Pollen Supplementation Experiments Research Articles

Does pollination interact with the abiotic environment to affect plant reproduction?

Abiotic and biotic components of the environment both limit plant reproduction, but how they interact with one another in combination is less understood. Understanding these interactions is especially relevant because abiotic and biotic environmental components respond differently to various global change drivers. Here we aim to understand whether the effects of pollination (biotic component) on plant reproduction depend on soil moisture (abiotic component), two factors known to affect plant reproduction and that are changing with global change. We conducted pollen supplementation experiments for two plant species, Delphinium nuttallianum and Hydrophyllum fendleri, in subalpine meadows in the Western USA across four years that varied in soil moisture. In a separate one-year field experiment, we factorially crossed water addition with pollen supplementation. We measured proportion fruit set, seeds per fruit, and seeds per plant, in addition to stomatal conductance, to determine whether plant physiology responded to watering. In the four-year study, only H. fendleri reproduction was pollen limited, and this occurred independently of soil moisture. Experimental water addition significantly increased soil moisture and stomatal conductance for both species. The effect of pollen addition on reproduction depended on the watering treatment only for H. fendleri fruit production. Reproduction in D. nuttallianum was not significantly affected by pollen addition or water addition, but it did respond to interannual variation in soil moisture. Although we find some evidence for the effect of a biotic interaction depending on abiotic conditions, it was only for one aspect of reproduction in one species, and it was in an unexpected direction. Our work highlights interactions between the abiotic and biotic components of the environment as an area of further research for improving our understanding of how plant reproduction responds to global change.

PolLimCrop, a global dataset of pollen limitation in crops

Pollination is a crucial ecosystem service for maintaining plant communities and food production. 75% of the main crops depend on or benefit from pollination services provided by animal pollinators. However, when these services are insufficient and/or inefficient, crops experience pollen limitation with, often, lower associated yield, which may translate into economic losses. We constructed a global dataset that gathers studies with pollination experiments, aiming to provide pollen limitation values of animal-pollinated crops worldwide. Pollination experiments included hand pollen supplementation treatments, where plants were subjected to pollen supplementation of outcross pollen, and natural pollination treatments. The PolLimCrop dataset comprises 294 studies and 1169 unique pollen supplementation experiments with values of pollen limitation for 108 crops, spanning 50 years and 62 countries.

Sexual dimorphism and female advantage hypothesis in the gynomonoecious-gynodioecious Dianthus plumarius (Caryophyllaceae)

Abstract To explain the co-existence and maintenance of females along with hermaphrodite plants, the female advantage hypothesis has been proposed where females should show greater fecundity compared to their conspecific hermaphrodites. On the other hand, greater attraction would be selected in the hermaphrodites to increase their male function, potentially leading to larger showier flowers, with more rewards. Here, I tested the sexual dimorphism trade-off hypothesis with the gynomonoecious-gynodioecious Dianthus plumarius (Caryophyllaceae), in the gardens of Bariloche (Patagonia, Argentina). I measured in female and hermaphrodite plants: flower size, nectar volume and concentration, flower lifespan, ovule production, seed number, seed set and seed weight. Additionally, bagging and pollen supplementation experiments were carried out to evaluate pollen limitation, probability of apomixis, if spontaneous autogamy is possible, and to examine the importance of pollen origin. I found that hermaphrodite flowers are more attractive, with larger-sized flowers and higher nectar volume, whereas female flowers compensate with longer lifespan of stigmatic receptivity and more concentrated nectar. Despite ovule number was lower in female flowers, these showed higher seed set and produced more and heavier seeds than hermaphrodites under open pollination. No evidence of apomixis was found in females, but spontaneous autogamy may occur in hermaphrodites. Hand-pollination experiments showed first that both flower types suffered pollen limitation, but it was higher on hermaphrodite flowers. Finally, despite self-compatibility, pollen origin is important because hand self-pollination decreases seed weight. These findings provide strong evidence in support of the mechanisms and underlying conditions that would allow the co-existence and maintenance of female and hermaphrodite individuals within populations.

Pollen limitation failing reproductive success in selected animal pollinated trees of tropical moist deciduous forest of north-eastern hill region, India

Abstract The aim of this study was to estimate reproductive effort and success in tropical trees and to examine the effect of pollen limitation on reproductive success. Pollen limitation was assessed through pollen supplementation experiment to contrast the open pollination treatment. The taxa selected were Bombax ceiba, Erythrina stricta (ornithophilous trees), Lagerstroemia speciosa, Mesua ferrea and Schima wallichii (entomophilous trees). Index of pollen limitation was highest in Bombax ceiba and Erythrina stricta (both self-incompatible species). The remaining three species were partially self-incompatible with favouring selfing in Lagerstroemia speciosa and Mesua ferrea and supporting outcrossing in Schima wallichii. Therefore, the high index of pollen limitation in Bombax ceiba and Erythrina stricta might be due to the effect of either lacking quality pollen or lacking bird pollinators. All five species produce a large amount of pollen at individual tree level in the order of 108 (Erythrina stricta) to 1010 (Mesua ferrea). Fruit and seed set following pollen supplementation were higher than the open pollination (as control) in all studied species. Pollen limitation in this study is likely associated with the effectiveness of pollinator and their frequency, as all the studied species had produced ample pollen at tree crown level which ultimately leads to pollinator resource limitation in tropical trees.

Spatio-Temporal Variations in Pollen Limitation and Floral Traits of an Alpine Lousewort (Pedicularis rhinanthoides) in Relation to Pollinator Availability.

Populations of the same plant species living in different locations but flowering at different times may vary in pollinator availability and floral traits. However, the spatial and temporal links between floral traits and pollination are rarely included in single studies. In this study, three populations of an alpine lousewort, Pedicularis rhinanthoides Schrenk subsp. tibetica (Bonati) Tsoong, were surveyed to detect the variations in floral traits and pollinator activity. We hypothesized that floral divergence was spatio-temporally correlated with pollen limitation (PL) in relation to pollinators. Sampled plants from each population were divided into three groups, according to flowering stage: early, peak, and late. Pollen-supplementation experiments and investigations into pollinators, reproductive success, and floral traits were conducted on the plants from the different flowering stages and across the populations. Our results showed that the extent of PL varies across populations and among flowering stages. Populations in which more pollinators were recorded displayed a lower extent of PL. Furthermore, the temporal differences in PL showed a similar pattern for the three populations; the plants from the peak flowering stage suffered slighter PL than those from the other two stages. Nevertheless, some of the floral traits displayed similar spatial and temporal patterns to the PL, while the others only varied among the populations spatially. The results indicated that the performance of floral traits in a particular spatial-temporal situation shows they are well adapted to the corresponding pollination environment, which might help plants to optimize their reproductive fitness under different abiotic factors.

Does pollen limitation limit plant ranges? Evidence and implications.

Sexual reproduction often declines towards range edges, reducing fitness, dispersal and adaptive potential. For plants, sexual reproduction is frequently limited by inadequate pollination. While case studies show that pollen limitation can limit plant distributions, the extent to which pollination commonly declines towards plant range edges is unknown. Here, we use global databases of pollen-supplementation experiments and plant occurrence data to test whether pollen limitation increases towards plant range edges, using a phylogenetically controlled meta-analysis. While there was significant pollen limitation across studies, we found little evidence that pollen limitation increases towards plant range edges. Pollen limitation was not stronger towards the tropics, nor at species' equatorward versus poleward range limits. Meta-analysis results are consistent with results from targeted experiments, in which pollen limitation increased significantly towards only 14% of 14 plant range edges, suggesting that pollination contributes to range limits less often than do other interactions. Together, these results suggest pollination is one of the rich variety of potential ecological factors that can contribute to range limits, rather than a generally important constraint on plant distributions. This article is part of the theme issue 'Species' ranges in the face of changing environments (part I)'.

Effects of climate change and pollen supplementation on the reproductive success of two grassland plant species.

Climate change has the potential to alter plant reproductive success directly and indirectly through disruptions in animal pollination. Climate models project altered seasonal precipitation patterns, and thus, the effects of climate change on available resources and pollination services will depend on the season. Plants have evolved reproductive strategies to so they are not limited by either pollen or water availability in their reproductive success, and therefore, we expect that the disruption of climate change might cause plants to be more pollen limited in seasons that become wetter than they were historically. In this study, we conducted a pollen supplementation experiment within the Global Change Experiment Facility (GCEF) in Central Germany. The GCEF experimentally manipulates future climate based on a realistic scenario of climate change for the region (drier summers and wetter springs and falls) in a native grassland ecosystem. We quantified seed production of two perennial species Dianthus carthusianorum and Scabiosa ochroleuca in response to pollination treatments (control, supplement), climate treatments (ambient and future) and season (summer and fall). Dianthus carthusianorum produced more seeds in future climate conditions independent of the season, but only when given supplemental pollen. Both species showed an increased reproduction in summer compared with the fall. We did not find evidence for our specific expectation of higher pollen limitation in the future climate and fall season (i.e., no three‐way interaction pollination × season × climate), which might be explained by the high‐drought tolerance and generalized pollination of our focal plant species. We conclude that plant reproductive success has the potential to change with changing climates and that this change will depend on how pollinator services change in the future. We offer many suggestions for future studies that are necessary to understand the context dependence and underlying mechanisms of plant reproductive responses to climate.

Pollinator dependence but no pollen limitation for eight plants occurring north of the Arctic Circle.

Effective interactions between plants and pollinators are essential for the reproduction of plant species. Pollinator exclusion experiments and pollen supplementation experiments quantify the degree to which plants depend on animal pollinators and the degree to which plant reproduction is pollen limited. Pollen supplementation experiments have been conducted across the globe, but are rare in high latitude regions. To fill this knowledge gap, we experimentally investigated the dependence on animal pollinators and magnitude of pollen limitation in eight plant species north of the Arctic Circle in Lapland, Finland. Our findings show that all plant species were pollinator dependent, but not pollen limited. We discuss several mechanisms that might buffer our focal plants from pollen limitation, including plant and pollinator generalization, and attractive plant traits. Our results demonstrate that many plant species north of the Arctic Circle are currently receiving adequate pollinator service and provide a baseline for future comparisons of pollinator dependence and pollen limitation in the Arctic across space and time.

A review of the challenges and opportunities for restoring animal-mediated pollination of native plants.

Ecological restoration is increasingly implemented to reverse habitat loss and concomitant declines in biological diversity. Typically, restoration success is evaluated by measuring the abundance and/or diversity of a single taxon. However, for a restoration to be successful and persistent, critical ecosystem functions such as animal-mediated pollination must be maintained. In this review, we focus on three aspects of pollination within ecological restorations. First, we address the need to measure pollination directly in restored habitats. Proxies such as pollinator abundance and richness do not always accurately assess pollination function. Pollen supplementation experiments, pollen deposition studies, and pollen transport networks are more robust methods for assessing pollination function within restorations. Second, we highlight how local-scale management and landscape-level factors may influence pollination within restorations. Local-scale management actions such as prescribed fire and removal of non-native species can have large impacts on pollinator communities and ultimately on pollination services. In addition, landscape context including proximity and connectivity to natural habitats may be an important factor for land managers and conservation practitioners to consider to maximize restoration success. Third, as climate change is predicted to be a primary driver of future loss in biodiversity, we discuss the potential effects climate change may have on animal-mediated pollination within restorations. An increased mechanistic understanding of how climate change affects pollination and incorporation of climate change predictions will help practitioners design stable, functioning restorations into the future.

Progressive deterioration of pollination service detected in a 17-year study vanishes in a 26-year study.

Widespread reports of declining populations of pollinators have raised concerns that plant populations may be incurring increasing shortfalls in pollination, but few studies have measured pollination deficits over enough seasons to detect such changes. I have conducted pollen-supplementation experiments in a wild population of the glacier lily (Erythronium grandiflorum, Liliaceae) from 1993 to 2018. Pollination deficits were estimated by comparing the fruit set of hand-pollinated, single-flowered plants to that of open-pollinated controls. For a subset of years, seed set data were also available. A previous publication reported a significant deterioration of pollination in this population from 1993 to 2009, and suggested phenological dislocation as a possible cause. That deterioration is no longer evident in the longer-term data set. Very long time series may be necessary to detect temporal trends in pollination service. This population consistently experiences stronger pollination deficits before its flowering peak than after. This heterogeneity suggests caution in characterizing a population as pollination-limited or not, even within a single season.

Pollen limitation and seed set associated with year-to-year variation in flowering of Gmelina arborea in a natural tropical forest

The year-to-year variations in flowering, pollen and fruit production in ten Gmelina arborea individuals in a natural forest were observed over a period of five years, 2009−2013, and pollinator visits were observed closely over two years, 2011 and 2012. A pollen supplementation experiment was also undertaken in two years (2011 and 2012) of contrasting flowering levels. Considerable year-to-year variations were observed in flower, pollen and fruit production. The observed variation represented a normal sequence of good-year and poor-year cycling which is most parsimoniously attributed to resource allocation. The average level of pollen production per individual tree in good flowering years oscillated between 6.6 and 9.62 × 108, which in the poor flowering years was between 1.92 and 3.07 × 108. The magnitude of pollen limitation across years was highly significant (p < 0.0001). Fruit set through supplemental pollination was 73% and 96% greater than that of the open-pollinated branches in the year 2011 and 2012, respectively. Pollen limitation, irrespective of the arrival of outcross pollen, can reduce annual seed set in predominantly bee-pollinated trees. However, various other factors may cause flower abortion in addition to pollen limitation. The results of this study would be very valuable to the seed orchard managers and the silviculturists to manage the seed production areas (SPAs) of G. arborea. The study ultimately recommends supplemental pollination in seed orchards of G. arborea for better genetic gain and good seed yield.

GloPL, a global data base on pollen limitation of plant reproduction

Plant reproduction relies on transfer of pollen from anthers to stigmas, and the majority of flowering plants depend on biotic or abiotic agents for this transfer. A key metric for characterizing if pollen receipt is insufficient for reproduction is pollen limitation, which is assessed by pollen supplementation experiments. In a pollen supplementation experiment, fruit or seed production by flowers exposed to natural pollination is compared to that following hand pollination either by pollen supplementation (i.e. manual outcross pollen addition without bagging) or manual outcrossing of bagged flowers, which excludes natural pollination. The GloPL database brings together data from 2969 unique pollen supplementation experiments reported in 927 publications published from 1981 to 2015, allowing assessment of the strength and variability of pollen limitation in 1265 wild plant species across all biomes and geographic regions globally. The GloPL database will be updated and curated with the aim of enabling the continued study of pollen limitation in natural ecosystems and highlighting significant gaps in our understanding of pollen limitation.

A review of European studies on pollination networks and pollen limitation, and a case study designed to fill in a gap.

Anthropogenic environmental change disrupts interactions between plants and their animal pollinators. To assess the importance of different drivers, baseline information is needed on interaction networks and plant reproductive success around the world. We conducted a systematic literature review to determine the state of our knowledge on plant–pollinator interactions and the ecosystem services they provide for European ecosystems. We focussed on studies that published information on plant–pollinator networks, as a community-level assessment of plant–pollinator interactions and pollen limitation, which assesses the degree to which plant reproduction is limited by pollinator services. We found that the majority of our knowledge comes from Western Europe, and thus there is a need for baseline assessments in the traditional landscapes of Eastern Europe. To address this data gap, we quantified plant–pollinator interactions and conducted breeding system and pollen supplementation experiments in a traditionally managed mountain meadow in the Western Romanian Carpathians. We found the Romanian meadow to be highly diverse, with a healthy plant–pollinator network. Despite the presence of many pollinator-dependent plant species, there was no evidence of pollen limitation. Our study is the first to provide baseline information for a healthy meadow at the community level on both plant–pollinator interactions and their relationship with ecosystem function (e.g. plant reproduction) in an Eastern European country. Alongside the baseline data, we also provide recommendations for future research, and the methodological information needed for the continued monitoring and management of Eastern European meadows.

Pollen limitation and resource limitation affect the reproductive success of Medicago sativa L.

BackgroundA large proportion of the flowers and ovules of plants do not develop into fruits and seeds. Plant reproduction may be limited because of pollen limitation and resource limitation. Medicago sativa L. is an ecologically important species in northwest China. We conducted a pollen supplementation experiment to determine the degree of pollen limitation in this species and detect the possible effects of resource allocation on pollen supplementation. We crossed two factors, pollen level (natural condition and hand pollinated) and resource level (control, water added, and fertilizer added), to estimate the effects of pollen addition and resource limitation on the opening of flowers and seed set. We also analyzed the floral characters, visitation frequency of pollinators and pollinator activity to estimate the effect of pollinators on the reproduction of M. sativa.ResultsOur results indicated that addition of pollen to some flowers did not divert resources from other flowers and that the addition of pollen boosted the seed set per flower, with no effect on flower number. The primary effect of resource limitation was on the number of flowers produced; however, there was no significant effect on seed set per flower. These findings showed that pollen limitation was an important limiting factor for seed set. In addition, Andrena lebedevi Popov was identified as the most effective pollinator, and pollinator visiting and activity affected reproduction success in M. sativa.ConclusionsWe found outcrossing was dominant in the breeding system and insect pollination played an important role in outcrossing. These findings have identified the dominant factor influencing seed set of M. sativa. This study aspires to contribute to a better understanding of pollen limitation, resource limitation and reproductive success.

Resurgence of specialized shade coffee cultivation: Effects on pollination services and quality of coffee production

Since the early 2000s, there has been a resurgence in shade coffee production on the island of Puerto Rico. The newly restored specialized shade canopy consists of four native tree species, three of which are nitrogen fixers, and is intended to provide 30% shade cover once the trees are matured. Though much is known about the benefits of rustic and traditional shade plantations to coffee production, there is little information available for specialized shade plantations. Here, we investigate the ways in which fruit set, seed predation, bean weight, proportion of peaberries (i.e., malformed fruits), and beverage quality differ between sun and specialized shade plantations of Coffea arabica and Coffea canephora. Additionally, to assess whether coffee plants were pollen limited, we conducted a pollen supplementation experiment in which we compared pollen deposition and berry production on hand-pollinated branches to those of naturally, open-pollinated ones. We found that there was no evidence of pollen limitation on fruit set between sun and specialized shade plantations of C. arabica or C. canephora. We found that specialized shade benefits the proportion of C. arabica fruit set, without compromising bean weight or the proportion of peaberries produced. In comparison, C. canephora showed no improvement in the proportion of fruits set with specialized shade; however, beans from open-pollinated flowers weighed more in specialized shade than sun. Beverage quality was marginally better under shade, and for hand-pollinated flowers. Our results add to the limited body of work investigating the benefits of specialized shade coffee plantations on ecosystem services.

Small and surrounded: population size and land use intensity interact to determine reliance on autonomous selfing in a monocarpic plant.

Habitat fragmentation has transformed landscapes globally, leaving remnants embedded within a complex matrix that is rapidly becoming more developed. For many plant populations, the associated factors of decreased size and intensification of land use surrounding them are expected to increase pollen limitation ('PL'), unless autonomous self-pollination provides reproductive assurance ('RA'). Decreased pollinator visitation is often assumed to drive these patterns, but other, less studied mechanisms might include increased heterospecific pollen transfer or decreased conspecific pollen availability via florivory. I investigate how PL and RA and their potential underlying mechanisms vary with population size and land use intensity surrounding populations in the biennial Sabatia angularis (Gentianaceae). I estimated the capacity for seed production via autonomous self-pollination (i.e. autofertility). Over 2 years in 22 S. angularis populations across a fragmented landscape, I performed emasculation and pollen supplementation experiments measuring RA and PL, and quantified visitation rates of potential pollinators and a pollen consumer, conspecific pollen loads and rates of heterospecific pollen deposition. Autofertility based on fruit mass was 93 % under PL but only 51.6 % relative to maximal conditions. PL and RA were significant on average across populations in the first year of study. Variation in RA was significantly influenced by the interaction between population size and land use intensity, which in turn rendered PL independent of these factors. Visitation and heterospecific pollen deposition rates were greatest in small populations and declined with population size, while conspecific pollen loads were greatest in intermediate sized populations. Increased reliance on RA is predicted in small S. angularis populations surrounded by intense development, which can explain elevated selfing rates in fragmented populations of plant species more generally. Results from this study point toward forces such as heterospecific pollen transfer, self-pollen limitation or resource availability influencing the need and ability to rely on RA.

Pollen limitation and reproduction of three plant species across a temperature gradient in western Greenland

ABSTRACT Rapid climate change in the Arctic may increase sexual reproduction in plants because of changes in both abiotic factors, such as temperature, and biotic factors, such as pollination. Pollination may currently limit plant reproduction in the Arctic, where cold temperatures hinder pollinator activity. To understand how warming may affect pollination and plant reproduction, we studied three plant species in western Greenland. Two species were hermaphroditic and insect-pollinated (Vaccinium uliginosum and Chamerion latifolium), and one was dioecious and insect- and wind-pollinated (Salix glauca). We measured how pollinator visitation and plant reproduction varied across three temperature zones. We also conducted pollinator exclusion and pollen supplementation experiments to measure pollinator dependence and pollen limitation. Proportion of fruit set in Vaccinium and Salix was pollen limited in every temperature zone, and Vaccinium and Chamerion depended on pollinator-mediated outcrossing for maximum reproductive success. Furthermore, higher pollinator visitation to Vaccinium in the warmer temperature zones mirrored lower pollen limitation and higher fruit set, suggesting that temperature zone indirectly influenced reproduction via changes in pollination. Taken together, our results demonstrate that both abiotic factors and pollination are important in limiting reproduction in the Arctic and that plant–pollinator interactions can mediate the response of plant reproduction to warming.

Pollination Ecology ofPolylepis tomentella(Rosaceae), an Andean Anemophilous Tree Presenting a Potential Floral Fungal Infection

Premise of research. Anemophily is considered to be a mechanism that evolved to promote pollination success. However, reproductive output can decrease if pollen loads are scarce due to low abundance of compatible mates or floral infections. Here we analyze the effects of breeding system, pollen limitation, and a potential floral fungal infection on the reproductive output of the Andean tree Polylepis tomentella (Rosaceae).Methodology. We performed pollen supplementation experiments in the field to assess the extent of the effect of pollen limitation on fruit and seed set and to identify any pre- or postzygotic self-incompatibility responses within receptive pistils. Supplementary scanning electron microscopy and epifluorescence microscopy were used to observe the possible effects of a potential floral fungal infection on sexual reproduction.Pivotal results. Pollen supplementation did not increase fruit and seed set, suggesting weak evidence of pollen limitation. Most stigmas from self- and cross-pollinate...

Density‐dependent reproduction and pollen limitation in an invasive milkweed, Calotropis procera (Ait.) R. Br. (Apocynaceae)

AbstractCalotropis procera (Ait.) R.Br. (Apocynaceae), an invasive woody milkweed, has expanded its range in northern Australia affecting rangeland and pastoral productivity. While self‐compatibility should enhance the species range expansion, spread of C. procera is limited by the availability of larger wasp and bee species that are able to vector its solid pollinia. Pollination efficiency is thus likely dependent on both pollinator abundance and plant density. Calotropis procera flowers year round in Australia but fruiting is limited to the warm months of the year when pollinators are most abundant, indicating that seasonal regulation of reproduction may be due to pollinator limitation. We examine the propositions that C. procera reproduction is regulated by the interaction between plant population density and pollinator pressure and that low pollinator pressure causes low per capita plant fecundity. All pollinators belonged to Order Hymenoptera and pollinator composition was similar at six of the seven sites. Fruit production per plant (fecundity) was lower above and below intermediate densities (350–550 plants ha−1) of flowering plants with evidence of a weak Allee effect at lower plant density. Pollinator visitation rates per plant were low at high and low plant densities, and greatest at intermediate densities, while pollen supplementation experiments showed that C. procera is pollen limited (Pollen Limitation Indexfruit = 0.9) even at intermediate densities. Pollen limitation caused by low pollinator pressure at low plant densities and pollinator satiation at high plant densities may account for these fruit production trends. Management should be conducted in the colder months when pollinator pressure is low and plants are not reproducing. In addition, where stand eradication cannot be achieved in one attempt, management should reduce flowering plants to below intermediate densities where the fecundity per plant is low.

Important Biological Knowledge for Management of Cooley's Meadowrue (Thalictrum cooleyi), a Federally Endangered Endemic of Pine Savannas

ABSTRACT Thalictrum cooleyi (Cooley's meadowrue, Ranunculaceae) is a federally endangered dioecious herb of wet pine savannas of the southeastern United States. We studied aspects of T. cooleyi biology crucial to conservation including its association with woody species, reproduction, and genetic structure in 11 populations in North Carolina and Georgia. Thalictrum cooleyi presence was negatively associated with canopy closure, but positively associated with shrub cover, including wax myrtle Morella cerifera. Deviations from strict dioecy are uncommon in T. cooleyi. Sex ratios differed significantly from 1:1, but despite male-bias in populations, pollen supplementation experiments found evidence for pollen limitation to seed set. Seeds are dormant at maturity. Cold stratification or gibberellic acid can break dormancy. Warm temperatures followed by cold stratification may increase germinability. Germination rates were low, likely due to low seed viability. Thalictrum cooleyi can be propagated vegetatively...