Drought responses,phenotypic plasticity and survival of Mediterranean species in two different microclimatic sites

• Climate models predict a further drying of the Mediterranean summer. One way for plant species to persist during such climate changes is through acclimation. Here, we determine the extent to which trait plasticity in response to drought differs between species and between sites, and address the question whether there is a trade‐off between drought survival and phenotypic plasticity.
• Throughout the summer we measured physiological traits (photosynthesis – A_max, stomatal conductance – g_s, transpiration – E, leaf water potential – ψl) and structural traits (specific leaf area – SLA, leaf density – LD, leaf dry matter content – LDMC, leaf relative water content – LRWC) of leaves of eight woody species in two sites with slightly different microclimate (north‐ versus south‐facing slopes) in southern Spain. Plant recovery and survival was estimated after the summer drought period.
• We found high trait variability between species. In most variables, phenotypic plasticity was lower in the drier site. Phenotypic plasticity of SLA and LDMC correlated negatively with drought survival, which suggests a trade‐off between them. On the other hand, high phenotypic plasticity of SLA and LDMC was positively related to traits associated with rapid recovery and growth after the drought period.
• Although phenotypic plasticity is generally seen as favourable during stress conditions, here it seemed beneficial for favourable conditions. We propose that in environments with fluctuating drought periods there can be a trade‐off between drought survival and growth during favourable conditions. When climate become drier, species with high drought survival but low phenotypic plasticity might be selected for.

     

Phenotypic plasticity rather than locally adapted ecotypes allows the invasive alligator weed to colonize a wide range of habitats

Both phenotypic plasticity and locally adapted ecotypes may contribute to the success of invasive species in a wide range of habitats. Here, we conducted common garden experiments and molecular marker analysis to test the two alternative hypotheses in invasive alligator weed (Alternanthera philoxeroides), which colonizes both aquatic and terrestrial habitats. Ninety individuals from three pairs of aquatic versus terrestrial populations across southern China were analyzed, using inter simple sequence repeat (ISSR) marker, to examine population differentiation in neutral loci. Two common gardens simulating aquatic and terrestrial habitats were set up to examine population differentiation in quantitative traits. We found no evidence of population differentiation in both neutral loci and quantitative traits. Most individuals shared the same ISSR genotype. Meanwhile, plants from different habitats showed similar reaction norms across the two common gardens. In particular, plants allocated much more biomass to the belowground roots in the terrestrial environment, where alligator weed may lose part or all of the aboveground shoots because of periodical or accidental disturbances, than those in the aquatic environment. The combined evidence from molecular marker analysis and common garden experiments support the plasticity hypothesis rather than the ecotype hypothesis in explaining the adaptation of alligator weed in a wide range of habitats.     

异质生境中水生植物表型可塑性的研究进展

水生植物是一类以草本植物为主、与水紧密相关的生态类群, 大多数具有克隆性。面对水环境的变化, 水生植物在形态、行为和生理上表现出多样化的表型可塑性, 对异质生境具有很强的适应能力。表型可塑性研究已在陆生植物的多个类群展开, 然而目前对异质生境下水生植物的生态适应对策, 尤其是表型可塑性的研究尚重视不够。本文在阐明克隆植物表型可塑性主要实现方式及其关系、水生环境异质性及其特点的基础上, 重点从形态可塑性、觅食行为、克隆整合、克隆分工和风险分摊等5个方面讨论了水生植物如何通过表型可塑性适应异质性水生环境。在今后的水生植物表型可塑性研究中, 建议着重探讨以下问题: (1)表型可塑性的变化规律及机理; (2)克隆整合对群落和生态系统的影响; (3)克隆整合与克隆片段化的权衡; (4)不同克隆构型的表型可塑性及其内在机制; (5)表型可塑性的适应性进化; (6)水生植物与其他类群/营养级物种的关系; (7)水生生态系统对全球变化的响应。     

Drought response of two bedding plants

Bedding plants are an important part of the urban public space and private gardens. However, they are not always properly watered and suffer from drought stress, especially when grown in containers. In this trial a response to water stress of two commonly used species, impatiens (Impatiens walleriana Hook) and geranium (Pelargonium hortorum L. H. Bailey) were compared. The former is highly herbaceous and prone to wilting whereas the latter has hairy leaves and is better adapted to drought. Plants were grown at three levels of soil water content (SWC): 80% (control), 60% (mild stress) and 30% (severe stress). Drought was maintained during three 10 day cycles, separated by 10 day periods of normal watering. In both species roots were significantly longer in plants grown at 30% SWC as compared to 80% SWC while plant height and flower number were reduced by drought only in impatiens. The initial relative water content (RWC) was lower in geranium and decreased less in response to drought than in impatiens. Ammonium content in leaves of both species increased significantly under stress but the ranges of increase were different in both species. There was a significant increase in the free amino acids content in leaves of impatiens as compared to geranium but this rise was more time than drought dependent. The reduction in the a + b chlorophyll concentration in leaves of impatiens was significantly time and stress dependent while no reaction in geranium was observed. The above results show that changes in leaf RWC merit further attention as a possible indicator of plant response to drought stress in ornamental plants but additional studies are needed before this or other parameters can be used to evaluate new bedding plants for introduction into urban growing conditions, or as selection criteria in breeding for adaptation to demanding growing conditions.     

Desiccation of sediments affects assimilate transport within aquatic plants and carbon transfer to microorganisms

• With the projected increase in drought duration and intensity in future, small water bodies, and especially the terrestrial–aquatic interfaces, will be subjected to longer dry periods with desiccation of the sediment. Drought effects on the plant–sediment microorganism carbon continuum may disrupt the tight linkage between plants and microbes which governs sediment carbon and nutrient cycling, thus having a potential negative impact on carbon sequestration of small freshwater ecosystems. However, research on drought effects on the plant–sediment carbon transfer in aquatic ecosystems is scarce. We therefore exposed two emergent aquatic macrophytes, Phragmites australis and Typha latifolia, to a month‐long summer drought in a mesocosm experiment.
• We followed the fate of carbon from leaves to sediment microbial communities with ¹³CO₂ pulse labelling and microbial phospholipid‐derived fatty acid (PLFA) analysis.
• We found that drought reduced the total amount of carbon allocated to stem tissues but did not delay the transport. We also observed an increase in accumulation of ¹³C‐labelled sugars in roots and found a reduced incorporation of ¹³C into the PLFAs of sediment microorganisms.
• Drought induced a switch in plant carbon allocation priorities, where stems received less new assimilates leading to reduced starch reserves whilst roots were prioritised with new assimilates, suggesting their use for osmoregulation. There were indications that the reduced carbon transfer from roots to microorganisms was due to the reduction of microbial activity via direct drought effects rather than to a decrease in root exudation or exudate availability.

     

Transgenerational plasticity in Silene vulgaris in response to three types of stress

• The environment experienced by plants can influence the phenotype of their offspring. Such transgenerational plasticity can be adaptive when it results in higher fitness of the offspring under conditions correlated with those experienced by the mother plant. However, it has rarely been tested if such anticipatory parental effects may be induced with different environments.
• We grew clonal replicates of Silene vulgaris under control conditions and three types of stress (nutrient deficiency, copper addition and drought), which are known from natural populations of the species. We then subjected offspring from differently treated mother plants to each of the different stress treatments to analyse the influence of maternal and offspring environment on performance and several functional traits.
• Current stress treatments strongly influenced biomass and functional traits of the plants, mostly in line with responses predicted by the theory of functional equilibrium. Plant performance was also influenced by maternal stress treatments, and some effects independent of initial size differences remained until harvest. In particular, stressed mothers produced offspring of higher fitness than control plants. However, there was no evidence for treatment‐specific adaptive transgenerational plasticity, as offspring from a mother plant that had grown in a specific environment did not grow better in that environment than other plants.
• Our results indicate that the maternal environment may affect offspring traits and performance, but also that this transgenerational plasticity is not necessarily adaptive.

     

Species‐specific differences in water uptake depth of mature temperate trees vary with water availability in the soil

• Temperate tree species differ in their physiological sensitivity to declining soil moisture and drought. Although species‐specific responses to drought have often been suggested to be the result of different water uptake depths, empirical evidence for such a mechanism is scarce.
• Here we test if differences in water uptake depths can explain previously observed species‐specific physiological responses of temperate trees to drought and if the water uptake depth of different species varies in response to declining soil moisture. For this purpose, we employed stable oxygen and hydrogen isotopes of soil and xylem water that we collected over the course of three growing seasons in a mature temperate forest in Switzerland.
• Our data show that all investigated species utilise water from shallow soil layers during times of sufficient soil water supply. However, Fraxinus excelsior, Fagus sylvatica and Acer pseudoplatanus were able to shift their water uptake to deeper soil layers when soil water availability decreased in the topsoil. In contrast, Picea abies, was not able to shift its water uptake to deeper soil layers.
• We conclude from our data that more drought‐resistant tree species are able to shift their water uptake to deeper soil layers when water availability in the topsoil is becoming scarce. In addition, we were able to show that water uptake depth of temperate tree species is a trait with high plasticity that needs to be characterised across a range of environmental conditions.

     

Latitudinal trait variation and responses to drought in Arabidopsis lyrata

Species may respond in three ways to environmental change: adapt, migrate, or go extinct. Studies of latitudinal clines can provide information on whether species have adapted to abiotic stress such as temperature and drought in the past and what the traits underlying adaptation are. We investigated latitudinal trait variation and response to drought in North American populations of Arabidopsis lyrata. Plants from nine populations collected over 13° latitude were grown under well-watered and dry conditions. A total of 1,620 seedlings were raised and 12 phenological, physiological, morphological, and life history traits were measured. Two traits, asymptotic rosette size and the propensity to flower, were significantly associated with latitude: plants from northern locations grew to a larger size and were more likely to flower in the first season. Most traits displayed a plastic response to drought, but plasticity was never related linearly with latitude nor was it enhanced in populations from extreme latitudes with reduced water availability. Populations responded to drought by adopting mixed strategies of resistance, tolerance, and escape. The study shows that latitudinal adaptation in A. lyrata involves the classic life history traits, size at and timing of reproduction. Contrary to recent theoretical predictions, adaptation to margins is based on fixed trait differences and not on phenotypic plasticity, at least with respect to drought.     

Morphology and adaptation of aquatic mosses in an Antarctic lake

Abstract

Two species of moss growing in Moss Lake on Signy Island, South Orkney Islands, had unusual morphologies with large leaves and long internodes. Both Calliergon sarmentosum and Drepanocladus cf. aduncus differed from their terrestrial counterparts and from each other in the character of their leaves. The two genera differed in the ability of the terrestrial forms to develop a large-leaved growth form. Calliergon, which was represented by the same species in both environments, changed to the aquatic morphology when separated shoots were grown either submerged or under damp conditions. Ught intensity was not an important factor influencing change in morphology. In contrast, terrestrial Drepanocladus uncinatus, the closest taxonomic counterpart of D. cf. aduncus on Signy Island, did not show any adaptation under similar conditions. The aquatic forms also showed a corresponding degree of plasticity in their natural habitat. Calliergon varied from robust shoots to microphyllous or even leafless stems whereas Drepanocladus cf. aduncus only grew in the robust form. These differences were related to the success of the two species at different depths and it is suggested that the very low compensation points of the two mosses (reported in a separate study) resulted from the morphology of the plants.     

Decrypting stable‐isotope (δ13C and δ15N) variability in aquatic plants

相似文献   

Growth rates and morphological adaptations of aquatic and terrestrial forms of amphibious Littorella uniflora (L.) Aschers.

Morphological – anatomical features of the terrestrial and the aquatic life form of the rosette species Littorella uniflora, inhabiting nutrient poor soils of oligotrophic lakes, were investigated together with growth rates of both life forms and of transplants. Growth rates were the same for the two life forms. However, growth of transplanted plants was somewhat reduced by transition from one environment to another. This was especially true for aquatic plants, which may be stressed by desiccation when moved to the terrestrial environment. The morphological – anatomical differences between the life forms were small compared with many other amphibious species which produce highly specialized leaves and life forms in air and under water. It is suggested that the conservative leaf morphology of Littorella is a consequence of the high dependence on rhizospheric CO₂ of both the aquatic and the terrestrial form of Littorella, making production of leaves specialized for carbon uptake in one specific environment unnecessary.     

Phenotypic plasticity as a clue for invasion success of the submerged aquatic plant Elodea nuttallii

• Two closely related alien submerged aquatic plants were introduced into Europe. The new invader (Elodea nuttallii) gradually displaced E. canadensis even at sites where the latter was well established. The aim of the study was to evaluate the combined effects of environmental factors on several phenotypic characteristics of the two Elodea species, and to relate these phenotypic characteristics to the invasion success of E. nuttallii over E. canadensis.
• In a factorial design, Elodea plants were grown in aquaria containing five different nitrogen concentrations and incubated at five different light intensities. We used six functional traits (apical shoot RGR), total shoot RGR, relative elongation, root length, lateral spread, branching degree) to measure the environmental response of the species. We calculated plasticity indices to express the phenotypic differences between species.
• Light and nitrogen jointly triggered the development of phenotypic characteristics that make E. nuttallii a more successful invader in eutrophic waters than E. canadensis. The stronger invader showed a wider range of phenotypic plasticity. The apical elongation was the main difference between the two species, with E. nuttallii being more than two times longer than E. canadensis. E. canadensis formed dense side shoots even under high shade and low nitrogen levels, whereas E. nuttallii required higher light and nitrogen levels.
• We found that under more eutrophic conditions, E. nuttallii reach the water surface sooner than E. canadensis and through intensive branching outcompetes all other plants including E. canadensis. Our findings support the theory that more successful invaders have wider phenotypic plasticity.

     

Phenotypic variation and water selection potential in the stem structure of invasive alligator weed

The morphological and anatomical characteristics of stems have been found to be related to drought resistance in plants. Testing the phenotypic selection of water availability on stem anatomical traits would be useful for exploring the evolutionary potential of the stem in response to water availability. To test the phenotypic variation of the stem anatomical traits of an invasive plant in response to water availability, we collected a total of 320 individuals of Alternanthera philoxeroides from 16 populations from terrestrial and aquatic habitats in 8 plots in China and then analyzed the variation, differentiation, plasticity and selection potential of water availability on the stem anatomical traits. We found that except for the thickness of the cortex, all of the examined phenotypic parameters of the A. philoxeroides stem were significantly and positively correlated with soil water availability. The phenotypic differentiation coefficient for all of the anatomical structural parameters indicated that most of the variation existed between habitats within the same plot, whereas there was little variation among plots or among individuals within the same habitat except for variation in the thickness of the cortex. A significant phenotypic plasticity response to water availability was found for all of the anatomical traits of A. philoxeroides stem except for the thickness of the cortex. The associations between fitness and some of the anatomical traits, such as the stem diameter, the cortex area-to-stem area ratio, the pith cavity area-to-stem area ratio and the density of vascular bundles, differed with heterogeneous water availability. In both the aquatic and terrestrial habitats, no significant directional selection gradient was found for the stem diameter, the cortex area-to-stem area ratio or the density of vascular bundles. These results indicated that the anatomical structure of the A. philoxeroides stem may play an important role in the adaptation to changes in water availability.     

Effects of temperature and drought manipulations on seedlings of Scots pine provenances

Rising temperatures and more frequent and severe climatic extremes as a consequence of climate change are expected to affect growth and distribution of tree species that are adapted to current local conditions. Species distribution models predict a considerable loss of habitats for Pinus sylvestris. These models do not consider possible intraspecific differences in response to drought and warming that could buffer those impacts. We tested 10 European provenances of P. sylvestris, from the southwestern to the central European part of the species distribution, for their response to warming and to drought using a factorial design. In this common‐garden experiment the air surrounding plants was heated directly to prevent excessive soil heating, and drought manipulation, using a rain‐out shelter, permitted almost natural radiation, including high light stress. Plant responses were assessed as changes in phenology, growth increment and biomass allocation. Seedlings of P. sylvestris revealed a plastic response to drought by increased taproot length and root–shoot ratios. Strongest phenotypic plasticity of root growth was found for southwestern provenances, indicating a specific drought adaptation at the cost of overall low growth of aboveground structures even under non‐drought conditions. Warming had a minor effect on growth but advanced phenological development and had a contrasting effect on bud biomass and diameter increment, depending on water availability. The intraspecific variation of P. sylvestris provenances could buffer climate change impacts, although additional factors such as the adaptation to other climatic extremes have to be considered before assisted migration could become a management option.     

Influence of light,dark, temperature and drought on metabolite and ion composition in nectar and nectaries of an epiphytic bromeliad species (Aechmea fasciata)

• Research into the influence of stress factors, such as drought, different temperatures and/or varied light conditions, on plants due to climate changes is becoming increasingly important. Epiphytes, like many species of the Bromeliaceae, are particularly affected by this, but little is known about impacts on nectar composition and nectary metabolism.
• We investigated the influence of drought, different temperatures and light–dark regimes on nectar and nectaries of the epiphytic bromeliad species, Aechmea fasciata, and also the influence of drought with the terrestrial bromeliad, Billbergia nutans. The content of sugars, amino acids and ions in nectar and nectaries was analysed using HPLC. In addition, the starch content and the activities of different invertases in nectaries were determined.
• Compositions of nectar and nectaries were hardly influenced, neither by light nor dark, nor by different temperatures. In contrast, drought revealed changes in nectar volumes and nectar sugar compositions in the epiphytic bromeliad as well as in the terrestrial bromeliad. In both species, the sucrose‐to‐hexose ratio in nectar decreased considerably during the drought period. These changes in nectar sugar composition do not correlate with changes in the nectaries. The total sugar, amino acid and ion concentrations remained constant in nectar as well as in nectaries during the drought period.
• Changes in nectar composition or in the production of floral pollinator rewards are likely to affect plant–pollinator interactions. It remains questionable how far the adaptations of the bromeliads to drought and diverse light or temperature conditions are still sufficient.

     

Crassulacean Acid Metabolism and Crassulacean Acid Metabolism Modifications in Peperomia camptotricha

Peperomia camptotricha, a tropical epiphyte from Mexico, shows variable forms of Crassulacean acid metabolism (CAM). Young leaves exhibit CAM-cycling, while mature leaves show an intermediate type of metabolism, between CAM and CAM-cycling, having approximately the same amount of nighttime gas exchange as daytime. Metabolism of young leaves appears independent of daylength, but mature leaves have a tendency toward more CAM-like metabolism under short days (8 hours). Large differences in the physical appearance of plants were found between those grown under short daylengths and those grown under long daylengths (14 hours). Some anatomical differences were also detected in the leaves. Water stress caused a switch to CAM in young and mature leaves, and as water stress increased, they shifted to CAM-idling.     

Clonal integration facilitates spread of Paspalum paspaloides from terrestrial to cadmium‐contaminated aquatic habitats

• Cadmium (Cd) is a hazardous environmental pollutant with high toxicity to plants, which has been detected in many wetlands. Clonal integration (resource translocation) between connected ramets of clonal plants can increase their tolerance to stress. We hypothesised that clonal integration facilitates spread of amphibious clonal plants from terrestrial to Cd‐contaminated aquatic habitats.
• The spread of an amphibious grass Paspalum paspaloides was simulated by growing basal older ramets in uncontaminated soil connected (allowing integration) or not connected (preventing integration) to apical younger ramets of the same fragments in Cd‐contaminated water.
• Cd contamination of apical ramets of P. paspaloides markedly decreased growth and photosynthetic capacity of the apical ramets without connection to the basal ramets, but did not decrease these properties with connection. Cd contamination did not affect growth of the basal ramets without connection to the apical ramets, but Cd contamination of 4 and 12 mg·l^?1 significantly increased growth with connection. Consequently, clonal integration increased growth of the apical ramets, basal ramets and whole clones when the apical ramets were grown in Cd‐contaminated water of 4 and 12 mg·l^?1. Cd was detected in the basal ramets with connection to the apical ramets, suggesting Cd could be translocated due to clonal integration. Clonal integration, most likely through translocation of photosynthates, can support P. paspaloides to spread from terrestrial to Cd‐contaminated aquatic habitats.
• Amphibious clonal plants with a high ability for clonal integration are particularly useful for re‐vegetation of degraded aquatic habitats caused by Cd contamination.

     

Plant water deficits and insect responses: the preference of Corythucha arcuata (Heteroptera: Tingidae) for the foliage of white oak, Quercus alba

ABSTRACT.

• 1 The preference of Corythucha arcuata (Say) (Heteroptera: Tingidae) for the foliage of Quercus alba L. (Fagaceae) grown under water deficit was examined. Potted Q.alba saplings were grown under controlled levels of water deficit in a glasshouse. Adult C.arcuata were exposed to excised Q.alba foliage under controlled conditions in a growth chamber, and feeding preference assessed by recording the percentage of individuals feeding on leaves from each level of water deficit.
• 2 Two experiments were performed. In the first, all foliage was supplemented with water (via the petiole) to alleviate physical changes in the leaves that accompany plant water deficits. In the second experiment, leaves were not supplemented with water.
• 3 C.arcuata had no preference when presented water supplemented leaves, but preferred leaves that were fully hydrated when presented leaves that were not supplemented with water.
• 4 These results suggest that plant water deficits are important in determining the feeding preference of C.arcuata because they lead to avoidance of drought grown foliage. This avoidance may be caused by an increase in the metabolic cost to the herbivore of maintaining water balance when ingesting drought grown foliage or to an increase in foliage toughness.

     

<Emphasis Type="Italic">Arabidopsis</Emphasis>plants grown in the field and climate chambers significantly differ in leaf morphology and photosystem components

Background  

Plants exhibit phenotypic plasticity and respond to differences in environmental conditions by acclimation. We have systematically compared leaves of Arabidopsis thaliana plants grown in the field and under controlled low, normal and high light conditions in the laboratory to determine their most prominent phenotypic differences.     

Physio‐biochemical assessment and expression analysis of genes associated with drought tolerance in sugarcane (Saccharum spp. hybrids) exposed to GA3 at grand growth stage

• Drought is one of the most serious environmental factors limiting production of sugarcane worldwide. In order to assess the influence of gibberellins (GA₃) on drought and plant growth, along with associated physio‐biochemical attributes, expression of eight drought‐responsive genes were quantified and analysed.
• At grand growth stage (120 DAP) two sugarcane varieties (CoLk94184, CoPK05191) were exposed to drought by withholding irrigation. GA₃ (35 ppm) was applied using battery‐operated uniform controlled dispensing sprayer twice at 1‐week intervals on 2‐week drought‐stressed plants. Physio‐biochemical attributes including antioxidant enzyme activities were estimated following standard protocols. RT‐PCR was performed to visualise the drought‐associated gene expression patterns.
• Drought triggered a reduction in RWC and chlorophyll content but these recovered when droughted plants were exposed to GA₃. Proline content increased many fold in both varieties under stress, but decreased under the influence of GA₃. There was a mixed response of antioxidant enzyme activity, which distinctly declined after GA₃ exposure, together with a lesser reduction in dry matter content over that of control plants. With increasing stress, expression of pyrroline‐5‐carboxylase synthetase (P5CS) and betaine‐aldehyde dehydrogenase genes was observed, selectively up‐regulated in CoPK05191. Expression of proline oxidase/transporter was high in CoPK05191 but diminished along with proline content after exposure to GA_3. CoLk94184 showed no significant difference in P5CS gene expression under stress condition, whereas expression of betaine‐aldehyde dehydrogenase gene was unchanged in response to stress.
• Results demonstrated that exposure of droughted plants to GA₃ not only led to recovery of activity of drought‐associated physio‐biochemical attributes, but also minimised impact on cane dry weight and quality. Further, GA₃ application caused differential gene expression that possibly triggers increased responsiveness towards drought tolerance in sugarcane.