Inflorescence Size Research Articles

Study on the inflorescences of Arundo donax L. clones sampled in Italy

The giant reed, Arundo donax L. (Poaceae), is a perennial plant species widespread almost all over the world. It is not only considered as an invasive plant, but it also represents one of the most promising energy crops because of its vegetative vigor, high yields, and the low input required for its cultivation. Giant reed reproduces itself only agamically through rhizomes and cane fragments, usually transported by water or through human action. In this work, inflorescences from a collection of clones sampled all over Italy were studied. The results confirmed the sterility of A. donax: no pollen was observed and no seeds were found despite the large size of the inflorescences. Furthermore, 83 clones of the collection were characterized for their inflorescence size and flowering time. We found, for the first time, a significant correlation between the geographical coordinates (latitude) of sampling and the flowering time (r = −0.902 and r = −0.836, respectively at the 4th and at the 5th year after clones transplantation in our experimental farm). A survey of 15 clones, chosen to represent all the Italian territory, was also studied from the genetic point of view using 10 simple sequence repeats molecular markers, to further explore the genetic variability of this species in Italy, and to verify the presence of correlations with the phenotypic differences observed. Although PCA (Principal Component Analysis), AMOVA (Analysis of Molecular Variance), and the calculation of the average pairwise relatedness of populations analysis suggested the presence of three distinct clusters, no correlation was observed between genetic data and inflorescences’ phenotypic data.

Cytoembryological and morphometric characteristics of some Armenian grape cultivars

Introduction: The conservation and phenotypic characterization of Armenian grapevine gene pool is the basis for its application in future breeding programs. The cytoembryological analysis and the phenotypic characterization of grapevine male and female gametophytes and of early developed embryos could improve the understanding of genetic mechanisms involved at different stages of reproductive development (PRATT 1971, MULLINS et al. 1992, FERNANDES et al. 2007, NEBISH 2012). Flowering and berry set are important stages of grapevine development, and they could also affect the yield quantity and quality (LONGBOTTOM 2007). Grapevine cultivars are highly heterozygous. They show a large variation in inflorescence size, berry size, shape, weight and colour depending on genotypes and environmental conditions (THIS et al. 2006, CARMONA et al. 2008). The aim of our study was the phenotypic characterization of some Armenian grape cultivars by cytoembryological and carpological analysis. Material and Methods: Ten accessions of Armenian grapevines were analysed including: 5 Vitis vinifera L. cultivars (authochthonous 'Mskhali', 'Garan dmak' and clone of 'Ararati' cultivars, 'Tokun' open pollination of 'Spitak Arakseni', 'Muscat haykakan' open pollination of 'Muscat cherniy'); 3 intraspecific hyvrids ('Berkanush', 'Parvana' and 'Erebuni') and 2 V. vinifera x V. amurensis interspecific hybrids ('Charentsi' and 'Meghrabuyr'). All the accessions were grown in the same collection of the Scientific Center of Viticulture, Fruit-Growing and Wine-Making (Merdzavan, Armenia). In 2013 flowers for cyto-embryological analysis of microand macro-gametophyte, and ripe berries for morphometric studies were collected. For estimation of pollen fertility the acetocarmine staining method have been used. Pollen sterility data were obtained based on the analysis of about 5000 pollen grains for each accession. Concerning cytoembryological investigations, fixation in FAA fixative (formaldehyde – acetic acid – ethanol) were applied. Material was then stained by Mayer's hematoxylin and eosin (HE 1997) by the ImageJ software. Statistical analysis of data was carried out using Student's t-test and 5 % probability was considered significant.

Plant reproductive traits mediate tritrophic feedback effects within an obligate brood-site pollination mutualism.

Plants, herbivores and parasitoids affect each other directly and indirectly; however, feedback effects mediated by host plant traits have rarely been demonstrated in these tritrophic interactions. Brood-site pollination mutualisms (e.g. those involving figs and fig wasps) represent specialised tritrophic communities where the progeny of mutualistic pollinators and of non-mutualistic gallers (both herbivores) together with that of their parasitoids develop within enclosed inflorescences called syconia (hence termed brood-sites or microcosms). Plant reproductive phenology (which affects temporal brood-site availability) and inflorescence size (representing brood-site size) are plant traits that could affect reproductive resources, and hence relationships between trees, pollinators and non-pollinating wasps. Analysing wasp and seed contents of syconia, we examined direct, indirect, trophic and non-trophic relationships within the interaction web of the fig-fig wasp community of Ficus racemosa in the context of brood site size and availability. We demonstrate that in addition to direct resource competition and predator-prey (host-parasitoid) interactions, these communities display exploitative or apparent competition and trait-mediated indirect interactions. Inflorescence size and plant reproductive phenology impacted plant-herbivore and plant-parasitoid associations. These plant traits also influenced herbivore-herbivore and herbivore-parasitoid relationships via indirect effects. Most importantly, we found a reciprocal effect between within-tree reproductive asynchrony and fig wasp progeny abundances per syconium that drives a positive feedback cycle within the system. The impact of a multitrophic feedback cycle within a community built around a mutualistic core highlights the need for a holistic view of plant-herbivore-parasitoid interactions in the community ecology of mutualisms.

A TAXONOMIC REVIEW AND A NEW SPECIES OF THE SOUTH AMERICAN WOODY GENUS AMBURANA (LEGUMINOSAE, PAPILIONOIDEAE)<br />

A taxonomic revision of the South American genus Amburana comprised of three species is presented, including the new species A. erythrosperma which is described and illustrated. Amburana cearensis occurs widely in Argentina, Bolivia, Brazil and Paraguay. Amburana acreana occurs in the Bolivian, Brazilian and Peruvian Amazon. Amburana erythrosperma is endemic to the southern Chapada Diamantina, Bahia, Brazil. The species are distinguished by the color of the stem, the number per leaf and shape of leaflets, the size of inflorescence, color and size of the standard petal, fruit with endocarp developed to form a papery wing surrounding the seed or this lacking, and color of seed. A key to the species is provided together with descriptions, taxonomic comments, geographical distribution maps and illustrations for each. Lectotypes for A. acreana and A. cearensis are designated.

Inter and intra-specific genetic differentiation for agro-economical traits in Plantago germplasm

Genetic differentiation and divergence among sixty indigenous and exotic collections comprising three species of isabgol was quantified for fourteen economic traits. Highly significant differences indicated existence of considerable genetic variability, as evident from the tremendous variation in shape and size of inflorescence. Considerable differences in economic traits, growth and other parameters were also noted. The germplasms could be grouped into nine clusters and enormous diversity among accessions were indicated by wide range of D2 values (0.896–41,358.16). The cluster pattern was also confirmed by canonical analysis. Husk yield/plot was the highest contributor (37.79 %), followed by inflorescence husk yield (26.80%), whereas, peduncle length was the least contributor (2.14%) to seed yield. Five accessions each were identified to be the best in seed yield, husk yield, swelling factor and long panicle length. Three accessions can exploited for commercial cultivation to fulfill industrial use/demands.

Introduced elk alter traits of a native plant and its plant-associated arthropod community

Introduced species are known to have large impacts on native ecosystems, by extirpating species, altering species interactions and changing community composition. The mechanisms by which introduced species impact native communities often include both direct and indirect effects. Here, we combined observational field surveys, an exclosure experiment, network analysis and structural equation modeling to examine the direct and indirect effects of an introduced species on native communities. Specifically, we investigated how introduced elk indirectly impact the composition and co-occurrence patterns within a community of plant-associated arthropods by directly altering the phenotype of a native plant, Solidago velutina. Surveying the arthropods associated with the plant's inflorescence, two main patterns emerged. i) Using field observations across 500 km2 and an exclosure experiment, S. velutina growing in the presence of elk had 67–90% fewer flowering ramets, 15–85% lower percentage of flowering ramets, 33–45% fewer florets per inflorescence and 25–45% lower sexual ramet biomass. ii) Using the same exclosures, the arthropod community on S. velutina in the presence of elk, had 45% fewer species, a 70% reduction in abundance and a significant change to the species composition and co-occurrence network structure. The results from the network analysis suggested that introduced species' impacts on communities can be more than changes in richness or abundance, but include changes to species interactions. Structural equation modeling showed that elk caused a decrease in inflorescence size of S. velutina, which affected the arthropod community, suggesting that communities can change without extirpation of their host plant species. These results highlight the importance of changing intraspecific variation as a mechanism by which invasive species alter community composition and species interactions.

Effect of paclobutrazol in potted plants of four cultivars of Dianthus barbatus × chinensis

Summary Dianthus barbatus × chinensis is a perennial herb derived from the interspecific cross between Sweet Williams (D. barbatus L.) and China pink (D. chinensis L.). At present cultivated as a cut flower, it could be potential as a flowering potted plant, but height control should be performed. In this study, the possibility to reduce plant height by the use of paclobutrazol (triazole; PBZ) was investigated in four cultivars. In addition, the effect of PBZ on flowering (inflorescence number and size, and flowering time) and on leaf colour was evaluated. Two experiments were carried out in different seasons (corresponding to autumn potting and summer potting, respectively) and PBZ was applied as a substrate drench at different dosages: 0.5, 1, and 2 mg per pot for autumn-potted plants; 0.25, 0.5, and 1 mg per pot for summer-potted plants. Paclobutrazol resulted to be effective in controlling plant height in all the studied cultivars without producing any toxicity symptoms. Neither effect of PBZ on number and size of inflorescences, nor on flowering time was observed. On the contrary, PBZ enhanced leaf colour.

An improved method for the visualization of conductive vessels in Arabidopsis thaliana inflorescence stems.

Dye perfusion is commonly used for the identification of conductive elements important for the study of xylem development as well as precise hydraulic estimations. The tiny size of inflorescence stems, the small amount of vessels in close arrangement, and high hydraulic resistivity delimit the use of the method for quantification of the water conductivity of Arabidopsis thaliana, one of the recently most extensively used plant models. Here, we present an extensive adjustment to the method in order to reliably identify individual functional (conductive) vessels. Segments of inflorescence stems were sealed in silicone tubes to prevent damage and perfused with a dye solution. Our results showed that dyes often used for staining functional xylem elements (safranin, fuchsine, toluidine blue) failed with Arabidopsis. In contrast, Fluorescent Brightener 28 dye solution perfused through segments stained secondary cell walls of functional vessels, which were clearly distinguishable in native cross sections. When compared to identification based on the degree of development of secondary cell walls, identification with the help of dye perfusion revealed a significantly lower number of functional vessels and values of theoretical hydraulic conductivity. We found that lignified but not yet functional vessels form a substantial portion of the xylem in apical and basal segments of Arabidopsis and, thus, significantly affect the analyzed functional parameters of xylem. The presented methodology enables reliable identification of individual functional vessels, allowing thus estimations of hydraulic conductivities to be improved, size distributions and vessel diameters to be refined, and data variability generally to be reduced.

Variation of nectar production in relation to plant characteristics in protandrous Aconitum gymnandrum

Floral nectar plays a vital role in plant reproductive success by attracting pollinators. Nectar traits of a flower can depend directly on plant characteristics other than environmental factors and exhibit extensive flower- and plant-level variations. Studies on nectar traits frequently focused on intraplant variation for dichogamous plants, but few have paid attention to both intra- and interplant nectar variations in relation to plant characteristics. Revealing within- and among-plant variation and its relative magnitude is important for our understanding of how pollinator-mediated selection can act on nectar traits and evolution of nectar traits. Through investigating protandrous Aconitum gymnandrum populations at the Alpine Meadows and Wetland Ecosystems Research Station of Lanzhou University, we examined the relationships between nectar production per flower and plant characteristics (e.g. flower position within inflorescences, floral sexual phases, flowering time, inflorescence size and floral attractive traits). A. gymnandrum exhibited a declining gradient in the nectar volume along inflorescences, with more nectar in basal flowers than distal ones. Protandrous flowers of A. gymnandrum did not show gender-biased nectar production while the nectar volume varied with different stages of floral sexual phases. The significant correlation between the first flowering date of individuals and the mean nectar volume per flower was positive in 2013, but became negative in 2014, suggesting complex effects of biotic and abiotic factors. The mean nectar volume per flower was not related to inflorescence size (the number of total flowers per plant). Furthermore, nectar production was weakly associated with floral attractive traits (the petal width and the galea height), even if the effect of flowering time of individuals was removed, suggesting that the honesty of floral traits as signals of nectar reward for pollinators is not stable in this species.

Pollination system and the effect of inflorescence size on fruit set in the deceptive orchid Cephalanthera falcata.

Larger inflorescences in reward-producing plants can benefit plants by increasing both pollinator attraction and the duration of visits by individual pollinators. However, ultimately, inflorescence size is determined by the balance between the benefits of large inflorescences and the increased cost of geitonogamy. At present, little is known about the relationship between inflorescence size and fecundity in deceptive plants. Given that pollinators are likely to leave inflorescences lacking rewards quickly, it seems unlikely that longer pollinator visits and the risk of geitonogamy would be strong selective pressures in these species, which indicates that pollinator attraction might be the most important factor influencing their inflorescence size. Here we examined the pollination ecology of the deceptive orchid Cephalanthera falcata in order to clarify the effects of inflorescence size on the fruit set of this non-rewarding species. Field observations of the floral visitors showed that C. falcata is pollinated by the andrenid bee Andrena aburana, whilst pollination experiments demonstrated that this orchid species is neither autogamous nor apogamous, but is strongly pollinator dependent. Three consecutive years of field observations revealed that fruit set was positively correlated with the number of flowers per inflorescence. These results provide strong evidence that the nectarless orchid C. falcata benefits from producing larger inflorescences that attract a greater number of innate pollinators. Large inflorescences may have a greater positive effect on fruit set in deceptive plants because a growing number of studies suggest that fruit set in reward-producing plants is usually unaffected by display size.

Large size and high light do not lower the cost of reproduction for the Neotropical herb Goeppertia marantifolia

• Sexual reproduction is often associated with a cost in terms of reduced survival, growth, or future reproduction. It has been proposed that plant size and the environment (availability of key resources) can sometimes lower or even nullify the cost of reproduction.• We address this issue experimentally with the Neotropical herb Goeppertia marantifolia, by manipulating sexual reproductive effort and measuring the demographic performance of plants and of their clonal offspring, in the context of natural variation in light availability.• Plants in the high-reproductive-effort treatment grew less between seasons but did not differ in their probability of flowering the second season or in inflorescence size compared with plants in the low-effort treatment. Reproductive effort of parent plants influenced the leaf area of their clonal offspring. Plants that invested less in sexual reproduction produced clonal offspring that were initially larger than those produced by plants that invested more in reproduction. The magnitude of this effect was greater in parent plants that received two seasons of the manipulated reproductive effort than in those that received a single season. The trade-off between reproductive modes dampened with time, leading to smaller differences in clonal offspring leaf area between treatments over time.• We found evidence of a cost of reproduction and trade-offs between reproductive modes, although the magnitude of these costs was small. However, we found no evidence of lower costs of reproduction for larger plants or for plants in higher-light environments over our 2-yr study period.

Orchid-pollinator interactions and potential vulnerability to biological invasion.

Mutualistic relationships between plants and their pollinators have played a major role in the evolution of biodiversity. While the vulnerability of these relationships to environmental change is a major concern, studies often lack a framework for predicting impacts from emerging threats (e.g. biological invasions). The objective of this study was to determine the reliance of Platanthera ciliaris (orange-fringed orchid) on Papilio palamedes (Palamedes swallowtail butterfly) for pollination and the relative availability of alternative pollinators. Recent declines of P. palamedes larval host plants due to laurel wilt disease (LWD) could endanger P. ciliaris populations that rely heavily on this butterfly for pollination. We monitored pollinator visitation and fruit set and measured nectar spur lengths of P. ciliaris flowers and proboscis lengths of its floral visitors in Jackson County, MS, USA. Papilio palamedes was the primary visitor with minimal visitation by Phoebis sennae (cloudless sulfur butterfly). Lengths of P. ciliaris nectar spurs were similar to proboscis lengths of both pollinator species. Fruit set was moderate with access to pollinators (55 ± 10.8 %), yet failed (0 %) when pollinators were excluded. Visitation increased with inflorescence size, but there was no such pattern in fruit set, indicating that fruit set was not limited by pollinator visitation within the range of visitation rates we observed. Our results are supported by historical data that suggest P. palamedes and P. sennae are important pollinators of P. ciliaris. Although P. sennae may provide supplemental pollination service, this is likely constrained by habitat preferences that do not always overlap with those of P. cilaris. Observed declines of P. palamedes due to LWD could severely limit the reproductive success and persistence of P. ciliaris and similar orchid species populations. This empirical-based prediction is among the first to document exotic forest pests and pathogens as an indirect threat to plant-pollinator interactions.

Protein hydrolysate as a component of salinized soil in the cultivation of Ageratum houstonianum Mill. (Asteraceae)

The aim of the present study was to evaluate the possibility of using a protein hydrolysate, Hemozym N-K 4.5-6, as a component of salinized soil in the cultivation of flossflower (<em>Ageratum houstonianum</em> Mill., Asteraceae). The experiment was focused on the yield and decorative value of <em>A. houstonianum</em>, grown under different concentrations of NaCl and/or Hemozym. <em>Ageratum houstonianum</em> plants were grown in the soil under different NaCl salinity (EC: 0.28 – as control or 3.25 dS m<sup>−1</sup> – salt stress) or/and Hemozym dose (0, 0.07 or 0.14 ml kg<sup>−1</sup>). The results of the experiment imply that <em>A. houstonianum</em> is sensitive to salinity. The application of Hemozym to both unsalinized and salinized soils caused an increase in the yield of the plant organs (roots, stems, leaves, and inflorescence), the number of leaves, and the chlorophyll content without significant changes in the carotenoids. Moreover, an increase in the number and size of first-order inflorescences (heads) as well as more intensive flower color were observed. Thus, it can be stated that the protein hydrolysate studied can be a beneficial component of both salinized and unsalinized soils in the cultivation of <em>A. houstonianum</em>.

Морфологические особенности, нектарная и семенная продуктивность тетраплоидных сортов гречихи

The task of research is the study of embryological characteristics and seed production of certain varieties of Fagopyrum esculentum Moench in a moderate continental climate of the Republic of Tatarstan. All kinds of violations of embryological processes were revealed at the studied varieties. The pollen fertility was averaged 80.0%. The high individual variability and intervarietal potential seed production and productivity factor were displayed, as well as their dependence on weather conditions. A low coefficient of efficiency was revealed. The authors proposed indirect methods for estimating the productivity index (according to the granulation size of inflorescences and to the economic factor), which let significantly to reduce the determination time of this parameter. The proposed methods can be used for the selection of high productive forms.

High temperatures result in smaller nurseries which lower reproduction of pollinators and parasites in a brood site pollination mutualism.

In a nursery pollination mutualism, we asked whether environmental factors affected reproduction of mutualistic pollinators, non-mutualistic parasites and seed production via seasonal changes in plant traits such as inflorescence size and within-tree reproductive phenology. We examined seasonal variation in reproduction in Ficus racemosa community members that utilise enclosed inflorescences called syconia as nurseries. Temperature, relative humidity and rainfall defined four seasons: winter; hot days, cold nights; summer and wet seasons. Syconium volumes were highest in winter and lowest in summer, and affected syconium contents positively across all seasons. Greater transpiration from the nurseries was possibly responsible for smaller syconia in summer. The 3–5°C increase in mean temperatures between the cooler seasons and summer reduced fig wasp reproduction and increased seed production nearly two-fold. Yet, seed and pollinator progeny production were never negatively related in any season confirming the mutualistic fig–pollinator association across seasons. Non-pollinator parasites affected seed production negatively in some seasons, but had a surprisingly positive relationship with pollinators in most seasons. While within-tree reproductive phenology did not vary across seasons, its effect on syconium inhabitants varied with season. In all seasons, within-tree reproductive asynchrony affected parasite reproduction negatively, whereas it had a positive effect on pollinator reproduction in winter and a negative effect in summer. Seasonally variable syconium volumes probably caused the differential effect of within-tree reproductive phenology on pollinator reproduction. Within-tree reproductive asynchrony itself was positively affected by intra-tree variation in syconium contents and volume, creating a unique feedback loop which varied across seasons. Therefore, nursery size affected fig wasp reproduction, seed production and within-tree reproductive phenology via the feedback cycle in this system. Climatic factors affecting plant reproductive traits cause biotic relationships between plants, mutualists and parasites to vary seasonally and must be accorded greater attention, especially in the context of climate change.

Distinct Signaling Mechanisms in Multiple Developmental Pathways by the SCRAMBLED Receptor of Arabidopsis

SCRAMBLED (SCM), a leucine-rich repeat receptor-like kinase in Arabidopsis (Arabidopsis thaliana), is required for positional signaling in the root epidermis and for tissue/organ development in the shoot. To further understand SCM action, we generated a series of kinase domain variants and analyzed their ability to complement scm mutant defects. We found that the SCM kinase domain, but not kinase activity, is required for its role in root epidermal patterning, supporting the view that SCM is an atypical receptor kinase. We also describe a previously uncharacterized role for SCM in fruit dehiscence, because mature siliques from scm mutants fail to open properly. Interestingly, the kinase domain of SCM appears to be dispensable for this developmental process. Furthermore, we found that most of the SCM kinase domain mutations dramatically inhibit inflorescence development. Because this process is not affected in scm null mutants, it is likely that SCM acts redundantly to regulate inflorescence size. The importance of distinct kinase residues for these three developmental processes provides an explanation for the maintenance of the conserved kinase domain in the SCM protein, and it may generally explain its conservation in other atypical kinases. Furthermore, these results indicate that individual leucine-rich repeat receptor-like kinases may participate in multiple pathways using distinct signaling mechanisms to mediate diverse cellular communication events.

Pollen transfer efficiency and its effect on inflorescence size in deceptive pollination strategies.

Pollination systems differ in pollen transfer efficiency, a variable that may influence the evolution of flower number. Here we apply a comparative approach to examine the link between pollen transfer efficiency and the evolution of inflorescence size in food and sexually deceptive orchids. We examined pollination performance in nine food-deceptive, and eight sexually deceptive orchids by recording pollen removal and deposition in the field. We calculated correlations between reproductive success and flower number (as a proxy for resources allocated during reproductive process), and directional selection differentials were estimated on flower number for four species. Results indicate that sexually deceptive species experience decreased pollen loss compared to food-deceptive species. Despite producing fewer flowers, sexually deceptive species attained levels of overall pollination success (through male and female function) similar to food-deceptive species. Furthermore, a positive correlation between flower number and pollination success was observed in food-deceptive species, but this correlation was not detected in sexually deceptive species. Directional selection differentials for flower number were significantly higher in food compared to sexually deceptive species. We suggest that pollination systems with more efficient pollen transfer and no correlation between pollination success and number of flowers produced, such as sexual deception, may allow the production of inflorescences with fewer flowers that permit the plant to allocate fewer resources to floral displays and, at the same time, limit transpiration. This strategy can be particularly important for ecological success in Mediterranean water-deprived habitats, and might explain the high frequency of sexually deceptive species in these specialised ecosystems.

Reproductive allocation in rhizomatous, seminiferous, and pseudoviviparous Leiothrix (Eriocaulaceae) species

Pseudoviviparous species are considered to rely almost entirely on vegetative propagation, because flowers are replaced by sprouts, and seedling recruitment is rare. We compared reproductive allocation (inflorescence and seed production) in three propagation modes presented by sympatric species of Leiothrix (Eriocaulaceae): rhizomatous and seminiferous (RS—L. crassifolia); rhizomatous, seminiferous, and pseudoviviparous (RSP—L. spiralis); and seminiferous and pseudoviviparous, in which seed production is considered rare due to reduced inflorescence size and small number of pistillate flowers (SP—L. arrecta and L. propinqua). We hypothesize that such propagation modes constitute a continuum of reproductive investment, that is: RS > RSP > SP. We harvested 154 Leiothrix spp. individuals at the Serra do Cipo, SE Brazil, from which we recorded the number of capitula and seeds, mean seed weight, and dry biomass allocated to plant structures. We then compared distinct propagation modes in relation to reproductive allocation, inflorescence-based and seed-based reproductive effort, and biomass partitioning. Contrary to expectations, the reproductive investment hierarchy found was SP ≥ RS > RSP. Our results do not fully concur with the current view that pseudoviviparous plants allocate few resources to reproduction. We suggest that the larger reproductive investment observed in SP helps to wait for better recruitment conditions in crowded and highly competitive mature populations (temporal escape), and to cope with destructive disturbances such as fire, since SP species lacks rhizomes.

Mean Daily Temperature Regulates Plant Quality Attributes of Annual Ornamental Plants

In protected environments, temperature is often regulated to produce ornamental crops for specific market dates. Temperature primarily controls plant developmental rate and thus production time, but it can also interact with light quantity to affect crop quality attributes such as flower number, branching, and biomass accumulation. We quantified how mean daily temperature (MDT) between 14 and 26 °C influenced quality characteristics of 15 common bedding plant crops. American marigold (Tagetes erecta), cup flower (Nierembergia caerulea), diascia (Diascia barberae), flowering tobacco (Nicotiana alata), geranium (Pelargonium ×hortorum), globe amaranth (Gomphrena globosa), heliotrope (Heliotropium arborescens), nemesia (Nemesia foetans), New Guinea impatiens (Impatiens hawkeri), osteospermum (Osteospermum ecklonis), pot marigold (Calendula officinalis), snapdragon (Antirrhinum majus), stock (Matthiola incana), and torenia (Torenia fournieri) were grown under two mean daily light integrals (9.0 and 18.0 mol·m−2·d−1) in five environmentally controlled greenhouse compartments with a 16-h photoperiod. As MDT increased from 14 to 26 °C, flower or inflorescence number decreased for nearly all crops. In six crops, flower or inflorescence size decreased as MDT increased, whereas in five crops, there was an initial increase in flower size with an increase in MDT and then a subsequent decrease at MDT greater than 20 °C. In 10 of the crops, shoot weight at flowering decreased linearly or quadratically with an increase in MDT. Branch number was inversely related with MDT in eight crops and was positively correlated with an increase in flower number. We conclude that in a majority of the crops studied, plant quality decreased as the MDT increased, which can at least partially be attributed to earlier flowering at the higher MDTs. Therefore, there is often a tradeoff between faster crop timing and higher plant quality, especially for plants with a low estimated base temperature (Tmin) for development.

Can floral display size compensate for Allee effects caused by low population abundance and density inSynthyris bullii(Plantaginaceae), a rare species?

Conservation seeks to address the issues of small population size, and the reproductive limitations confronting these populations. Sparse, small plant populations often suffer Allee effects such as pollinator limitation. However, some studies show that plants in sparse populations experience reduced resource competition. As a result, these plants may produce larger floral displays, which are also predicted to attract pollinators. The negative impacts from reduced floral quantity may thus be offset by improved floral quality. In a 2-yr field study, population abundance and density were quantified for 24 populations of Synthyris bullii (Plantaginaceae), a rare prairie endemic. In each population, data were collected on inflorescence size, fruit/seed set, and seed germination. Inflorescence size had a positive relationship with population inflorescence abundance and density. Fruit set and germination responded positively to floral quality (i.e., flower density). In comparison, seed set showed a positive relationship with only floral quantity (i.e., population abundance). Contrary to our predictions, inflorescence size and population size were not inversely related. While attractive floral displays in sparse populations potentially compensate in terms of fruit set, population abundance nevertheless plays an important role in seed set. Because floral quality and quantity differ in their ability to explain reproductive outcomes, studies should examine reproduction at several stages, otherwise the impacts of population size may be overlooked. Allee effects manifesting at a critical stage of reproduction, such as seed production, may act as a bottleneck impeding successful recruitment.