Plant-environment Interactions Research Articles

Plant Abiotic Stress Challenges from the Changing Environment.

Plant Abiotic Stress Challenges from the Changing Environment.

Responses of hydraulics at the whole-plant level to simulated nitrogen deposition of different levels in Fraxinus mandshurica.

Nitrogen (N) deposition is expected to have great impact on forest ecosystems by affecting many aspects of plant-environmental interactions, one of which involves its influences on plant water relations through modifications of plant hydraulic architecture. However, there is a surprising lack of integrative study on tree hydraulic architecture responses to N deposition, especially at the whole-plant level. In the present study, we used a 5-year N addition experiment to simulate the effects of six different levels of N deposition (20-120 kg ha(-1) year(-1)) on growth and whole-plant hydraulic conductance of a dominant tree species (Fraxinus mandshurica Rupr.) from the typical temperate forest of NE China. The results showed that alleviation of N limitation by moderate concentrations of fertilization (20-80 kg ha(-1) year(-1)) promoted plant growth, but further N additions on top of the threshold level showed negative effects on plant growth. Growth responses of F. mandshurica seedlings to N addition of different concentrations were accompanied by corresponding changes in whole-plant hydraulic conductance; higher growth rate was accompanied by reduced whole-plant hydraulic conductance (Kplant) and higher leaf water-use efficiency. A detailed analysis on hydraulic conductance of different components of the whole-plant water transport pathway revealed that changes in root and leaf hydraulic conductance, rather than that of the stem, were responsible for Kplant responses to N fertilization. Both plant growth and hydraulic architecture responses to increasing levels of N addition were not linear, i.e., the correlation between measured parameters and N availability exhibited bell-shaped curves with peak values observed at medium levels of N fertilization. Changes in hydraulic architecture in response to fertilization found in the present study may represent an important underlying mechanism for the commonly observed changes in water-related tree performances in response to N deposition.

Isolation and Characterization of Three New Monoterpene Synthases from Artemisia annua.

Artemisia annua, an annual herb used in traditional Chinese medicine, produces a wealth of monoterpenes and sesquiterpenes, including the well-known sesquiterpene lactone artemisinin, an active ingredient in the treatment for malaria. Here we report three new monoterpene synthases of A. annua. From a glandular trichome cDNA library, monoterpene synthases of AaTPS2, AaTPS5, and AaTPS6, were isolated and characterized. The recombinant proteins of AaTPS5 and AaTPS6 produced multiple products with camphene and 1,8-cineole as major products, respectively, and AaTPS2 produced a single product, β-myrcene. Although both Mg2+ and Mn2+ were able to support their catalytic activities, altered product spectrum was observed in the presence of Mn2+ for AaTPS2 and AaTPS5. Analysis of extracts of aerial tissues and root of A. annua with gas chromatography–mass spectrometry detected more than 20 monoterpenes, of which the three enzymes constituted more than 1/3 of the total. Mechanical wounding induced the expression of all three monoterpene synthase genes, and transcript levels of AaTPS5 and AaTPS6 were also elevated after treatments with phytohormones of methyl jasmonate, salicylic acid, and gibberellin, suggesting a role of these monoterpene synthases in plant–environment interactions. The three new monoterpene synthases reported here further our understanding of molecular basis of monoterpene biosynthesis and regulation in plant.

Synthetic biology for production of natural and new-to-nature terpenoids in photosynthetic organisms.

With tens of thousands of characterized members, terpenoids constitute the largest class of natural compounds that are synthesized by all living organisms. Several terpenoids play primary roles in the maintenance of cell membrane fluidity, as pigments or as phytohormones, but most of them function as specialized metabolites that are involved in plant resistance to herbivores or plant-environment interactions. Terpenoids are an essential component of human nutrition, and many are economically important pharmaceuticals, aromatics and potential next-generation biofuels. Because of the often low abundance in their natural source, as well as the demand for novel terpenoid structures with new or improved bioactivities, terpenoid biosynthesis has become a prime target for metabolic engineering and synthetic biology projects. In this review we focus on the creation of new-to-nature or tailor-made plant-derived terpenoids in photosynthetic organisms, in particular by means of combinatorial biosynthesis and the activation of silent metabolism. We reflect on the characteristics of different potential photosynthetic host organisms and recent advances in synthetic biology and discuss their utility for the (heterologous) production of (novel) terpenoids.

Estructura del dosel y coeficientes de extinción teóricos en genotipos de café arábico en Colombia

<p>La estructura del dosel tiene un marcado efecto sobre la interceptación de la radiación y la fotosíntesis de la planta, además de otros procesos. El estudio se llevó a cabo en la Estación Central Naranjal de CENICAFÉ (Centro Nacional de Investigaciones de Café – Chinchiná, Caldas, Colombia) sobre 25 genotipos de Coffea arabica L., divididos en dos grupos. El primer grupo, con plantas de porte alto (3.6 años) y el segundo con plantas de porte bajo (2.6 años), ambos sembrados a una densidad de 5000 plantas.ha-1. La distribución de los ángulos de las hojas y las ramas en el dosel se caracterizaron en los diferentes genotipos evaluados, así mismo los coeficientes de extinción teóricos de la radiación solar directa y difusa fueron estimados. En los genotipos de porte alto predominaron las distribuciones foliares plagiófila y esférica, mientras que en los de porte bajo fue la planófila. El parámetro x representa a la distribución elipsoidal de los ángulos foliares, este valor varió entre 0.09 y 2.21 para los genotipos de porte alto (verticales y esféricos) y entre 1.90 y 3.98 para los de porte bajo (horizontales). Los coeficientes de extinción teóricos para la radiación directa derivados del parámetro x variaron entre 0.63 a 0.83 para el grupo de porte alto, mientras que en el porte bajo mostraron valores entre 0.84 a 0.93. Para la radiación difusa, los coeficientes presentaron la misma tendencia, pero con valores menores. En cuanto al ángulo de inclinación de las ramas, se caracterizó por ser predominantemente planófilo.</p>

Ecophysiology of leaf trichomes.

This review examines how leaf trichomes influence leaf physiological responses to abiotic environmental drivers. Leaf trichomes are known to modulate leaf traits, particularly radiation absorptance, but studies in recent decades have demonstrated that trichomes have a more expansive role in the plant-environment interaction. Although best known as light reflectors, dense trichome canopies modulate leaf heat balance and photon interception, and consequently affect gas exchange traits. Analysis of published studies shows that dense pubescence generally increases reflectance of visible light and near-infrared and infrared radiation. Reflective trichomes are also protective, reducing photoinhibition and UV-B related damage to leaf photochemistry. Little support exists for a strong trichome effect on leaf boundary layer resistance and transpiration, but recent studies indicate they may play a substantive role in leaf water relations affecting leaf wettability, droplet retention and leaf water uptake. Different lines of evidence indicate that adaxial and abaxial trichomes may function quite differently, even within the same leaf. Overall, this review synthesises and re-examines the diverse array of relevant studies from the past 40 years, illustrating our current understanding of how trichomes influence the energy, carbon and water balance of plants, and highlighting promising areas for future research.

Stratification of climate projections for efficient estimation of uncertainty and variation using weather-driven models

The range of uncertainties inherent in climate models can only be portrayed by provision of multiple climate projections. Unfortunately, such provision poses a challenge to model-based impact studies, since driving the relevant impact models using weather data from large numbers of climate projections may not be computationally feasible. Hence, it is important to investigate how to draw sub-samples of climate projections in a manner that reduces the subsequent computational burden. We describe a stratification-based protocol for sub-sampling climate projections to drive crop models with strata based on changes in mean temperature and changes in relative mean rainfall. As an example of the protocol's utility, simulated weather for each selected climate projection was used to drive 3 contrasting process-based models of plant-environment interactions to predict yields of spring barley, managed grassland, and short-rotation coppice. Many of the questions about potential impact that we wish to answer are related to variation in predicted yields. Variance components analyses of predicted yields for each of 2 time periods (2040s and 2080s) indicated that, after allowing for variability between grid squares, between 16 and 61% of the remaining variance in annual yields was uncertainty due to climate projections, the corresponding range for mean yields over 9 yr being from 63 to 93%. We found that our stratification procedure enhanced the precision in the estimate of the variance component due to climate projection, enabling reductions of up to 20% in the number of climate projections required to achieve equivalent precision compared to simple random sampling.

Allocation, stress tolerance and carbon transport in plants: how does phloem physiology affect plant ecology?

Despite the crucial role of carbon transport in whole plant physiology and its impact on plant-environment interactions and ecosystem function, relatively little research has tried to examine how phloem physiology impacts plant ecology. In this review, we highlight several areas of active research where inquiry into phloem physiology has increased our understanding of whole plant function and ecological processes. We consider how xylem-phloem interactions impact plant drought tolerance and reproduction, how phloem transport influences carbon allocation in trees and carbon cycling in ecosystems and how phloem function mediates plant relations with insects, pests, microbes and symbiotes. We argue that in spite of challenges that exist in studying phloem physiology, it is critical that we consider the role of this dynamic vascular system when examining the relationship between plants and their biotic and abiotic environment.

The Mediator complex subunits MED25/PFT1 and MED8 are required for transcriptional responses to changes in cell wall arabinose composition and glucose treatment in Arabidopsis thaliana.

BackgroundPlant cell walls are dynamic structures involved in all aspects of plant growth, environmental interactions and defense responses, and are the most abundant renewable source of carbon-containing polymers on the planet. To balance rigidity and extensibility, the composition and integrity of cell wall components need to be tightly regulated, for example during cell elongation.ResultsWe show that mutations in the MED25/PFT1 and MED8 subunits of the Mediator transcription complex suppressed the sugar-hypersensitive hypocotyl elongation phenotype of the hsr8-1 mutant, which has cell wall defects due to arabinose deficiency that do not permit normal cell elongation. This suppression occurred independently of light and jasmonic acid (JA) signaling. Gene expression analyses revealed that the expression of genes induced in hsr8-1 that encode enzymes and proteins that are involved in cell expansion and cell wall strengthening is reduced in the pft1-2 mutant line, and the expression of genes encoding transcription factors involved in reducing hypocotyl cell elongation, genes encoding cell wall associated enzymes and proteins is up-regulated in pft1-2. PFT1 was also required for the expression of several glucose-induced genes, including those encoding cell wall components and enzymes, regulatory and enzymatic components of anthocyanin biosynthesis, and flavonoid and glucosinolate biosynthetic pathways.ConclusionsThese results establish that MED25 and MED8 subunits of the Mediator transcriptional complex are required for the transcriptional regulation of genes involved in cell elongation and cell wall composition in response to defective cell walls and in sugar- responsive gene expression.Electronic supplementary materialThe online version of this article (doi:10.1186/s12870-015-0592-4) contains supplementary material, which is available to authorized users.

The soybean R2R3 MYB transcription factor GmMYB100 negatively regulates plant flavonoid biosynthesis.

Soybean flavonoids, a group of important signaling molecules in plant-environment interaction, ubiquitously exist in soybean and are tightly regulated by many genes. Here we reported that GmMYB100, a gene encoding a R2R3 MYB transcription factor, is involved in soybean flavonoid biosynthesis. GmMYB100 is mainly expressed in flowers, leaves and immature embryo, and its level is decreased after pod ripening. Subcellular localization assay indicates that GmMYB100 is a nuclear protein. GmMYB100 has transactivation ability revealed by a yeast functional assay; whereas bioinformatic analysis suggests that GmMYB100 has a negative function in flavonoid biosynthesis. GmMYB100-overexpression represses the transcript levels of flavonoid-related genes in transgenic soybean hairy roots and Arabidopsis, and inhibits isoflavonoid (soybean) and flavonol (Arabidopsis) production in transgenic plants. Furthermore, the transcript levels of six flavonoid-related genes and flavonoid (isoflavonoid and flavone aglycones) accumulation are elevated in the GmMYB100-RNAi transgenic hairy roots. We also demonstrate that GmMYB100 protein depresses the promoter activities of soybean chalcone synthase and chalcone isomerase. These findings indicate that GmMYB100 is a negative regulator in soybean flavonoid biosynthesis pathway.

Identification and characterization of microRNA expression in Ginkgo biloba L. leaves

Ginkgo biloba L., an extant primitive gymnosperm species, occupies an important position in the evolution of the plant kingdom. Furthermore, its leaves contain a large number of active, medicinally valuable compounds; therefore, it is also an important tree economically. MicroRNAs (miRNAs) are important regulators of gene expression implicated in controlling plant development and environmental interaction. Extensive studies of miRNAs have been performed in angiosperms, but no reports have focused on small RNAs in the basal gymnosperm G. biloba. Here, we used Illumina next-generation sequencing HiSeq™ 2000 platform to identify and quantitatively profile small RNAs in G. biloba leaves. A total of 13,414,548 and 12,293,511 reads, containing 202 and 201 known miRNAs, belonging to 82 and 78 families, were sequenced from two small RNA libraries constructed from female and male leaves, respectively. We also identified 174/174 novel miRNAs in the female/male leaves of G. biloba. Relative expression levels of the miRNAs and the precursor sequences of several of the known and novel miRNAs were further validated by subcloning and quantitative real-time PCR (qRT-PCR). Target predictions of the 380 and 340 known miRNAs, from female and male leaves, resulted in 2116 and 2002 target genes, while those of the 155 and 158 novel miRNAs resulted in 596 and 793 target genes, respectively. KEGG annotation analysis revealed that high-ranked miRNA-target genes are implicated in plant-pathogen interactions, plant hormone signal transduction, and flavonoid biosynthesis. Taken together, we identified a large number of miRNAs in mature female and male G. biloba leaves for the first time. We ascertained that the regulatory networks of the miRNAs are involved in many different primary biological processes based on potential target designations.

Influence of regional rainfall and Atlantic sea surface temperature on tree-ring growth of Poincianella pyramidalis, semiarid forest from Brazil

A tree-ring width chronology was developed from samples of thirteen Poincianella pyramidalis trees from the Caatinga semiarid region of northeastern Brazil, where the climate is characterized by marked seasonality in precipitation levels. Although a thin continuous marginal parenchyma band represents the limit of seasonal xylem production, and in spite of the presence of false rings, cross-dating is possible. In this sense, an interseries correlation of 0.572 was found indicating a considerable degree of consistency in the variability found among trees. Precipitation between January and July has a direct influence on growth, while a five month dry season interrupts the active division of cambial cells. A significant positive correlation was also found between sea surface temperatures (SSTs) in the tropical Atlantic and tree growth, but with a lag of six months. As the rainfall regime of northeastern Brazil presents a great deal of inter-annual variability due to fluctuations in global factors such as the SSTs of the tropical Atlantic and the intertropical convergence zone, the close relationship observed between P. pyramidalis tree growth and regional climate fluctuations appears as a logical plant-environment interaction that can be used as a reliable parameter for dendroecological inferences on tree growth dynamics and the reconstructions of past droughts in the Caatinga region.

Large-Scale Evolutionary Analysis of Genes and Supergene Clusters from Terpenoid Modular Pathways Provides Insights into Metabolic Diversification in Flowering Plants.

An important component of plant evolution is the plethora of pathways producing more than 200,000 biochemically diverse specialized metabolites with pharmacological, nutritional and ecological significance. To unravel dynamics underlying metabolic diversification, it is critical to determine lineage-specific gene family expansion in a phylogenomics framework. However, robust functional annotation is often only available for core enzymes catalyzing committed reaction steps within few model systems. In a genome informatics approach, we extracted information from early-draft gene-space assemblies and non-redundant transcriptomes to identify protein families involved in isoprenoid biosynthesis. Isoprenoids comprise terpenoids with various roles in plant-environment interaction, such as pollinator attraction or pathogen defense. Combining lines of evidence provided by synteny, sequence homology and Hidden-Markov-Modelling, we screened 17 genomes including 12 major crops and found evidence for 1,904 proteins associated with terpenoid biosynthesis. Our terpenoid genes set contains evidence for 840 core terpene-synthases and 338 triterpene-specific synthases. We further identified 190 prenyltransferases, 39 isopentenyl-diphosphate isomerases as well as 278 and 219 proteins involved in mevalonate and methylerithrol pathways, respectively. Assessing the impact of gene and genome duplication to lineage-specific terpenoid pathway expansion, we illustrated key events underlying terpenoid metabolic diversification within 250 million years of flowering plant radiation. By quantifying Angiosperm-wide versatility and phylogenetic relationships of pleiotropic gene families in terpenoid modular pathways, our analysis offers significant insight into evolutionary dynamics underlying diversification of plant secondary metabolism. Furthermore, our data provide a blueprint for future efforts to identify and more rapidly clone terpenoid biosynthetic genes from any plant species.

Species specific and environment induced variation of δ(13)C and δ(15)N in alpine plants.

Stable carbon and nitrogen isotope signals in plant tissues integrate plant-environment interactions over long periods. In this study, we hypothesized that humid alpine life conditions are narrowing the scope for significant deviations from common carbon, water and nitrogen relations as captured by stable isotope signals. We explored the variation in δ13C and δ15N in 32 plant species from tissue type to ecosystem scale across a suite of locations at c. Two thousand five hundred meter elevation in the Swiss Alps. Foliar δ13C and δ15N varied among species by about 3–4‰ and 7–8‰ respectively. However, there was no overall difference in means of δ13C and δ15N for species sampled in different plant communities or when bulk plant dry matter harvests of different plant communities were compared. δ13C was found to be highly species specific, so that the ranking among species was mostly maintained across 11 habitats. However, δ15N varied significantly from place to place in all species (a range of 2.7‰) except in Fabaceae (Trifolium alpinum) and Juncaceae (Luzula lutea). There was also a substantial variation among individuals of the same species collected next to each other. No difference was found in foliar δ15N of non-legumes, which were either collected next to or away from the most common legume, T. alpinum. δ15N data place Cyperaceae and Juncaceae, just like Fabaceae, in a low discrimination category, well separated from other families. Soil δ15N was higher than in plants and increased with soil depth. The results indicate a high functional diversity in alpine plants that is similar to that reported for low elevation plants. We conclude that the surprisingly high variation in δ13C and δ15N signals in the studied high elevation plants is largely species specific (genetic) and insensitive to obvious environmental cues.

Are betalain pigments the functional homologues of anthocyanins in plants?

Betalains, a small group of alkaloid pigments restricted to certain families of the Caryophyllales, have comparable optical properties and share similar histological locations in vegetative tissues with those of the more abundant anthocyanins. It has long been speculated that the two pigments are functional homologues in plant-environment interactions. Recent empirical evidence indicates that anthocyanins and betacyanins are both effective photoprotectants, are associated with increased tolerance to drought and salinity stress, and are efficient scavengers of reactive oxygen species in plants facing a variety of abiotic stressors. Nevertheless, the capacity of betalains to maintain a red colour irrespective of changes in vacuolar pH, their enhanced absorptivity of visible wavelengths, and their strong association with vacuolar ATPase activity, suggest that they may confer adaptive benefits not found in those species that produce anthocyanins. There remains much to be learned about the functional significance of betalains.

Multiple functional roles of anthocyanins in plant-environment interactions

Almost a century after Muriel Wheldale’s landmark publication, “The Anthocyanin Pigments of Plants” (Wheldale, 1916), much about anthocyanin function in plants remains to be elucidated, even though the environmental drivers and biosynthetic pathways leading to anthocyanin production are well established. That anthocyanins may protect leaves in plants facing biotic or abiotic stressors, an idea dating back to Pringsheim (1879), is arguably the most widely accepted function for foliar anthocyanins, although the mechanism(s) by which they could mitigate effects of stress remains heatedly debated. In addition to the most frequently discussed putative roles of anthocyanins as antioxidants and sunscreens, other less-explored possibilities might equally serve to ameliorate plant function under, for example, under conditions of mineral imbalance. In particular: (i) anthocyanins may serve as metal-chelating agents under conditions of excess edaphic metal ions and (ii) anthocyanin accumulation might delay foliar senescence, which is otherwise usually accelerated in plants growing under macronutrient deficiency. The latter mechanism might be particularly advantageous to prolong plant survival and increase the possibility of reproductive success.

The role of cis-zeatin-type cytokinins in plant growth regulation and mediating responses to environmental interactions.

Cytokinins (CKs) are well-established as important phytohormonal regulators of plant growth and development. An increasing number of studies have also revealed the function of these hormones in plant responses to biotic and abiotic stresses. While the function of certain CK classes, including trans-zeatin and isopentenyladenine-type CKs, have been studied in detail, the role of cis-zeatin-type CKs (cZs) in plant development and in mediating environmental interactions is less well defined. Here we provide a comprehensive summary of the current knowledge about abundance, metabolism and activities of cZs in plants. We outline the history of their analysis and the metabolic routes comprising cZ biosynthesis and degradation. Further we provide an overview of changes in the pools of cZs during plant development and environmental interactions. We summarize studies that investigate the role of cZs in regulating plant development and defence responses to pathogen and herbivore attack and highlight their potential role as 'novel' stress-response markers. Since the functional roles of cZs remain largely based on correlative data and genetic manipulations of their biosynthesis, inactivation and degradation are few, we suggest experimental approaches using transgenic plants altered in cZ levels to further uncover their roles in plant growth and environmental interactions and their potential for crop improvement.

Volatile organic compounds as non-invasive markers for plant phenotyping.

Plants emit a great variety of volatile organic compounds (VOCs) that can actively participate in plant growth and protection against biotic and abiotic stresses. VOC emissions are strongly dependent on environmental conditions; the greatest ambiguity is whether or not the predicted change in climate will influence and modify plant-pest interactions that are mediated by VOCs. The constitutive and induced emission patterns between plant genotypes, species, and taxa are highly variable and can be used as pheno(chemo)typic markers to distinguish between different origins and provenances. In recent years significant progress has been made in molecular and genetic plant breeding. However, there is actually a lack of knowledge in functionally linking genotypes and phenotypes, particularly in analyses of plant-environment interactions. Plant phenotyping, the assessment of complex plant traits such as growth, development, tolerance, resistance, etc., has become a major bottleneck, and quantitative information on genotype-environment relationships is the key to addressing major future challenges. With increasing demand to support and accelerate progress in breeding for novel traits, the plant research community faces the need to measure accurately increasingly large numbers of plants and plant traits. In this review article, we focus on the promising outlook of VOC phenotyping as a fast and non-invasive measure of phenotypic dynamics. The basic principle is to define plant phenotypes according to their disease resistance and stress tolerance, which in turn will help in improving the performance and yield of economically relevant plants.

Combined Effects of Elevated Carbon Dioxide and K and Mg Deficiencies on Wheat Plants

We are facing climate change that is affecting world ecosystem substantially and we need to investigate its effects for the sake of protection and mitigation. According to different IPCC scenarios based on possible emission levels, atmospheric [CO2] which is currently around 400μmol mol-1 will rise to 421-936μmol mol-1 by the end of this century unless a strict greenhouse gas mitigation strategy is put forward on global scale (IPCC, 2013). While there are numerous studies on the effects of climate change and rising [CO2] to the plants, it is still not clear how exactly plants respond to this change. The plant-environment interaction consisting very complex facts is the main reason of this challenge. One of the most crucial parts of this is to understand the combined effects of nutrient availabilities and elevated CO2 levels.Durum wheat (Triticum durum, Saricanak 98) and bread wheat (Triticum aestivum, Adana 99) plants were grown with adequate Mg-K and low Mg (75 and 150μM) and low K (10 and 30μM) supply in nutrient solution and under three different CO2 conditions (ambient: 400μmol mol-1, elevated: 600 and 900μmol mol-1). When plants were twenty days old gas exchange parameters (using LI-6400 XT, LI-COR Biosciences, Inc. Lincoln, Nebraska, USA), chlorophyll content (using chlorophyll meter SPAD-502, Konica Minolta Sensing Europe B.V.) and specific weight were measured in the second oldest leaves.While shoot and root dry weight was increasing with elevating [CO2] in adequate Mg and K plants, there was a decrement or a very slight increment in Mg and K deficiency treated plants. Photosynthesis rate (μmol CO2 m-2 s-1) increased 18% and 19.6% in Sarıçanak 98 and 15.7% and %15.3 in Adana 99 plants with 600 and 900ppm CO2 treatments respectively in the adequate Mg and K treatments, whereas although there was some increment in Mg and K deficient plants with [CO2] elevation it was not important since overall photosynthesis rates were low in these plants in all three [CO2] treatments. Leaf specific weight was much higher in Mg and K deficient plants compare to adequate Mg and K plants which may correspond possible defects in carbohydrate partitioning. Especially in Sarıçanak 98, Mg and K deficient plants specific weight was increasing with the increasing [CO2]. Adana 99 plants showed the same trend although it was not as significant as in Sarıçanak 98 plants.With emphasizing adequate Mg and K nutrition requirement to maintain high photosynthetic efficiency and a balanced export of photo-assimilates to sink organs (Marschner, 1995; Cakmak and Kirkby, 2008), this study points out that this can be even more important under elevated [CO2].This study was supported by TUBITAK (Project no. 113Z129).

Urbanisation, plant traits and the composition of urban floras

Given the increasing prevalence of cities, a better mechanistic and functional understanding of plant responses to urbanisation will assist biodiversity conservation and the provision of ecosystem services. Plant functional traits offer an opportunity to do this. To explore the relationship between plant traits and the urban environment, we synthesised the results of 29 studies that specifically examined plant traits or niche indicators (e.g. Ellenberg numbers) of urban floras. Niche indicators for nutrients, temperature and alkalinity were found to consistently increase across many studies. Some plant traits (e.g. woodiness, seed mass and height) tended to increase in response to urbanisation, while other traits have mixed responses and many other traits are understudied. We propose that variability in the observed responses is linked to the consistency and strength of urban stressors acting on those traits, and the importance of local factors. Our synthesis highlights the complexity of urban plant–environment interactions with many traits influenced by multiple abiotic, biotic and disturbance effects of urbanisation. Multiple stressors make it difficult to detect trends in urban plant trait signatures unless one urban stressor drives a particularly strong response or multiple stressors act on the response in the same direction. While our review has developed a better understanding of how urbanisation may assemble urban floras, further advances can be gained through studies that focus on specific urbanisation processes, measurable morphological traits and data curation and analyses that facilitate meta-analysis.