Urbanization alters plastic responses in the common dandelion Taraxacum officinale (original) (raw)
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Biological Invasions, 2010
Ecological theory predicts a positive association between environmental heterogeneity of a given habitat and the magnitude of phenotypic plasticity exhibited by resident plant populations. Taraxacum officinale (dandelion) is a perennial herb from Europe that has spread worldwide and can be found growing in a wide variety of habitats. We tested whether T. officinale plants from a heterogeneous environment in terms of water availability show greater phenotypic plasticity and better performance in response to experimental water shortage than plants from a less variable environment. This was tested at both low and moderate temperatures in plants from two sites (Corvallis, Oregon, USA, and El Blanco, Balmaceda, Chile) that differ in their pattern of monthly variation in rainfall during the growth season. We compared chlorophyll fluorescence (photosynthetic performance), flowering time, seed output, and total biomass. Plants subjected to drought showed delayed flowering and lower photosynthetic performance. Plants from USA, where rainfall variation during the growth season was greater, exhibited greater plasticity to water shortage in photosynthetic performance and flowering time than plants from Chile. This was true at both low and moderate temperatures, which were similar to early-and lateseason conditions, respectively. However, phenotypic plasticity to decreased water availability was seemingly maladaptive because under both experimental temperatures USA plants consistently performed worse than Chile plants in the low water environment, showing lower total biomass and fewer seeds per flower head. We discuss the reliability of environmental clues for plasticity to be adaptive. Further research in the study species should include other plant traits involved in functional responses to drought or potentially associated with invasiveness.
New Phytologist, 2005
• We compared plastic responses to variation in the light environment for sympatric populations of native and exotic dandelion species, Taraxacum ceratophorum and Taraxacum officinale. • Plasticity in leaf size, inflorescence height, reproductive phenology and dispersalrelated traits were measured under experimentally altered light quality (red : far-red light ratio, R : FR) and light intensity (photosynthetically active radiation, PAR). To test whether differences in means and reaction norms of dispersal-related traits between species affected colonization potential, we created seed-dispersal models based on seed-fall rate and release height. • Differences in plasticity between species were not systematic, but varied in direction and magnitude among traits. Taraxacum officinale produced larger leaves that exhibited greater plasticity in size under variable light intensity than T. ceratophorum. Plasticity in scape length at flowering occurred in relation to R : FR ratio in both species, but tended to be greater in T. ceratophorum. Seed-bearing scapes of T. officinale were taller and more canalized in height across light regimes than scapes of T. ceratophorum. Seeds of T. officinale were smaller than seeds of T. ceratophorum. • Models predict greater dispersal in T. officinale within open and vegetated habitats. In contrast to the idea that plasticity promotes invasiveness, results suggest that the lack of plasticity in dispersal-related traits enhances the colonization potential of T. officinale .
Plastic in the Environment: A Modern Type of Abiotic Stress for Plant Physiology
Plants
In recent years, plastic pollution has become a growing environmental concern: more than 350 million tons of plastic material are produced annually. Although many efforts have been made to recycle waste, a significant proportion of these plastics contaminate and accumulate in the environment. A central point in plastic pollution is demonstrated by the evidence that plastic objects gradually and continuously split up into smaller pieces, thus producing subtle and invisible pollution caused by microplastics (MP) and nanoplastics (NP). The small dimensions of these particles allow for the diffusion of these contaminants in farmlands, forest, freshwater, and oceans worldwide, posing serious menaces to human, animal, and plant health. The uptake of MPs and NPs into plant cells seriously affects plant growth, development, and photosynthesis, finally limiting crop yields and endangering natural environmental biodiversity. Furthermore, nano- and microplastics—once adsorbed by plants—can eas...
Urban plant physiology: adaptation-mitigation strategies under permanent stress
Trends in plant science, 2015
Urban environments that are stressful for plant function and growth will become increasingly widespread in future. In this opinion article, we define the concept of 'urban plant physiology', which focuses on plant responses and long term adaptations to urban conditions and on the capacity of urban vegetation to mitigate environmental hazards in urbanized settings such as air and soil pollution. Use of appropriate control treatments would allow for studies in urban environments to be comparable to expensive manipulative experiments. In this opinion article, we propose to couple two approaches, based either on environmental gradients or manipulated gradients, to develop the concept of urban plant physiology for assessing how single or multiple environmental factors affect the key environmental services provided by urban forests.
Biological Invasions, 2012
Phenotypic plasticity has long been suggested to facilitate biological invasions in changing environments, allowing a species to maintain a good ecophysiological performance. High-mountain habitats have been particularly useful for evaluation of the relative importance of environmental conditions in the colonization and invasion process, because they have heterogeneous and stressful climatic conditions, inducing photoinhibition. Light intensity is one of the most changing conditions along altitudinal gradients, showing more variability in higher altitudes. In this study, we analyzed the plasticity in photoprotective strategies and performance of the invasive Taraxacum officinale. Additionally, we tested whether higher plasticity enhances competitive ability in an alpine environment We conducted an experiment to evaluate plasticity with a second generation (F2) of T. officinale individuals from 1,600 to 3,600 m, in a greenhouse with variation in light intensity. Treatments consisted of transferring 120 individuals from each altitude to two conditions of light intensity. We then recorded concentrations of photoprotection pigment, de-epoxidation state of the xanthophyll cycle, foliar angles, photochemical efficiency by fluorescence of photosystem II, total dry biomass and flower production. Additionally, we compared plasticity in both photoprotective and performance traits between T. officinale and the co-occurring native species Hypochaeris thrincioides. Finally, we performed a manipulative experiment under two light regimes in order to assess the competitive outcome between the invasive T. officinale and the native H. thrincioides. Individuals from higher altitude showed significantly greater plasticity than individuals from lower altitude. Similarly, individuals under high light intensity showed higher levels of photoprotective pigments, biomass and flower production. On the other hand, the invasive plant species showed significantly greater plasticity than the co-occurring native species, and a strong negative impact on the biomass of the native plant. Phenotypic plasticity seems to be a successful strategy in T. officinale to compete with native species and may be positively associated with the success of invasions, being greater in individuals from more heterogeneous and stressful environments.
Plant and Soil, 2010
Common dandelions (Taraxacum officinale Weber, sensu lato; Asteraceae) introduced to North America form an assemblage of asexual (agamospermous), clonal lineages derived from Eurasian mixed sexual and asexual populations. We investigated whether selection for more pollution tolerant clonal lineages occurs at polluted sites and selection for more pollution intolerant lineages occurs at unpolluted sites. We tested the above hypothesis by performing reciprocal greenhouse productivity experiments in which unique dandelion clones (12 clones, identified by DNA fingerprinting, from each site type) sampled from two unpolluted and two polluted (moderately enhanced Cu, Pb and Zn soil concentrations) sites were grown pairwise in both unpolluted (nutrient solution only) and polluted (nutrient solution + Cu, Pb and Zn) media (n=48 paired tests for each media type). Dandelion clones from polluted sites produced fewer and smaller leaves, shorter roots and smaller root diameters, reduced shoot and root dry weights, and reduced total biomass compared to clones from unpolluted sites when clones were grown in unpolluted-media (P≤0.05). In contrast, clones taken from unpolluted sites were shown to produce significantly fewer and shorter leaves, shorter roots and smaller root diameters, reduced shoot and root dry weights, reduced total biomass, a reduced shoot : root biomass ratio, and have much lower survival compared to clones from polluted sites when both were grown in polluted-media (P≤0.05). These results reveal that there was increased selection against unpolluted-site clonal lineages in polluted-media and against polluted-site clonal lineages in unpolluted-media. Across all treatments, clones from unpolluted sites growing in unpolluted-media had the highest proximate measures of fitness. Overall, these findings provide insight into the relationships among anthropogenic environmental contamination and the consequent effects of selective forces acting on dandelion clones and their population genetic architecture.
Water, Air, & Soil Pollution, 2015
Physiological and biochemical characteristics were evaluated in dandelion plants (Taraxacum officinale) growing naturally in an urban environment. The study area was located in Pisa, Italy, and 27 sites in the municipality were chosen to assess the biochemical and physiological features of dandelion plants and the trace metal content in the urban soil. Concentrations of elements including, Cr, Cu, Mn and Zn were analysed in the soil together with dandelion shoot and root tissues collected from the various sites. Chlorophyll a fluorescence analysis, the pigment content, antioxidant power and phenol content were determined in dandelion. The results showed very limited soil pollution due to trace metals in the urban sites. However, dandelion showed Zn uptake and translocation although no damage was observed in the plants. Our results highlight that dandelion plants are able to survive in a constrained environment thanks to the high phenol content which is effective in combatting the oxidative stress induced by heavy metals.
Environmental Monitoring and Assessment, 2005
Assessing the genetic structure of natural populations differentially impacted by anthropogenic contaminants can be a useful tool for evaluating the population genetic consequences of exposure to pollution. In this study, measures of genetic diversity at variable-number-tandem-repeat loci in six dandelion populations (3 urban and 3 rural) showed patterns that may have been influenced by exposure to environmental contaminants. Mean genetic similarity among individuals within a population was significantly and positively correlated with increasing levels of airborne particulate matter (< or = 10 microm, PM10) and soil concentrations of four metals (Cd, Fe, Ni and Pb). In addition, mean genetic similarity was always significantly higher at the urban sites compared to rural sites. There was a significant negative correlation between the number of genotypes at a site and increasing amounts of PM10, concentrations of five soil metals (Cd, Cu, Fe, Ni and Pb), leaf tissue levels of Fe and a significant positive correlation between the extent of clonality at a site and levels of PM10 and soil concentrations of five metals (Cd, Cu, Fe, Ni and Pb). Although, this study does not directly establish a causal link between the specific contaminants detected at the study sites and differences in genetic diversity, our data are consistent with the hypothesis that pollution-induced selection has contributed in some fashion to the lower genetic diversity found at the urban sites.