and magnitude. In general increases in the precipitation, frequency will stimulate germination while warming will reduce survival and growth. Moreover, the frequent divergent responses of seedlings along the latitudinal gradient suggest that climate change will likely have heterogeneous impacts across Europe, with stronger impacts in the northern and southern parts of the species' distribution ranges.
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| 4. |
- Dayamba, Sidzabda Djibril, et al.
(författare)
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Effects of aqueous smoke solutions and heat on seed germination of herbaceous species of the Sudanian savanna-woodland in Burkina Faso
- 2010
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Ingår i: Flora. - : Elsevier BV. - 0367-2530 .- 1618-0585. ; 205, s. 319-325
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Tidskriftsartikel (refereegranskat)abstract
- Smoke generated by burning of plant materials has widely been recognized as a germination cue for some species from both fire prone and fire-free ecosystems. It is an important factor for the understanding of vegetation dynamics and could have potential use for ecological management and rehabilitation of disturbed areas. Individual species, however, seem to have a specific requirement for the type and dosage of smoke treatments. In the present study, six different concentrations of smoke solution were tested on 13 herbaceous species by soaking the seeds for 24 h. The germination of a forb species, Borreria scabra, was significantly stimulated (p < 0.05) by the smoke treatment while that of the annual grass species, Euclasta condylotricha, was significantly inhibited (p < 0.05) by 100% smoke solution treatment. Contrary to our expectation that another fire-related cue, heat shock, would break the physical dormancy of the species tested, it was not promotive. For non-dormant seeds of B. scabra and Borreria radiata, high temperatures were lethal while low temperature induced physiological dormancy that was overcome in the former species within 30 days of the germination trial. For some species, responses to smoke did not corroborate with the field-observed response to fire, making ecological interpretation challenging. For responsive species, the smoke treatment could be a simple approach for promoting their re-establishment in areas where it is needed. More investigations are needed to assess the spread of response to smoke. (C) 2010 Elsevier GmbH. All rights reserved.
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- Eckstein, Rolf Lutz, et al.
(författare)
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Evidence for consistent trait-habitat relations in two closely related violets of contiguous habitat types from a fertilisation experiment
- 2004
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Ingår i: Flora. - 0367-2530 .- 1618-0585. ; 199:3, s. 234-246
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Tidskriftsartikel (refereegranskat)abstract
- Most studies on the adaptive significance of plant traits compared species that differed in inherent growth rate or species of habitats at the extremes of environmental gradients. In the present paper, we compared the response of Viola elatior and V. pumila, two closely related and morphologically similar violets to the experimental variation of nitrogen availability. The species occur in adjacent habitat types, viz. alluvial forest fringes (V. elatior) and floodplain meadows (V. pumila), that differ in resource availability and disturbance across a relatively small gradient. We tested the hypotheses that, according to their typical habitat, V. elatior should show more traits of a stress tolerant competitive plant, while V. pumila should exhibit more ruderal traits. We carried out a two-year common garden experiment with two levels of fertiliser addition (N5, 5 g N m(-2) yr(-1); N20, 20 g N m(-2) yr(-1)), and analysed a number of traits related to relative growth rate (RGR), allocation, and nutrient use. We further did an experiment with seeds from the experimental plants to study variation in germination rate. We found considerable ontogenetic drift in the species during two years of growth. In the first year, both species showed similar mass and growth rate but these were achieved through different trait combinations. In the second year, V. elatior had a higher RGR, produced more biomass per unit nutrient and developed more leaf area per unit plant mass than V. pumila, while the latter produced thinner leaves. V. pumila had a higher capacity for nutrient acquisition, but a large proportion of the captured nutrients were used for reproduction. Germination rate was higher in V. pumila than in V. elatior, independent of the nutrient status of the mother plant, while seeds of V. elatior from N20 plants had a significantly higher germination rate (67%) than seeds from N5 plants (35%). Our data suggested that many of the analysed trait differences seem to be consistent with the requirements of the different habitat types.
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- Hensgen, Frank, et al.
(författare)
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Distribution of gastropods in floodplain compartments and feeding preferences for river corridor plant species : Is there an effect of gastropod herbivory on the distribution of river corridor plants?
- 2011
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Ingår i: Flora. - : Elsevier. - 0367-2530 .- 1618-0585. ; 206:6, s. 534-543
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Tidskriftsartikel (refereegranskat)abstract
- Herbivory through gastropods has among others been proposed as a potential factor responsible for the river corridor distribution of plant species, which is a well known but poorly understood ecological pattern. Since floodplains are characterised by seasonally changing abiotic conditions, viz, floods during winter and spring and severe summer drought that are unsuitable for gastropods they may present safe habitats for highly palatable plant species. In the present study we compared species composition of gastropods and vegetation of twelve grassland sites situated within three floodplain compartments along the Upper Rhine. Additionally, we studied the palatability of 7 days and 25 days old seedlings of five typical floodplain plant species and five mesic grassland species to the slug Deroceras reticulatum in laboratory experiments. Our results showed that both vegetation and gastropod community composition but not gastropod diversity and abundance differed between floodplain compartments. Owing to omnivory of most gastropods the similarity structure of sites based on plants and gastropods was not significantly correlated. In general, slug herbivory significantly reduced survival and biomass of 7 days old seedlings, but responses were species-specific. In contrast, with the exception of Arabis nemorensis, Viola pumila and Taraxacum sect. Ruderalia biomass of 25 days old seedlings was not significantly affected by slug herbivory. Although the response of floodplain plant species as a group to slug herbivory did not differ from common grassland species, our results suggest that gastropods may potentially influence the distribution pattern of the highly palatable river corridor species Arabis nemorensis and Viola pumila. However, further research is needed to estimate the damage to river corridor plants through gastropod herbivory and its effect on competitive relationships under natural conditions.
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| 7. |
- Karlsson, Laila, et al.
(författare)
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Variation within species and inter-species comparison of seed dormancy and germination of four annual Lamium species
- 2008
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Ingår i: Flora. - : Institutionen för fysik, kemi och biologi. - 0367-2530 .- 1618-0585. ; 203:5, s. 409-420
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Tidskriftsartikel (refereegranskat)abstract
- In an ecological context, knowledge of intra-species variation in dormancy and germination is necessary both for practical and theoretical reasons. We used four or five seed batches (replicates) of four closely related annuals co-occurring in arable fields in Sweden: Lamium amplexicaule, L. confertum, L. hybridum and L. purpureum. Seeds used for experiments stemmed from plants cultivated on two sites, each site harbouring one population of each species, thereby ensuring similar environmental history of seeds. Seeds were tested for germination when fresh and after three different pre-treatments (cold or warm stratification, or dry storage) for up to 24 weeks. Seeds were also sown outdoors. Despite substantial intra-species variation, there were clear differences between species. The general seed dormancy pattern, i.e. which environmental circumstances that affect dormancy, was similar for all species; dormancy reduction occurred during warm stratification or dry storage. Even though the response to warm stratification indicate a winter annual pattern, successful plants in Sweden were mostly spring emerged. Germination in autumn occurred, but plants survived winters poorly. Consequently, as cold stratification did not reduce dormancy, strong dormancy in combination with dormancy reduction during dry periods might explain spring germination. It is hypothesized that local adaptations occur through changes mainly in dormancy strength, i.e. how much effort that is needed to reduce dormancy; strong dormancy restrict the part of each seed batch that germinate during autumn, and thus risk winter mortality, in Sweden.
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| 8. |
- Miao, Bai-Ge, et al.
(författare)
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Active pollination in a functionally dioecious Ficus species : An interplay between pollinator behaviour and floral morphology
- 2023
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Ingår i: Flora. - : Elsevier. - 0367-2530 .- 1618-0585. ; 302
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Tidskriftsartikel (refereegranskat)abstract
- Active pollination has evolved four times in brood site pollination mutualisms. When pollination is active, the pollinator's behaviour specifically evolves to ensure flower fertilisation. In functionally dioecious Ficus species, the male figs host pollinating wasp larvae, while wasps cannot breed in the female figs because the styles are longer than the wasp ovipositor. Here we investigate the dioecious Ficus hispida. We show that in male figs, every time the wasp has laid an egg into a pistillate flower, it removes one pollen grain from its pollen pockets and places it on the hypopygium. When the wasp inserts its ovipositor into the next flower, the pollen grain is deposited deep within the style. Each ovipositor insertion results in flower pollination and insect oviposition. Because of systematic pollination of the flowers into which the eggs are laid, the wasp larvae benefit from feeding on fertilised endosperm while no seed are produced. In female figs, after probing a flower, the wasp presents pollination behaviour only every five visits. However, if it does occur, this behaviour lasts longer than in male figs and results in the deposition of on average 10 pollen grains on the hypopygium. The exposed sticky papillae on the stigmatic surface collect pollen from the hypopygium and pollen tubes may grow to neighbouring stigmas, ensuring secondary dispersal and efficient ovule fertilisation. Overall, our study demonstrates that the floral morphology of male figs facilitates precise pollen deposition, beneficial for the wasp progeny, while the floral morphology of female figs compensates for wasp pollination behaviour that is not selected in those figs. We conclude that the morphology of the arena in which interactions with its pollinator are played out is the result of selection on the plant to maximize its male and female fitness. Incidentally, this morphology stabilises the mutualistic interaction.
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| 9. |
- Ollerton, Jeff, et al.
(författare)
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Diversity of Diptera families that pollinate Ceropegia (Apocynaceae) trap flowers: An update in light of new data and phylogenetic analyses
- 2017
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Ingår i: Flora. - : Elsevier BV. - 0367-2530 .- 1618-0585. ; 234, s. 233-244
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Tidskriftsartikel (refereegranskat)abstract
- Pollination by flies (Diptera) has been important to the diversification and ecology of the flowering plants, but is poorly understood in contrast to pollination by other groups such as bees, butterflies and birds. Within the Apocynaceae the genera Ceropegia and Riocreuxia temporarily trap flies, releasing them after a fixed, species-specific period of time, during which pollination and/or pollen removal occurs. This "trap flower" pollination system shows convergent evolution with unrelated species in other families and fascinated Stefan Vogel for much of his career, leading to ground-breaking work on floral function in Ceropegia (Apocynaceae). In this new study we extend the work of the latest broad analysis published by some of the authors (Ollerton et al., 2009 − Annals of Botany). This incorporates previously unpublished data from India and Africa, as well as recently published information, on the diversity of pollinators exploited by Ceropegia. The analyses are based on a more accurate phylogenetic understanding of the relationships between the major groups, and significantly widens the biogeographic scope of our understanding of fly pollination within Ceropegia. Information about the pollinators of 69 taxa (species, subspecies and natural varieties) of Ceropegia is now available. Twenty five families of Diptera are known to visit the flowers of Ceropegia, of which sixteen are confirmed as pollinators. Most taxa are pollinated by species from a single family. Overall, there were no major biogeographic differences in the types of Diptera that were used in particular regions, though some subtle differences were apparent. Likewise there were no differences between the two major clades of Ceropegia, but clear differences when comparing the range of Diptera exploited by Ceropegia with that of the stapeliads. This clade, one of the largest in the Asclepiadoideae, is a fascinating example of a species radiation driven by an apparently relatively uniform set of pollinators.
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| 10. |
- Patel, Vinay R., et al.
(författare)
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Cambial activity, annual rhythm of xylem production in relation to phenology and climatic factors and lignification pattern during xylogenesis in drum-stick tree (Moringa oleifera)
- 2014
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Ingår i: Flora. - : Elsevier. - 0367-2530 .- 1618-0585. ; 209:10, s. 556-566
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Tidskriftsartikel (refereegranskat)abstract
- The interrelationship among seasonality of cambium, wood formation, cell size variation, lignification, tree phenology and climatic factors has been examined in Moringa oleifera, a tropical evergreen tree. The vascular cambium in Moringa is a storied with a distinct seasonal variation in its structure due to dimensional changes in rays. Though cambium remains active throughout the year it is sensitive to water availability. Peak cambial cell division and rate of xylem differentiation are influenced by average rainfall during the monsoon period. Cambial cell division reaches higher up in the tree trunk when it is supporting a high number of branches and leaves. Statistical analysis of cell size variation and climate factors revealed that xylem cell development is greatly influenced by rainfall and rarely by temperature. Lengths of fusiform initials and vessel elements are positively correlated. The pattern of lignification during xylogenesis shows that the vessels are the first element to develop lignified walls and ray cells are the last elements to become lignified. Fiber cell walls show more syringyl lignin, while the cell walls of other xylem elements are characterized by relatively more guaiacyl lignin units.
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