Solitary Plants Research Articles

Adaptability and prospects for the use of introduced representatives of the genus Weigela in different climatic conditions

The use of highly decorative and beautifully flowering shrubs in urban green spaces, especially in sharply continental climatic conditions, is extremely important. In this regard, representatives of the genus Weigela are highly valued in the in different climatic conditions. The main indicators of eco-physiological adaptability of plants, such as intensity of transpiration and photosynthetic productivity, water deficiency and the total water content, quantity of the plastids, have been studied for the representatives of highly ornamental shrubs of the genus Weigela Thumb. The object of the research was the following representatives of the genus Weigela: W. praecox, W. coraeensis, W. floribunda, W. florida and W. florida ʺVariegataʺ, which were introduced into different climatic conditions in order to climate train and replenish the dendro-collections. Physiological research was conducted, during the vigorous vegetative period (May–June months). All the measurements were carried out within the 11:00–13:00 time period, in 9 repetitions (7–10 shoots were chosen for each sample). The nature of ecological adaptability of the studied species, along with the perspective of their application in the landscaping practices in different climatic zones was revealed. At the same time it was revealed that the studied species can be used not only as solitary plants (especially on the background of green lawns) but also in groups in long blooming gardens (with flowers with different colours and blooming phases) and in decorating rock gardens.

Spread of tree of heaven (Ailanthus altissima (Mill.) Swingle) in urban area

Three-of-heaven (Ailanthus altissima (Mill.) Swingle) is considered as one of the most invasive plant species worldwide in rural and urban environment. Although tree-of-heaven is commonly observed throughout the city of Osijek (Croatia), its prevalence and frequency has not been documented. This study has been conducted from May to September 2022 in the streets of Osijek to determine the distribution, abundance and competitive advantage of this species. A survey was performed by sampling randomly selected 20 quadrats in each city district, having together 140 phytocoenological records, and presence-absence of tree-of heaven was recorded in each plot. Where present at urban habitats, the number of threes were recorded and categorized approximately by the diameter at breast height (dbh). Habitats were distinguished as follows: alleys, abandoned private areas, public areas, ruderal sites, cracked walls and road edges. Risk assessment analysis were prepared by combining quantitative (number of trees per plots) and qualitative (four categories: biological characteristics and dispersal abilities, ecological amplitude and distribution, ecological impact, and difficulty to control) data. There was e recorded a total of 189 tree-of-heaven, occurring both as solitary plants or in developed stands. The habitat types with the highest rate of tree-of-heaven are abandoned private areas (34%) followed by public areas (31%). Out of the total, 55% of the recorded tree-of heaven are young individuals belonging to the very small and small diameter classes, and are mainly present on abandoned private and public areas. Ecological impact and biological characteristics are primary course of its landscape spread.

Plant-plant interaction by Aster leiophyllus affects herbivory by Sika deer, Cervus nippon.

Changes in leaf traits in response to plant-plant interactions affect feeding by insect herbivores. However, the effects of such changes on feeding by vertebrate herbivores remain unclear. We examined the effects of interactions of Aster leiophyllus collected in the field (growing with plants of the same species [aggregated] or with plants of different species [solitary]) or grown in pots (with another A. leiophyllus [intraspecific] or with Carex aphanolepis or Thalictrum baicalense [interspecific]) on the concentration of total phenolics in A. leiophyllus leaves and on sika deer (Cervus nippon) grazing preference in Japan. Deer were presented for 30s with the first A. leiophyllus leaf (from either aggregated plants or solitary plants) and then for 30s with the second leaf (solitary or aggregated, respectively). All of the deer presented first with a leaf from a solitary plant ate it, but when deer were presented first with a leaf from an aggregated plant, which had a higher concentration of total phenolics, 50% rejected or left it. About a third of the deer that had been presented first with a leaf from an aggregated plant subsequently rejected the leaf of a solitary plant. The leaves in the intraspecific interaction pot treatment had higher total phenolic concentration and were rejected more by deer than the leaves in the interspecific treatments. Plant-plant interactions affected deer preference, which was also influenced by learning. These results should improve our understanding of both plant grazing by deer and environmental management.

DECORATIVE HERBS, A GREEN SOLUTION FOR URBAN ARRANGEMENTS

Grasses or ornamental grasses are increasingly used in contemporany arrangements, both in the composition of lawns and as solitary plants, group, masifs or curbs. The present study was conducted to evaluate the behavior of some decorative grass species/cultivars: Carex morrowii ΄Snowline΄, Carex morowii ΄Ice Dance΄, Festuca glauca, Koeleria glauca, Miscanthus sinensism ΄Variegatus΄, Pennisetum alopecuroides ΄Hameln΄, Pennisetum setaceum ΄Rubrum΄, in different areas of Pitesti. Observations and determinations were made on: biological characteristics, ability to multiply, aesthetic qualities, growing and requirements, winter hardiness, pruning effects, correlated with the variation of everage annual temperatures (°C) and average annual rainfall (mm/month) in 2 year of reporting, 2019 and 2020. Ways have been proposed to use the ornamental grasses studied in the landscape arrangements and the importance of their incorporation in the green spaces, for ecosystem offers: restoring the ecological balance, capitalizing on natural resources and developing biodiversity.

Phytocenotic features of Calluna vulgaris (L.) Hill. in Ukrainian Polesie

Middle-aged pine and birch-pine forests of the Dicrano-Pinenion suballiance are the most common biotopes of Calluna vulgaris (L.) Hill. in Ukrainian Polesie. This species occurs mostly as solitary plants in forest phytocenoses; rarely its projective coverage can reach 40-45%. C. vulgaris has the highest constancy in phytocenoses of the Peucedano-Pinetum association in Right-bank Polesie. The forests of the Piceo-Vaccinienion uliginosi Seibert in Oberd. (ed.) 1992 suballiance and the Piceion excelsae Pawłowski et al. 1928 alliance are rare habitats of C. vulgaris; they occur only in Right-bank Polesie of Ukraine. Heathlands are rare ecosystems for Ukrainian Polesie, their vegetation is represented by plant communities of the Calluno-Ulicetea Br.-Bl. et Tx. ex Klika et Hadač 1944 and the Nardetea strictae Rivas Goday et Borja Carbonell in Rivas Goday et Mayor Lopez 1966 classes. They are forming in the significantly anthropogenically disrupted territories (e.g. areas after wildfires) or in the areas with intensive human activities, firstly in the military training areas. The phytocenoses of the Calluno-Genistetum pilosae R. Tx. 1937 association occur only in Right-bank Polesie and are the largest heathlands of Ukrainian Polesie in general. For example, in the Rivne region, their area is up to 20 km2. The area of heathlands, belonging to the Calluno-Nardetum strictae Hrync. 1959 association, does not exceed several hectares. The phytocenoses of the Scabioso canescentis-Genistetum Balcerk. et Brzeg 1993 association are represented with small plots in landscapes of pine forests and less frequently in mixed forests on upland terraces of Left-bank Polesie rivers. The characteristic feature of Calluna vulgaris spreading in Right-bank Polesie of Ukraine is its large participation (sometimes with the projective cover up to 80%) and high constancy (92,7%) in phytocenoses of oligotrophic bogs of the Ledo-Sphagnetum magellanici (Malc. 1929) Kästner et Flössner 1933 association. The populations of Calluna vulgaris, explored in the forest phytocenoses of the Cladonio-Pinetum Juraszek 1927 association on the territory of Ukrainian Polesie, are incomplete. Their age spectrum maximum falls on generative individuals. The “Right-bank” population of Calluna vulgaris are characterized by more active proliferation of plants and spreading on new territories. Aging processes dominate among the “left-bank” populations. Generally, environmental conditions of Ukrainian Right-bank Polesie are more favorable to Calluna vulgaris, than conditions of Left-bank Polesie.

Jumping the barrier: Does a glacier tongue affect species distribution along the elevation gradient in the subnival and nival belts? A case study on Mt. Kazbegi, Georgia, Central Great Caucasus Mountains

Glaciers are a prominent feature in high mountains and can affect plant distribution along the gradients. However, the possible effect of glaciers on plant community structure at landscape scale has been little studied. We asked: if a glacier tongue crosses a slope laterally and potentially blocks dispersal and migrations, how can this affect vegetation structure and species composition below and above this barrier? A suitable study system is offered by slopes on Mt. Kazbegi, where we established a transect through the subnival and nival belts. We sampled vegetation below and above the glacier tongue and conducted direct gradient analyses to reveal possible effects of the glacier on patterns of species distribution and vegetation structure such as the ratio of solitary plants in vegetation patches. The obtained results indicate that the glacier tongue in our study does not cause a ?vegetation switch? in the usual sense of this phrase. However, it might contribute to an abrupt change in the share of solitary plants, as well as to a very rapid decline of plant abundance and species numbers above the glacier.

Benefits for nurse and facilitated plants emerge when interactions are considered along the entire life-span

The structure of plant communities is often influenced by facilitative interactions where ‘facilitated’ plants benefit from growing associated with ‘nurse’ plants. Facilitation has been mostly studied from the facilitated plant’s perspective, and bidirectional effects between nurse and facilitated plants have received less attention. We hypothesized that reciprocal benefits in plant-plant interactions may emerge when interactions are considered along the life-span of the plants involved. Over one spring, we selected five species with similar life-form and growth strategy, and using a full factorial design, we compared different fitness components along the plants’ life-span (seedling establishment, juvenile growth and reproductive investment in adult plants). We compared: a) plants growing in solitary stands and associated with other plants in vegetation patches; and b) plants that originally functioned as nurse plant (the largest plant of the vegetation patch) and as facilitated (not the largest plant of the vegetation patch). At an early developmental stage, facilitated plants growing in vegetation patches displayed higher seedling establishment and juvenile growth compared to solitary conspecific plants. At a later developmental stage, nurse plants in vegetation patches experienced higher reproductive investment (measured as flower production relative to plant size) compared to solitary plants, while the originally facilitated plants showed similar reproductive investment compared to their solitary pair of similar size. Facilitation is likely a complex interaction in which reciprocal benefits for both facilitated and nurse plants can be detected when interactions are considered along the plants’ life-span. Our results suggest that mutual benefits in plant-plant interactions could be important to sustain diversity in plant communities, but they appeared overlooked and deserve further attention.

Nowe stanowisko Lycopodiella inundata (Lycopodiaceae) w Kotlinie Biskupiego Boru (Wyżyna Śląska)

Lycopodiella inundata is a rare and protected pteridophyte species in Poland. It usually occurs in oligotrophic wetlands, mainly in transitional moors (Rhynchosporetum albae). Lycopodiella inundata has rarely been found at natural sites recently, probably due to unfavorable environmental changes, but appears more and more often at sites created by human activity, such as sand pits, gravel pits and the banks of fish ponds. In 2014 a new site of L. inundata was found in the eastern part of the Szczakowa sand pit (19°25′35″E, 50°15′18″N). In this area, L. inundata grows well and occurs abundantly in small conspecific patches, aggregations, or as solitary plants. The main threats to this site are expansion of forest and shrub vegetation, reed expansion, changes in groundwater level, and drainage of the area.

Journal entries, maps, and photos help ecologists reconstruct ecosystems of the past

Ilka Feller has a penchant for mangrove hunting. Since the early 2000s, Feller, an ecologist at the Smithsonian Environmental Research Center, has periodically gone road-tripping in search of the northernmost mangrove tree in Florida. The red mangrove, Rhizophora mangle , has draping roots that hold fast in the tide. But all three of Florida’s mangrove species anchor themselves and whole ecosystems—protecting the shoreline from erosion, forming nurseries for fish, and sequestering carbon. Ecologist Ilka Feller used archival records to investigate whether mangroves in Florida, like these in Indian River Lagoon, are expanding into new territories or returning to a historical range. Image credit: Ilka Feller. Globally, mangroves are threatened by coastal development and shrimp farming. “More than half of the world’s mangroves have already been destroyed,” says Feller. Yet in Florida, Feller kept finding new mangroves farther and farther north, “solitary plants that are out there in this forever saltmarsh.” As part of a 2014 study, Feller’s then postdoc, Kyle Cavanaugh, analyzed satellite images taken from 1984 to 2011 and saw that mangroves were indeed advancing northward (1). The spread was associated with a reduced frequency of extreme cold events. Climate change, it seemed, was replacing marshland, an important temperate ecosystem, with mangroves, an important subtropical and tropical one. But had they really revealed a trend pointing in one direction, or was the recent expansion of mangroves part of a continual cycle of mangrove and saltmarsh replacing one another? Feller needed more than just conventional scientific data to find out. So she dug into Florida’s past using tools more typical of historians. She found mangroves mentioned in the texts of famed naturalist John Muir, uncovered data in tourist photos, and parsed the writings of war surgeons and beekeepers. Feller and a growing group of ecologists are piecing together historical records …

The role of biomass allocation between lamina and petioles in a game of light competition in a dense stand of an annual plant.

Models of plant three-dimensional (3-D) architecture have been used to find optimal morphological characteristics for light capture or carbon assimilation of a solitary plant. However, optimality theory is not necessarily useful to predict the advantageous strategy of an individual in dense stands, where light capture of an individual is influenced not only by its architecture but also by the architecture of its neighbours. Here, we analysed optimal and evolutionarily stable biomass allocation between the lamina and petiole (evolutionarily stable strategy; ESS) under various neighbour conditions using a 3-D simulation model based on the game theory. We obtained 3-D information of every leaf of actual Xanthium canadense plants grown in a dense stand using a ruler and a protractor. We calculated light capture and carbon assimilation of an individual plant when it stands alone and when it is surrounded by neighbours in the stand. We considered three trade-offs in petiole length and lamina area: biomass allocation, biomechanical constraints and photosynthesis. Optimal and evolutionarily stable biomass allocation between petiole and lamina were calculated under various neighbour conditions. Optimal petiole length varied depending on the presence of neighbours and on the architecture of neighbours. The evolutionarily stable petiole length of plants in the stand tended to be longer than the optimal length of solitary plants. The mean of evolutionarily stable petiole length in the stand was similar to the real one. Trade-offs of biomechanical constraint and photosynthesis had minor effects on optimal and evolutionarily stable petiole length. Actual plants realize evolutionarily stable architecture in dense stands. Interestingly, there were multiple evolutionarily stable petiole lengths even in one stand, suggesting that plants with different architectures can coexist across plant communities.

The function of the floral corona in the pollination of a Mediterranean style dimorphic daffodil.

Narcissus papyraceus is a style dimorphic species with two floral forms, with anthers at similar height and stigmas above (long-styled L) and below (short-styled S) the anther level. The species is self-incompatible, but intra- and inter-morph compatible. Populations are either dimorphic (including both morphs) in the region of the Strait of Gibraltar, or L-monomorphic (with only L plants) in the inland of the Iberian Peninsula. This variation correlates with the most common floral visitors, being primarily long-tongued and short-tongued pollinators, respectively, a rare condition in Mediterranean plants. The maintenance of S-flowers relies on long-tongued insects, as only those deliver pollen to short-styled stigmas. Narcissus flowers present a long and narrow tube, at the bottom of which nectar accumulates, and a floral corona, which has been proposed as an important trait for the attraction of pollinators. Here we tested the importance of the corona on pollination of L and S flowers. We described UV reflectance patterns of the corona and tepals, and characterised VOCs in intact flowers and flowers with trimmed coronas. We also conducted a field experiment in the dimorphic and monomorphic region to estimate the importance of corona removal on seed production in stands with solitary plants and in groups to control for compatible pollen limitation. Reflectance was higher in the tepals than the corona, although both traits presented a reflectance peak around 450nm wavelength. L- and S-flowers produced similar volatiles, regardless of the manipulation of the corona. Across dimorphic and monomorphic regions, S-flowers with the corona removed suffered a reduction in seed production of ca. 50%, while seed production remained similar in L flowers both with the corona intact and removed. Plants in solitary stands suffered a strong reduction in seed production, which was more pronounced in the monomorphic region. Our results suggest that the corona in Narcissus is more important for the pollination of S-flowers, which generally have lower seed production compared to L-flowers. Taken together, these results suggest that the floral corona indirectly plays an important role for maintenance of the polymorphism.

Does a plant detect its neighbor if it is kin or stranger? Evidence from a common garden experiment

Unlike vagile organisms, plants perform a wide range of phenotypic responses to cope with environmental stresses. A special case of interaction with external factors is the ability of plants to recognize genetic relatedness of neighbour plants, actually well known as kin recognition. The present work aimed to provide a valuable contribution to the field of kin recognition in plants through a common garden experiment. To avoid bias involved in pot experiments, we perform an experiment in unconstrained root growth conditions comparing the development of coupled kin, non-kin and solitary plants of Xanthium italicum. Biometrics of plants with different genetic relatedness were measured, then architecture and competitive interaction were assessed using the relative interaction index (RII) for above and belowground portions of plants. X. italicum showed different allocation depending on the neighbourhood. Root biomass was declined in plants growing with kin compared to non-kin coupled plants, while plants coupled with kin allocated more shoot than roots compared to solitary plants. RII explains phenotypic response of decreased competition in roots rather than in shoots. Despite high values of RII for the aboveground portion, the architectural analysis of shoot, number, angle and length of branches and roots reveals dramatic but indistinctive change in the structure of plants growing near kin or non kin compared to a solitary plant. These results confirm phenotypic responses of kin recognition in unconstrained environment.

Oviposition site selection of a threatened moth Eriogaster catax (Lepidoptera: Lasiocampidae) in agricultural landscape\u2014implications for its conservation

Shrubby field margins and hedgerows play an important role for many species of flora and fauna in agro-ecosystems, including those which are rare or endangered. A characteristic species of these semi-natural habitats in agricultural landscape is the Eastern eggar, Eriogaster catax (Linnaeus, 1758): a moth species threatened in many European countries. In this study we investigated the oviposition preferences of E. catax at host plant level in agricultural landscape in south-western Poland, near of the northern limit of the species distribution in Europe. In total we surveyed 796 host plants. Altogether we found 439 eggs batches or caterpillar webs of E. catax on 373 occupied plants. Most of them (92.3%) were on blackthorn Prunus spinosa, which was preferred host plant next to pear Pyrus spp. However, the most important predictor of the presence of egg batches were microclimatic conditions. We recorded that females preferred host plants exposed to direct sunlight and with south and west-facing slopes for oviposition and avoided those inside of the dense shrub canopy. Eggs were laid more often on the trunk and on the upper half of the host plant, however there was a significant difference in vertical and horizontal position of egg batches in relation to the position of the plant. Inside of the shrub canopy, eggs were laid in higher parts of host plant and closer to the trunk, than at the edge and on solitary plants. Based on our observations the management strategies for the habitats of the species are proposed and discussed.

From facilitative to competitive interaction between Larrea tridentata and Cylindropuntia leptocaulis in the southern Chihuahuan Desert

AbstractQuestionCan the co‐existence of the cactus and the shrub in the community be driven by a cyclic succession mechanism?LocationMapimí Biosphere Reserve (southern Chihuahuan Desert). The vegetation is scrub, dominated by Larrea tridentata.MethodsInterspecific spatial association between adult L. tridentata and differently sized Cylindropuntia leptocaulis plants was analysed using Ripley′s K function, exploring the hypothesis that facilitation causes differential recruitment of cactus below the shrub and a subsequent interspecific association, the intensity of which declines with the cactus size due to competitive elimination of the shrub. Competition for water among adult plants was investigated by irrigating solitary and associated plants of both species. The proportion of vigorous (measured by the percentage of dead branches) and dead L. tridentata plants associated with adult cacti was compared to that of solitary L. tridentata plants, testing the hypothesis that competition among associated adults reduces the vigour and increases the proportion of dead shrubs, relative to that of solitary plants.ResultsIn 14 out of 16 spatial analyses (four cactus sizes in four plots), C. leptocaulis was found to clump around the L. tridentata adults. Larrea tridentata suffered the effects of interspecific competition for water, but these diminished with increased water provision. In contrast, C. leptocaulis was unaffected by interspecific competition for water. The proportion of vigorous shrubs was higher in solitary than in associated individuals; however, the proportion of dead shrubs was lower in associated than in solitary individuals.ConclusionThe irrigation experiment and the proportion of dead branches suggest interspecific competition. However, spatial association of the shrubs with every cactus size and the proportion of dead shrubs associated with the cacti both suggest that replacement of the shrub by the cactus is an infrequent event. Cyclic succession therefore appears to be the exception rather than the rule, and does not account for the co‐existence of the species in the community. The possible scenarios in which cyclic succession may occur are discussed.

Branching, nitrogen distribution, and carbon gain in solitary plants of an annual herb, Xanthium canadense

The theory of optimal nitrogen (N) distribution predicts that the carbon gain of plants will be maximised when leaves of higher irradiance have higher N content per area (N area). Most previous studies have examined optimal N distribution without explicitly considering the branching status of plants. I investigated light environment, N distribution and photosynthetic traits of individual leaves of an herbaceous species, Xanthium canadense. X. canadense was grown solitary under high (HN) and low nutrients (LN). Light availability, leaf mass per unit area and N area were measured for all leaves within plants. Daily photosynthesis of the plants of actual N distribution was compared with those of optimal and constant N distribution. Branch production was facilitated in HN but not in LN plants. N area was correlated more with leaf order than with leaf light environment. Although N was more limited and the light environment was less heterogeneous within crowns in LN than in HN plants, leaf N distribution was closer to optimal in the latter. These results suggest that leaf N distribution was not optimised in solitary plants of X. canadense. Because this species often regenerates in a dense stand, leaf N distribution might be selected to maximise carbon gain only in such a stand. Leaf N distribution might thus be constrained by the regeneration strategy of the species.

A putativeOreocereusxEchinopsishybrid from southern Bolivia

Solitary plants of the putative intergeneric cross Oreocereus celsianus × Echinopsis tarijensis were found on two independent occasions in the same general region of S Bolivia (Dept. Potosí). The plants are described and illustrated. They are intermediate in general appearance and flower characters between the supposed parents, and appear to be sterile. The importance of intergeneric and interspecific crosses in the evolution of Cactaceae is briefly discussed, and the relative ease with which intergeneric hybrids can be artificially obtained in cultivation is contrasted with the apparent rarity of naturally occurring intergeneric hybrids. Based on available evidence, the impact of natural intergeneric hybridization on cactus evolution appears to be limited.

Belowground neighbor perception in Arabidopsis thaliana studied by transcriptome analysis: roots of Hieracium pilosella cause biotic stress.

Root-root interactions are much more sophisticated than previously thought, yet the mechanisms of belowground neighbor perception remain largely obscure. Genome-wide transcriptome analyses allow detailed insight into plant reactions to environmental cues. A root interaction trial was set up to explore both morphological and whole genome transcriptional responses in roots of Arabidopsis thaliana in the presence or absence of an inferior competitor, Hieracium pilosella. Neighbor perception was indicated by Arabidopsis roots predominantly growing away from the neighbor (segregation), while solitary plants placed more roots toward the middle of the pot. Total biomass remained unaffected. Database comparisons in transcriptome analysis revealed considerable similarity between Arabidopsis root reactions to neighbors and reactions to pathogens. Detailed analyses of the functional category “biotic stress” using MapMan tools found the sub-category “pathogenesis-related proteins” highly significantly induced. A comparison to a study on intraspecific competition brought forward a core of genes consistently involved in reactions to neighbor roots. We conclude that beyond resource depletion roots perceive neighboring roots or their associated microorganisms by a relatively uniform mechanism that involves the strong induction of pathogenesis-related proteins. In an ecological context the findings reveal that belowground neighbor detection may occur independently of resource depletion, allowing for a time advantage for the root to prepare for potential interactions.

Growth and nitrogen use in Xanthium canadense grown in an open or in a dense stand

Plants develop branches profusely when grown solitarily, while less so when grown in a dense stand. Such changes in architecture are associated with changes in dry mass allocation and nitrogen use. Here, we studied what traits in plant growth and nitrogen use were influenced by different light climates in the stand. Annual plants (Xanthium canadense) were grown solitarily or in a dense stand. Dry mass growth was analyzed as the product of the net assimilation rate (NAR) and leaf area (LA). Nitrogen use efficiency (NUE) was analyzed as the product of nitrogen productivity (NP) and the mean residence time (MRT) of nitrogen. These growth variables were further factorized into their components. Solitary plants maintained a high NAR, whereas plants in the dense stand decreased the NAR due to mutual shading. Plants in the dense stand developed a larger LA with a higher specific leaf area than solitary plants. Solitary plants had higher NUE due to higher NP. A temporal increase in NUE was attributed to the increase in MRT of nitrogen. Light climate was different between solitary and dense-stand plants, but they took up a comparable amount of nitrogen and used it differently in response to the given light climate. NUE was thus demonstrated to be a useful tool for analyzing the mechanism leading to different N use in plant growth.

Causes of Low Fruit and Seed Set in Bird-Pollinated Anagyris foetida (Leguminosae): Pollen Limitation and Other Extrinsic Factors

We studied the extrinsic factors behind the low number of offspring in two populations of Anagyris foetida, a bird-pollinated leguminous shrub of the Mediterranean region. Fruit initiation was pollen limited, but fruit maturation was not. This limiting effect varied between flowering seasons and between populations, and also within a given phenological stage. In the first season, the early flowers had the lowest fruit set, while in the second season fruit set was highest in these early flowers. This was possibly related to the pollination environment. Seed initiation (fertilized ovules) increased following pollen supplementation, but this was not translated into a significant increase in either the number of seeds per fruit, or seed mass. This indicates that seed initiation is pollen limited but that other factors (e.g., resource availability) are involved in seed maturation. Abiotic factors such as excess humidity during flowering were responsible for the loss of inflorescences, especially in one of the two populations. In this population, the prevailing wind in autumn-winter was less effective in drying the flowers when there was excess humidity. Also, significantly fewer inflorescences were lost from solitary plants than from clustered plants, probably reflecting the beneficial action of the wind and the greater light levels during flowering. Of the biotic factors analyzed, sheep predation was the most important, being worse in drought years. This predation, by affecting population density, could modify the plant-pollinator interaction and severely reduce the plant’s breeding success because of its pollen limitation.

Architecture and growth of an annual plant Chenopodium album in different light climates

AbstractLight climates strongly influence plant architecture and mass allocation. Using the metamer concept, we quantitatively described branching architecture and growth of Chenopodium album plants grown solitarily or in a dense stand. Metamer is a unit of plant construction that is composed of an internode and the upper node with a leaf and a subtended axillary bud. The number of metamers on the main‐axis stem increased with plant growth, but did not differ between solitary and dense‐stand plants. Solitary plants had shorter thicker internodes with branches larger in size and number than the plant in the dense stand. Leaf area on the main stem was not different. Larger leaf area in solitary plants was due to a larger number of leaves on branches. Leaf mass per area (LMA) was higher in solitary plants. It did not significantly differ between the main axis and branches in solitary plants, whereas in the dense stand it was smaller on branches. Dry mass was allocated most to leaves in solitary plants and to stems in the dense stand in vegetative growth. Reproductive allocation was not significantly different. Branch/main stem mass ratio was higher in solitary than dense‐stand plants, and leaf/stem mass ratio higher in branches than in the main axis. Nitrogen use efficiency (NUE) (dry mass growth per unit N uptake) was higher and light use efficiency (LUE) (dry mass growth per unit light interception) was lower in the plant grown solitarily than in the dense stand.