Resource Sinks Research Articles

How far need to go from peak to neutrality? Perspective from energy consumption emission offset analysis in Beijing-Tianjin-Hebei Agglomeration

Carbon emissions elimination in the rapid urbanization areas contributes to regional sustainable development and global climate change mitigation. With the target of carbon neutrality, the global top-class Beijing-Tianjin-Hebei Urban Agglomeration which confronts with the dual pressure of excess carbon emissions and shrink ecological space has increased its carbon reduction coordination cooperation, among which energy consumption carbon emission control and natural resource sink maintenance have been recognized as the key strategy. However, the study on carbon balance prediction is lack and the amount of energy consumption carbon emissions in the future can be offset by the ecological carbon sink is still unknown. To estimate the gap to carbon neutrality, this study proposes a framework for carbon offset analysis and prediction which takes various carbon emission scenarios and the potential of natural resource on carbon reduction into consideration. After the framework conduction in the agglomeration, it is revealed that the regional least carbon emissions of 29.51 Mt mainly derive from the population and economic growth brought by urbanization process, while the carbon sink predicted to be 2552.31 Kt is still far to cover the emissions. With the regional carbon offset rate decline from 0.68% to 0.63%, the ecological carbon sink in Beijing will offset 1.21% of its carbon emission, while the least ecological space keep city Tianjin is predicted to suffer the lowest offset rate of 0.09%. The research results contribute to recognize the key factors on carbon emission control and key areas for carbon maintenance in following years, as well as narrowing the gap to neutrality with both consideration of carbon emission reduction and sink maintenance.

Metabolomic responses to the mechanical wounding of Catharanthus roseus' upper leaves.

Plant secondary metabolites are used to treat various human diseases. However, it is difficult to produce a large number of specific metabolites, which largely limits their medicinal applications. Many methods, such as drought and nutrient application, have been used to induce the biosynthetic production of secondary metabolites. Among these secondary metabolite-inducing methods, mechanical wounding maintains the composition of secondary metabolites with little potential risk. However, the effects of mechanical stress have not been fully investigated, and thus this method remains widely unused. In this study, we used metabolomics to investigate the metabolites produced in the upper and lower leaves of Catharanthus roseus in response to mechanical wounding. In the upper leaves, 13 different secondary metabolites (three terpenoid indole alkaloids and 10 phenolic compounds) were screened using an orthogonal partial least squares discriminant analysis (OPLS-DA) score plot. The mechanical wounding of different plant parts affected the production of secondary metabolites. Specifically, when lower leaves were mechanically wounded, the upper leaves became a strong source of resources. Conversely, when upper leaves were injured, the upper leaves themselves became a resource sink. Changes in the source-sink relationship reflected a new balance between resource tradeoff and the upregulation or downregulation of certain metabolic pathways. Our findings suggest that mechanical wounding to specific plant parts is a novel approach to increase the biosynthetic production of specific secondary metabolites. These results indicate the need for a reevaluation of production practices for secondary metabolites from select commercial plants.

Bayesian Optimization for Chemical Reactions.

Reaction optimization is challenging and traditionally delegated to domain experts who iteratively propose increasingly optimal experiments. Problematically, the reaction landscape is complex and often requires hundreds of experiments to reach convergence, representing an enormous resource sink. Bayesian optimization (BO) is an optimization algorithm that recommends the next experiment based on previous observations and has recently gained considerable interest in the general chemistry community. The application of BO for chemical reactions has been demonstrated to increase efficiency in optimization campaigns and can recommend favorable reaction conditions amidst many possibilities. Moreover, its ability to jointly optimize desired objectives such as yield and stereoselectivity makes it an attractive alternative or at least complementary to domain expert-guided optimization. With the democratization of BO software, the barrier of entry to applying BO for chemical reactions has drastically lowered. The intersection between the paradigms will see advancements at an ever-rapid pace. In this review, we discuss how chemical reactions can be transformed into machine-readable formats which can be learned by machine learning (ML) models. We present a foundation for BO and how it has already been applied to optimize chemical reaction outcomes. The important message we convey is that realizing the full potential of ML-augmented reaction optimization will require close collaboration between experimentalists and computational scientists.

Adsorptive Removal of Atrazine From Contaminated Water Using Low-Cost Carbonaceous Materials: A Review

Extensive utilization of atrazine (estimated consumption of 70,000–90,000 tons per annum globally) to eliminate undesirable weeds has resulted in the accumulation of atrazine and its metabolites (diaminochlorotriazine, deisopropylatrazine, desethylatrazine, and atrazine mercapturate) in surface and groundwater above maximum permissible limits (drinking water: 3 μg L−1in the United States, 0.1 μg L−1in Europe, and 3.0 μg L−1by the WHO). Atrazine exhibited no to low degradation in aquatic environments; however, poor degradation in soil yields toxic metabolites, which serve as sinks for groundwater resources. Due to mobility, atrazine and its metabolites can persist in various environmental matrices for decades without degradation, posing a serious threat to ecosystem sustainability and, thus, being removed from water resources. Majority of conventional wastewater treatment technologies are either expensive or inefficient. The carbonaceous materials such as activated carbon, biochar, carbon nanotubes, and graphene have been employed as potent adsorbents for the efficient removal of atrazine along with its metabolites from wastewater. Thus, the efficacy of the aforementioned carbonaceous adsorbents for atrazine removal has been discussed in this article by reviewing 161 published articles. The literature survey demonstrated the highest atrazine adsorption capacity of activated carbons (13.95–712.10 mg g−1), followed by biochar (4.55–409.84 mg g−1) and carbon nanotubes (28.21–110.80 mg g−1). Atrazine adsorption onto the carbonaceous adsorbents is a complex process involving single or multiple mechanisms, such as hydrogen bonding, electrostatic interactions, van der Waals forces, hydrophobic interactions, π-π electron donor–acceptor interactions, pore filling, and partitioning. It is recommended that monitoring of atrazine and its metabolites in water resources and their impacts on human and animal lives be explored. Furthermore, modification of carbon-based adsorbents with chemical, mechanical, and thermal means, as well as development of hybrid systems, may completely remove the prevailing atrazine and its metabolites from world water resources.

Plant metabolism and defence strategies in the flowering stage: Time-dependent responses of leaves and flowers under attack.

Plants developing into the flowering stage undergo major physiological changes. Because flowers are reproductive tissues and resource sinks, strategies to defend them may differ from those for leaves. Thus, this study investigates the defences of flowering plants by assessing processes that sustain resistance (constitutive and induced) and tolerance to attack. We exposed the annual plant Brassica nigra to three distinct floral attackers (caterpillar, aphidand bacterial pathogen)and measured whole-plant responses at 4, 8and 12 days after the attack. We simultaneously analysed profiles of primary and secondary metabolites in leaves and inflorescencesand measured dry biomass of roots, leavesand inflorescences as proxies of resource allocation and regrowth. Regardless of treatments, inflorescences contained 1.2 to 4 times higher concentrations of primary metabolites than leaves, and up to 7 times higher concentrations of glucosinolates, which highlights the plant's high investment of resources into inflorescences. No induction of glucosinolates was detected in inflorescences, but the attack transiently affected the total concentration of soluble sugars in both leaves and inflorescences. We conclude that B.nigra evolved high constitutive rather than inducible resistance to protect their flowers; plants additionally compensated for damage by attackers viathe regrowth of reproductive parts. This strategy may be typical of annual plants.

Community‐level responses to increasing dryness vary with plant growth form across an extensive aridity gradient

AbstractAimPerennial plant communities are crucial for regulating ecological processes and maintaining ecosystem functions. Variation in community structure is driven by both biotic and abiotic factors, reflecting adaptation strategies of plant communities to various environments. Although much is known about the response of individual perennial plants to drier climates, empirical evidence of the community‐level responses to increasing dryness is limited.LocationEastern Australia; 1500 km gradient.TaxonPerennial plants.MethodsWe measured the abundance and size distribution (median, skewness and variance) of perennial plant communities from different growth forms (trees, shrubs and grasses), the spatial arrangement of trees in the overstorey and both biotic (competition) and abiotic (climate, soil properties) factors at 150 sites along an extensive aridity gradient from humid to arid areas. We used regression analyses and linear models to explore variation in community structure with increasing aridity and key driving factors for different perennial plant communities.ResultsVariation in community structure differed with growth form. As aridity increased, trees had wider canopies and were spatially aggregated, shrubs became miniaturised, but highly variable in size, and grasses comprised more larger individuals. Biotic and abiotic factors exerted different effects on different growth forms, with trees and shrubs consistently affected by competition and aridity, respectively, whereas grasses were weakly affected by aridity, summer rainfall and soil texture.Main conclusionsOur study highlights the idiosyncratic adaptation strategies used by trees, shrubs and grasses in response to drying climates at the community level through their effect on the size distribution or spatial aggregation. The structure of different perennial growth forms was influenced by different effects from either biotic (competition) or abiotic (climate, soil) factors. Under forecasted drier climates, canopy expansion and greater aggregation of trees might enhance resource sinks and shelter for diverse biota, potentially shielding plant communities against predicted aridification.

More is not necessarily better: The role of cover and spatial organization of resource sinks in the restoration of patchy drylands

A low-cost restoration action in patchy drylands worldwide is the installation of obstructions (hereafter, resource sinks) to break runoff pathways and retain resources. Field-works have studied how the effectiveness of this action depends on the materials installed. However, the influence and effectiveness of the cover and spatial organization of resource sinks have not been widely investigated. In this work, we use a well-known dryland model to study how different initial cover and spatial organization of installed resource sinks affect the recovered ecosystem. In agreement with field-work studies, our results confirm that the installation of resource sinks can restore degraded drylands that would not recover naturally. More importantly, a very small cover of resource sinks was sufficient to trigger vegetation recovery, while a high cover would lead to complete failure. Higher plant densities were reached when distribution and cover were similar to that of spatial self-organized vegetation in the reference healthy system (i.e., regular spatial distribution in our study system). Given the effectiveness of low cover installations, suggested by our work, combined with the low-cost materials needed, resource sinks have the potential to be a key contributor to the large restoration efforts needed to achieve land-degradation neutrality, particularly in developing countries.

ROOFTOP FARMING: AN ALTERNATIVE TO CONVENTIONAL FARMING FOR URBAN SUSTAINABILITY

In ecological terms, modern cities consume 75% of world resources with 2% of global land area and have become a parasite and a resource sink. Unmanaged planning and rapid development often result in the destruction of natural resources and loss of greenery. Pokhara is rapidly urbanizing into a megacity in Nepal and climate change caused by global warming is a great menace here. To support the rising requirement of quality food for the skyrocketing population, the main consumption centre should be mobilized for food production. Rooftop gardens are gaining relevance as they have the potential to meet the growing demand for food in cities and enhance the ecosystem along with the conservation of biodiversity. Thus, the addition of greenery element such as a green roof is becoming a trend to solve this problem in Pokhara. Establishment of green roofs in Pokhara city is arousing the interest of the government and public due to their demonstrated environmental benefits. The objective of this research is to inspect the existing practice and obstacles in rooftop farming that is faced by pr actitioners. Nagdhungha and Birauta are the areas of research here. Two practitioners are interviewed and sixty nonpractitioners are surveyed. The result shows that rooftop farming can benefit the environment by greatly reducing carbon in the atmosphere and can assist urban areas by reducing stormwater management cost. Furthermore, the paper demonstrates that the willingness to practice rooftop farming is high among urban dwellers and for future scope, some recommendations are provided in this research.

Photosynthetic activity of reproductive organs

During seed development, carbon is reallocated from maternal tissues to support germination and subsequent growth. As this pool of resources is depleted post-germination, the plant begins autotrophic growth through leaf photosynthesis. Photoassimilates derived from the leaf are used to sustain the plant and form new organs, including other vegetative leaves, stems, bracts, flowers, fruits, and seeds. In contrast to the view that reproductive tissues act only as resource sinks, many studies demonstrate that flowers, fruits, and seeds are photosynthetically active. The photosynthetic contribution to development is variable between these reproductive organs and between species. In addition, our understanding of the developmental control of photosynthetic activity in reproductive organs is vastly incomplete. A further complication is that reproductive organ photosynthesis (ROP) appears to be particularly important under suboptimal growth conditions. Therefore, the topic of ROP presents the community with a challenge to integrate the fields of photosynthesis, development, and stress responses. Here, we attempt to summarize our understanding of the contribution of ROP to development and the molecular mechanisms underlying its control.

Stem growth during seed production in soybean: Implications for pod yield

ABSTRACTIn soybean (Glycine max (L.) Merr.), stems remain a competitive carbon resource sink during reproduction. Radial stem expansion after termination of axial stem growth requires resources to produce secondary cell walls in secondary vascular tissues. The impact of both the timing and extent of secondary growth in stems on fruit production in soybean is unknown. We hypothesized that cultivars gaining higher amounts of secondary vascular tissues during seed filling would experience lower reproductive output. Four determinate cultivars were grown in a greenhouse and harvested at the beginning and ending of seed filling for biomass determination and tissue composition measurement (ImageJ-Fiji). Cultivar ‘Hanover’ entered seed filling with the lowest amount of secondary phloem. It produced the largest increase in radial stem expansion, largest seeds, and fewest undeveloped (aborted) fruits. The physiological role of active secondary phloem production in stems for seed production in soybean reproduction is unclear. We reject our initial hypothesis and propose that high fitness may require the concomitant growth of vegetative and reproductive organs.

Phytophagous insect oviposition shifts in response to probability of flower abortion owing to the presence of basal fruits.

Phytophagous insects use a wide range of indicators or associated cues to avoid laying eggs in sites where offspring survival is low. For insects that lay eggs in flowers, these unsuitable sites may be created by the host plant's resource allocation to flowers. In the sequentially flowering host plant, Yucca glauca, late‐opening distal flowers are more likely to be aborted in the presence of already‐initiated basal fruits because they are strong resource sinks. If flowers are aborted, all eggs of the phytophagous insect, Tegeticula yuccasella, within the flower die. We used the phytophagous insect T. yuccasella that lays eggs in and pollinates host plant Y. glauca flowers to test the hypothesis that phytophagous insect females are less likely to invest eggs in host plant flowers if basal fruits are present because they are more likely to be aborted. We also investigated potential predictors of arrival of T. yuccasella at inflorescences at the onset of flowering. These factors may influence a phytophagous insect's decisions to select oviposition sites. We carried out a behavioral experiment using wild‐caught T. yuccasella females on manipulated inflorescences with distal flowers with basal fruits and without fruits. As potential predictors of T. yuccasella arriving at inflorescences, we used floral display size and day of onset of flowering. In support of our hypothesis, our experimental results showed that T. yuccasella was significantly less likely to oviposit in distal flowers on inflorescences with basal fruits. We also found that T. yuccasella arrival was higher at inflorescences with larger floral display size and earlier in the flowering season. These findings uncover a novel indicator of unsuitable oviposition sites—the presence of basal fruits, that phytophagous insects use to make oviposition decisions. Further, our study contributes to the growing body of evidence that shows that females prefer sites that increase the probability of survival of their offspring.

Within-population variation in the chemistry of life: the stoichiometry of sexual dimorphism in multiple dimensions

In sexual species, phenotypic divergence between males and females, or sexual dimorphism, is often the source of the most staggering examples of phenotypic variation in nature. Theory suggests that exaggerated sexual traits should drive sex-specific nutritional demands. Advances in spectrometry enable rapid quantification of the elements that make up individuals and traits, which can be used to assess patterns of intraspecific variation and the contribution of nutritionally-demanding sexual traits to these patterns. We measured dimorphism in the whole body stoichiometry of Hyalella amphipods and examined whether nutritional demands of exaggerated sexual traits differ from those of similar traits not under sexual selection. We found striking sexual dimorphism in multivariate whole body elemental composition (i.e., the ionome), including elements important for organismal growth and performance. In males, the exaggerated, sexually-selected claw-like appendage (posterior gnathopod) differed significantly in mass-specific stoichiometry from a similarly sized and serially homologous non-sexual trait (fifth pereopod), indicating that there are fundamental differences in the construction of sexual traits in relation to similar traits that are not under sexual selection. While sexually selected traits do differ from non-sexual traits in their ionomes, we found that possessing an exaggerated trait does not change organismal stoichiometry, indicating that trait exaggeration may not be directly driving ionomic sexual dimorphism. Finally, we found that larger traits are not comparatively larger resource sinks for any element, suggesting that the possession of larger traits is not a function of greater allocation of resources. Together, we discovered substantial sexual dimorphism at the lowest level of organization, chemical elements. Such information illuminates predictions about dimorphisms in foraging behavior, nutritional physiology, and sex-specific selection on the underlying loci. High throughput, multidimensional data on sexual divergence in stoichiometric composition is a powerful tool in understanding the evolutionary ecology of sexual dimorphisms.

Towards a smart automated surface irrigation management in rice-growing areas in Italy

Italy is the leading rice producer in Europe, accounting for more than half of the total high-quality production of this crop. Rice is traditionally grown in fields that remain flooded starting with crop establishment until close to harvest, and this traditional irrigation technique (i.e., continuous submergence) is recognised as an important water resource sink (almost 40% of the irrigation water available worldwide is used for paddy areas). Meanwhile, the water management in rice areas requires a high level of labour because it is based on maintaining a predetermined water height in paddy fields and because the regulation of input and output flow is typically operated manually by the farmer. This study reveals the hardware and software characteristics of an automated and remote controlled technology tested for the first time in a rice farm near Pavia (Italy), during the 2016 growing season, aiming at a more efficient and less burdensome irrigation management system for rice fields. A water level sensor in the field provides the data required to govern the inflow regulation gate in real-time, according to the precise time to cut off the flow rate. Using a dedicated web page, the farmer can control flows, volumes and water levels in the fields by operating directly on the gate if necessary or setting the irrigation program according to his agronomic practices.

Fungal translocation - creating and responding to environmental heterogeneity

It has been known for a long time that fungi may transport substances in their hyphae. Experiments using radioactive tracer isotopes have greatly expanded our knowledge about translocation and have revealed that many fungi may circulate resources throughout their mycelia. This article outlines a conceptual framework for when and where net-translocation of resources takes place. Effects of substrate qualities, mycelial growth and activity as well as interactions with living plant hosts and other microorganisms are discussed and exemplified with experimental data. It is concluded that translocation from more or less remote parts of the mycelium enables fungi to colonise substrates with a low initial resource availability and to actively increase the resource availability in the substrates, turning the colonising mycelium from a resource sink into a source. Thus, translocation not only occurs in response to environmental heterogeneity, but also allows fungi to create heterogeneity in their growth environment.

Relationships among shoot sinks for resources exported from nodal roots regulate branch development of distal non-rooted portions of Trifolium repens L.

Two manipulative experiments tested hypotheses pertaining to the correlative control exerted by nodal roots on branch development of the distal non-rooted portion of Trifolium repens growing clonally under near-optimal conditions. The two experiments, differing in their pattern of excision to manipulate the number of branches formed at the first 9-10 phytomers distal to the youngest nodal root, each found that after 20 phytomers of growth the total number of lateral branches formed on the primary stolon remained between five and seven regardless of where the branches formed along the stolon. Additional treatments established that nodal roots influenced branch development via relationships among shoot sinks for the root-supplied resources rather than through variation in the supply of such resources induced by fluctuations in photosynthate supply to roots from branches. Regression analysis of data pooled from treatments of both experiments confirmed that shoot-sink relationships for root- supplied resources controlled the branching processes on the non-rooted portion of plants. A disbudding treatment, which removed all the apical and axillary buds present on basal branches, but left other branch tissues intact, increased branch development of the apical region in the same way as did complete excision of the basal lateral branches. The apical buds and the elongation processes occurring immediately proximal to the buds were thus identified as strong sinks for the root-supplied resources. Such results suggest that branch development on the non-rooted shoot portion distal to the youngest nodal root is regulated by competition among sinks for root-derived resources, of limited availability, necessary for the processes of elongation of axillary buds and the primary stolon apical bud.

Morphometric, allometric, and developmentally adaptive traits in red spruce and black spruce. I. Species and seed-source variation

The study objective was to compare intraspecific seed source and interspecifc variation of red spruce (Picea rubens Sarg.) and black spruce (Picea mariana (Mill.) BSP) in a number of morphometric, allometric, and adaptive traits. Analyses of variance for cotyledon number, root dry weight, shoot to root ratio, and seedling water balance revealed significant species effects. Germination time, total height, diameter, needle and stem wood dry weight, and survival had significant species effects and species × region interactions. Potential inbreeding depression effects were reflected in a positive relationship between height growth and percent germination and a negative relationship between height growth and germination time; these effects may have partly contributed to the species × region interactions. On average, 66% of the height growth difference between the species may be attributable to earlier germination and the other 34% to faster growth. Covariate allometric analysis showed that black spruce had a 39% higher shoot to root ratio than red spruce. Red spruce allocated 25% more dry weight (per unit needle weight) towards roots than did black spruce. When the resource sinks (stem wood and roots) are summed, black spruce is 8.6% more efficient at converting resources into sink biomass than is red spruce.

Interactions between growth, herbivory and long-term foliar dynamics of Scots pine

It is generally thought that carbon-limited conifers with low priority stem growth investment will suffer significantly reduced wood formation following defoliation by insects, as long as resource sinks (apical buds and young needles) are unaffected compared to sources (mature needles). We examined the long-term consequences of periodic defoliation by a moth (Bupalus piniaria L.) on the growth of Scots pine (Pinus sylvestris L.), by retrospectively determining annual rates of needle retention using the needle trace method, and comparing these rates with patterns of radial growth obtained by tree-ring analysis. Cumulative moth densities in the current and previous year had the strongest negative influence on subsequent tree growth. Radial and volume increments were reduced substantially (by up to 50%) for 2–3 years after peaks in the moth population. In turn, tree growth was positively correlated with needle retention, with better growth promoting better retention in the following two seasons. This dominant relationship masked the more subtle impact of B. piniaria on needle retention. However, when each needle cohort was examined separately, it was possible to detect the immediate effects of B. piniaria on the loss of the youngest (0 to 1-year-old) needle cohort. Needle budgeting differed for trees in two study compartments, where the rate of tree growth was evidently different. In the compartment where trees grew more slowly they retained a greater number of needle sets over time by shedding fewer of the older needles, but they responded more quickly to the negative effects of the defoliator by losing needles more rapidly in years when the defoliator was abundant.

The Influence of Fruit on the Regulation of Internal Ethylene Concentrations and Sex Expression inCucurbita texana

Plants with labile sex expression often regulate the production of pistillate and staminate flowers on the basis of developmental and environmental conditions. In many monoecious plant species, developing fruits inhibit pistillate flower production and promote staminate flower production. Because the phytohormone ethylene promotes pistillate flower production in a variety of wild and cultivated plant species, we examined the influence of fruit development on internal ethylene production and their combined effects on sex expression in field‐grown Cucurbita texana (Cucurbitaceae). We compared the sex expression of plants with fruit and without fruit, and we measured internal ethylene concentrations within the hollow internodes of their branches. Plants without fruit had more than twice as many pistillate flowers than plants with fruit. Ethylene was greatest within internodes just below the tips of branches compared with more basal internodes (2–21 internodes from the tip) in both fruiting and fruitless treatments. Ethylene concentrations within branches with fruit were highest 18 d after pollination, just as fruits reached their maximum volume. Branches with two or more developing fruits had the lowest ethylene concentrations, whereas ethylene levels were significantly higher on fruitless branches and one‐fruited branches. Our results indicate that young developing fruits may send a signal that inhibits ethylene production, leading to the promotion of staminate flowers, and that, when fruits are no longer strong resource sinks, ethylene concentrations increase and promote pistillate flower production.

Ecosystem Management of Desertified Shrublands in Israel

The objectives of this study were to understand the ecological processes and possible management strategies in desertified shrublands. We hypothesized that biological production and diversity in desertified shrublands in the Negev in Israel are low due to water, soil, and nutrient leakage from the ecosystem. We designed a series of field experiments in order to examine (a) whether source–sink relationships exist between the crusted soil and the shrub patches, (b) whether resources (water, soil, and nutrients) leak from the system, and (c) whether management, which changes the landscape mosaic by introducing new sink patches that reduce leakage of resources, may increase productivity and diversity. The results indicate that the low number of shrub patches, which serve as sinks for resources, leads to water, soil, and nutrient leakage from the ecosystem. This leakage reduces ecosystem production and diversity. We found that artificially created pits, which act as sinks for resources, decrease leakage and increase biomass production and annual plant species diversity. Based on the experimental results, we developed conceptual models for shrubland desertification and ecosystem management. The models are based on a source–sink relationship between two patch types characteristic of shrublands. The models relate landscape productivity to the number of sink patches and suggest that, in cases where there are too few sinks, artificially created sink patches should be added. Management methods were developed to reduce resource leakage in the desertified shrubland of the Negev. Methods included construction of man-made pits in the landscape that add resource-enriched patches to the landscape. These patches are used to create parks consisting of clusters of trees integrated into a matrix of shrubs and herbaceous vegetation. The managed parks are used for recreational purposes and for rangeland.

The effect of plant size on the expression of cleistogamy in Mimulus nasutus

1. Most dimorphic angiosperm species produce chasmogamous flowers adapted for allogamy and cleistogamous flowers adapted for autogamy. Plant size is an important internal environmental factor and several studies have suggested an adaptive strategy whereby cleistogamous flowering ensures a basic seed output while larger plants can spare resources to make additional investment in the more expensive but presumably more fit outcrossed seed produced by chasmogamous flowering. This study tests the effect of plant size on the percentage of chasmogamy in a species, Mimulus nasutus, where both the cleistogamous and chasmogamous flowers are autogamous and so seed from chasmogamous flowers has no genetic advantage. 2. We measured change in expression of cleistogamy/chasmogamy in glasshouse‐grown plants of different sizes and architecture. Size was manipulated by varying the length of time for which the plants were grown under short days. Architecture was manipulated by removing stems. 3. We found that increased size led to an increase in the percentage of chasmogamy in M. nasutus. This is unexpected given the lack of genetic advantage of outcrossing and suggests that this effect can occur as a direct result of increased resource availability without the necessity of selection for progeny fitness. 4. An increase in plant size was also found to lead to an increase in resource sinks (developing flowers and seed capsules on other parts of the plant). As increased plant size can therefore produce both increased total resources and increased number of resource sinks, the net resources available to a developing flower will be a balance of these two effects. Resource re‐allocation is shown to occur between flowers on a stem, between stems and between flowers and seed set. In each case, this results in a net decrease in resources to new flowers and so results in there being only sufficient resources for cleistogamous flowering. 5. We discuss the difficulties of using species with varying growth forms to test the hypothesis that expression of allogamous chasmogamy increases with plant size because of the genetic advantage of outcrossing.