Growth and Respiration in Plants from Various Adaptation Groups as Affected by Mineral Nutrient Deficiency

The effect of the deficiency in mineral nutrients was investigated in plant species representing various adaptation groups (stress-tolerant, competitive, and ruderal plants). Dry and fresh weight, as well as the length of shoots and underground organs, were determined in 20- to 50-day-old seedlings. The ratio between the dry weights of shoot and root (SRR), relative growth rate (RGR), the rate of total dark respiration (R), gross photosynthesis (P _g), and the proportion of the respiratory expenditures to gross photosynthesis (R/P _g) were calculated. When affected by a deficiency in mineral nutrients, the weight of the whole plant decreased. In resistant species of clover (Trifolium pratense L.) and alfalfa (Medicago sativa L.), this reduction was insignificant, whereas, in the ruderal species amaranth (Amaranthus retroflexus L.), it was at its highest. In all the species investigated, the ratio R/P _g was 38–46%. Under stress conditions, this index increased. Given a deficiency in mineral nutrients, the changes in SRR, RGR, and R/P _g were greater in amaranth, suggesting that this plant species is less tolerant to stress. The correlation between RGR and R observed in amaranth under normal conditions indicates that the major energy expenditures are associated with growth. Under stress conditions, such a correlation was not observed. In more resistant species of clover and alfalfa, a weak positive correlation between RGR and R was observed both under normal and stress conditions. In these species, the deficiency in mineral nutrients probably brought about a reduction in the growth component of total dark respiration and a rise in the adaptation component. The complex of indices (R/P _g, RGR, and SRR) and the extent of their variation in the seedlings describe the potential productivity and resistance of particular species to a deficiency in mineral nutrients and may characterize the adaptation type of the plants.     

葡萄幼苗在温度胁迫交叉适应过程中对水杨酸的应答

在温度锻炼诱导葡萄幼苗对交叉温度逆境的适应过程中叶片内源SA变化的结果表明,0℃低温胁迫期间,葡萄幼苗叶片细胞膜系统受到严重伤害,丙二醛(MDA)含量明显升高;此时自由态SA含量呈波动性变化,并随着胁迫进程的延长,内源SA含量明显低于正常叶片水平。而经过高温锻炼的幼苗,在低温胁迫初期自由态SA含量迅速达到一个高峰,之后回落并保持在正常叶片的SA水平,MDA含量也相应降低且相对稳定。结合态SA的变化相对较平稳,并且总SA含量变化趋势与自由态SA含量的变化趋势相吻合。在45℃高温胁迫期间,经过低温锻炼的幼苗的上述各项指标的变化规律与经过高温锻炼的幼苗在低温胁迫期间的变化趋势相似。     

Photosensory Perception and Signal Transduction in Higher Plants — Molecular Genetic Analysis

Light plays a crucial role throughout the life cycle of higher plants modulating various aspects of their growth and development, such as seed germination, leaf differentiation, flowering, and senescence. Plants have thus evolved extremely sensitive mechanisms to continually detect the changing ambient light conditions and transduce the information to the gene expression machinery. The elucidation of this complex information sensing and transduction machinery is fundamental to our understanding of the molecular mechanisms involved in light-regulated plant development. The last decade has witnessed an immense upsurge in information in this regard and the mechanism of photosensory perception and phototransduction is turning out to be quite intricate, involving an array of cellular effectors and biochemical messengers. The analysis of photomorphogenic mutants, predominantly of Arabidopsis, has revealed interesting facts, not only about the intricacies of light signaling circuitry, but also about the multiplicity of the photoreceptors and their specialized or overlapping photosensory functions. In addition, these studies have also highlighted, and in some cases even redefined, the role of conventional plant growth regulators in modulating photomorphogenic development. Employing standard recombinant DNA techniques, substantial information has also become available about the regulatory cis-acting DNA sequences that make a gene amenable to light control and the trans-acting protein factors that can potentially interact with these cis-acting sequences on receiving the signal from the upstream transduction components. The information available to date on these emerging trends in photomorphogenesis research has been summarized and critically evaluated in this review.     

Persistent Firing and Adaptation in Optic-Flow-Sensitive Descending Neurons

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Basic Types of Structural Changes in the Leaf Mesophyll during Adaptation of Eastern Pamir Plants to Mountain Conditions

Quantitative characteristics of mesophyll structure were compared in leaves of eleven alpine plant species grown under natural conditions in the Eastern Pamirs at various altitudes, from 3800 to 4750 m. Basic types of changes in mesophyll structure, associated with plant adaptation to mountain conditions, were characterized. These changes manifested themselves in different numbers of cell layers and cell sizes in the palisade tissue and, as a consequence, in changed leaf thickness and cell number per unit of leaf area. Three plant groups were identified by the changes in the leaf structural characteristics depending on the type of mesophyll structure, ecological group of plant species, and altitude of plant habitat. The first group comprised alpine xerophytes with an isopalisade structure, in which the volume of palisade cells decreased and their number per unit of leaf area increased with the altitude of plant habitat. The number of mesophyll layers and leaf thickness decreased or did not change with altitude. The second group comprised subalpine plant species with a dorsoventral structure of mesophyll; these species occur below the line of continuous night frost. In these plant species, the number of mesophyll layers, leaf thickness, and cell number per unit of leaf area increased with altitude. The third group comprised mesophyte plants with a dorsoventral and homogenous mesophyll structure, which are encountered in a wide range of habitats, including the nival belt (from 4700 to 5000 m). In this group, cell volume increased and cell number per unit of leaf area decreased with altitude. We present a general scheme of leaf structural changes, which explains the changes in the quantitative characteristics of mesophyll as a function of altitude and highland environmental conditions.     

Adaptation to host plants may prevent rapid insect responses to climate change

We must consider the role of multitrophic interactions when examining species' responses to climate change. Many plant species, particularly trees, are limited in their ability to shift their geographic ranges quickly under climate change. Consequently, for herbivorous insects, geographic mosaics of host plant specialization could prohibit range shifts and adaptation when insects become separated from suitable host plants. In this study, we examined larval growth and survival of an oak specialist butterfly (Erynnis propertius) on different oaks (Quercus spp.) that occur across its range to determine if individuals can switch host plants if they move into new areas under climate change. Individuals from Oregon and northern California, USA that feed on Q. garryana and Q. kelloggii in the field experienced increased mortality on Q. agrifolia, a southern species with low nutrient content. In contrast, populations from southern California that normally feed on Q. agrifolia performed well on Q. agrifolia and Q. garryana and poorly on the northern, high elevation Q. kelloggii. Therefore, colonization of southern E. propertius in higher elevations and some northern locales may be prohibited under climate change but latitudinal shifts to Q. garryana may be possible. Where shifts are precluded due to maladaptation to hosts, populations may not accrue warm‐adapted genotypes. Our study suggests that, when interacting species experience asynchronous range shifts, historical local adaptation may preclude populations from colonizing new locales under climate change.     

植物对逆境交叉适应的分子机制

交叉适应(cross-adaptation)是植物应答复合逆境的主要表现形式,它涉及环境刺激、信号转导、基因表达及细胞代谢调节等.为明确交叉适应的分子机制,本文从活性氧、激素、促细胞分裂原激活性蛋白激酶等方面进行了综述,以深入系统地阐明植物对逆境的响应,为作物抗逆栽培提供经济、高效的途径.     

Interspecific and intraspecific diversity in oak powdery mildews in Europe: coevolution history and adaptation to their hosts

Quercus has been reported as the genus with the largest number of attacking powdery mildews. In Europe, oak powdery mildew was rarely reported before 1907, when severe outbreaks were observed. These epidemics were attributed to the newly described species Erysiphe alphitoides, presumed to be of exotic origin. After the burst of interest following the emergence of the disease, research on this topic remained very limited. Interest in research was recently reactivated in response to the availability of molecular tools. This review summarizes current knowledge on the diversity of oak powdery mildews in Europe and their possible evolutionary relationships with European oaks. The most striking results are the evidence of cryptic diversity (detection in France of a lineage closely related to Erysiphe quercicola, previously thought to only have an Asian distribution), large host range (similarity of E. alphitoides and E. quercicola with powdery mildews of tropical plants) but also local adaptation to Quercus robur. These recent findings highlight the complexity of the history of oak powdery mildew in Europe and point to the question of host specialization and host jumps in the evolution of powdery mildew fungi.     

Loading Mode Interactions in Simulations of Long Bone Cross-Sectional Adaptation

Although many bone adaptation theories have been formulated to address both trabecular and cortical adaptation, most applications have focused on trabecular adaptation. Thus far, no thorough investigations of the influence of different types of loading on predicted patterns of long bone cross-sectional adaptation have been reported. In the current study, we present a new model for long bone cross-sectional adaptation that incorporates axial, bending and torsional loading components. We found that bending moments have a strong potential to modulate cross-sectional geometry, but can produce unforseen (and unrealistic) geometric instabilities. Torsional moments have the ability to suppress these instabilities, suggesting that torsion may play a more significant role in guiding long bone development than previously recognized. Our results also call into question the concept of strict “remodeling equilibrium,” suggesting that long bones do not necessarily approach a state of uniform mechanical stimulation. This modeling approach provides an additional perspective on experimental studies, and may lead to a greater understanding of the interaction between mechanics and biology in long bone adaptation.     

The Role of Adaptation to Host Plants in the Evolution of Reproductive Isolation: Negative Evidence from Tetranychus Urticae Koch

Reproductive isolation between demes of a phytophagous arthropod population that use different host plant species could evolve in two different ways. First, adaptation to different host species might result in reproductive isolation as a pleiotropic by-product. Second, if adaptation to one host species strongly reduces fitness on others, selection could favour mechanisms, such as host fidelity and assortative mating, that restrict gene flow between host-adapted demes. A laboratory selection experiment on the broadly polyphagous spider mite Tetranychus urticae gave information on these possibilities. A population allowed to adapt to tomato plants showed increased survival, development rate and fecundity on tomato relative to the base population from which it was derived. In spite of the large difference between the tomato-adapted and base populations in performance on tomato plants, the two populations showed no evidence of reproductive isolation, as measured by the hatching rate of eggs laid by F1 hybrids between the lines. Furthermore, a genetically variable population formed by hybridizing the tomato-adapted and base populations did not show evidence for a decline in ability to survive on tomato after more than ten generations of mass rearing on lima bean, indicating that tomato-adapted genotypes suffered little or no selective disadvantage on bean. These results give no support for the role of host plants in the evolution of reproductive isolation in T. urticae.     

Experimental studies of adaptation in Clarkia xantiana. II. Fitness variation across a subspecies border

Because the range boundary is the locale beyond which a taxon fails to persist, it provides a unique opportunity for studying the limits on adaptive evolution. Adaptive constraints on range expansion are perplexing in view of widespread ecotypic differentiation by habitat and region within a species' range (regional adaptation) and rapid evolutionary response to novel environments. In this study of two parapatric subspecies, Clarkia xantiana ssp. xantiana and C. x. ssp. parviflora, we compared the fitness of population transplants within their native region, in a non-native region within the native range, and in the non-native range to assess whether range expansion might be limited by a greater intensity of selection on colonists of a new range versus a new region within the range. The combined range of the two subspecies spans a west-to-east gradient of declining precipitation in the Sierra Nevada of California, with ssp. xantiana in the west being replaced by ssp. parviflora in the east. Both subspecies had significantly higher fitness in the native range (range adaptation), whereas regional adaptation was weak and was found only in the predominantly outcrossing ssp. xantiana but was absent in the inbreeding ssp. parvifilora. Because selection intensity on transplants was much stronger in the non-native range relative to non-native regions, there is a larger adaptive barrier to range versus regional expansion. Three of five sequential fitness components accounted for regional and range adaptation, but only one of them, survivorship from germination to flowering, contributed to both. Flower number contributed to regional adaptation in ssp. xantiana and fruit set (number of fruits per flower) to range adaptation. Differential survivorship of the two taxa or regional populations of ssp. xantiana in non-native environments was attributable, in part, to biotic interactions, including competition, herbivory, and pollination. For example, low fruit set in ssp. xantiana in the east was likely due to the absence of its principal specialist bee pollinators in ssp. parviflora's range. Thus, convergence on self-fertilization may be necessary for ssp. xantiana to invade ssp. parviflora's range, but the evolution of outcrossing would not be required for ssp. parviflora to invade ssp. xantiana's range.     

Novelty and Convergence in Adaptation to Whole Genome Duplication

Whole genome duplication (WGD) can promote adaptation but is disruptive to conserved processes, especially meiosis. Studies in Arabidopsis arenosa revealed a coordinated evolutionary response to WGD involving interacting proteins controlling meiotic crossovers, which are minimized in an autotetraploid (within-species polyploid) to avoid missegregation. Here, we test whether this surprising flexibility of a conserved essential process, meiosis, is recapitulated in an independent WGD system, Cardamine amara, 17 My diverged from A. arenosa. We assess meiotic stability and perform population-based scans for positive selection, contrasting the genomic response to WGD in C. amara with that of A. arenosa. We found in C. amara the strongest selection signals at genes with predicted functions thought important to adaptation to WGD: meiosis, chromosome remodeling, cell cycle, and ion transport. However, genomic responses to WGD in the two species differ: minimal ortholog-level convergence emerged, with none of the meiosis genes found in A. arenosa exhibiting strong signal in C. amara. This is consistent with our observations of lower meiotic stability and occasional clonal spreading in diploid C. amara, suggesting that nascent C. amara autotetraploid lineages were preadapted by their diploid lifestyle to survive while enduring reduced meiotic fidelity. However, in contrast to a lack of ortholog convergence, we see process-level and network convergence in DNA management, chromosome organization, stress signaling, and ion homeostasis processes. This gives the first insight into the salient adaptations required to meet the challenges of a WGD state and shows that autopolyploids can utilize multiple evolutionary trajectories to adapt to WGD.     

Adaptation to sulfide and to the underwater light field in three cyanobacterial isolates from Lake Arcas (Spain)

Abstract: Three strains of cyanobacteria isolated from karstic Lake Arcas were tested for photosynthetic adaptations to soluble sulfide. One of them, AO11, was identified as Oscillatoria cf. ornata , and forms dense populations in the sulfide-rich anoxic hypolimnion of this lake. This cyanobacterium was able to perform sulfide-dependent anoxygenic photosynthesis and its oxygenic photosynthesis was relatively insensitive to sulfide. The other strains studied were AP1 and AO21, identified respectively as Pseudanabaena sp. and Oscillatoria cf. tenuis , populations of which were present only in epilimnetic waters at low population densities. Pseudanabaena sp. also carried out anoxygenic photosynthesis, but oxygenic photosynthesis was totally inhibited by 0.5 mM sulfide. Oscillatoria cf. tenuis lost most of its oxygenic photosynthetic capacity when submitted to 0.1 mM sulfide and anoxygenic photosynthesis accounted for less than 20% of sulfide-free controls. In addition to different photosynthetic capabilities, the three cyanobacteria exhibited differences in light-harvesting photosynthetic accessory pigments. Pigment analysis of cultures grown under different light conditions showed the capacity of Oscillatoria cf. ornata AO11 to produce phycoerythrin under low light intensity or under predominantly green light, while neither Pseudanabaena sp. AP1 nor Oscillatoria cf. tenuis AO21 produced this pigment. The complementary chromatic adaptation of Oscillatoria cf. ornata correlates well with its summertime distribution under the dim light field of the hypolimnion. The distribution and abundance of specific cyanobacterial populations in Lake Arcas can thus be explained by the interplay of light regime and presence of sulfide as some of the most determinant ecological parameters.     

Independent Molecular Basis of Convergent Highland Adaptation in Maize

Convergent evolution is the independent evolution of similar traits in different species or lineages of the same species; this often is a result of adaptation to similar environments, a process referred to as convergent adaptation. We investigate here the molecular basis of convergent adaptation in maize to highland climates in Mesoamerica and South America, using genome-wide SNP data. Taking advantage of archaeological data on the arrival of maize to the highlands, we infer demographic models for both populations, identifying evidence of a strong bottleneck and rapid expansion in South America. We use these models to then identify loci showing an excess of differentiation as a means of identifying putative targets of natural selection and compare our results to expectations from recently developed theory on convergent adaptation. Consistent with predictions across a wide parameter space, we see limited evidence for convergent evolution at the nucleotide level in spite of strong similarities in overall phenotypes. Instead, we show that selection appears to have predominantly acted on standing genetic variation and that introgression from wild teosinte populations appears to have played a role in highland adaptation in Mexican maize.     

细胞培养技术在植物抗性生理研究领域中的应用

本文综述了近10年来有关利用细胞培养技术所进行的抗性生理领域的研究成果,包括在培养过程中植物细胞对外界胁迫的反应、有关利用细胞培养技术研究植物的抗逆性反应,以及植物抗逆性的理论在实际中的应用。大量的实验证明,细胞培养技术在植物抗逆性研究领域具有广阔的应用前景。     

荒漠植物种子粘液的生态学意义

种子粘液是在种皮外层细胞的高尔基体内产生并分泌到胞腔内或细胞壁层的吸湿膨胀的一类果胶类多糖物质。具粘液种子的植物大多生长在荒漠地区,广泛存在于十字花科、菊科和车前科等类群中。粘液的存在对荒漠植物种子的扩散、萌发、防御以及幼苗的生长等都具有重要的生态学意义,是荒漠植物适应干旱少雨的生态环境的有效对策之一。对粘液种子的研究不仅可全面揭示荒漠植物的生态适应机制及其进化生态意义,还可为研究基因控制的糖类生物合成和分泌、细胞次生壁的生物合成及形态分化建立理想的模式体系。为此,在广泛查阅相关文献的基础上,该文综合分析了国内外种子粘液的研究进展,并重点探讨了以下几方面问题：（1）种子粘液的化学成分：（2）粘液及粘液种皮的形态特征：（3）粘液细胞分化与粘液生物合成的细胞学及基因调控机制以及粘液的释放方式：（4）种子粘液的生态学意义。在此基础上展望了今后的研究方向,以期为推动我国荒漠植物种子生态学的理论与应用研究及西部荒漠区的植物物种多样性保护和生态保育提供重要理论依据。     

A framework to gauge the epidemic potential of plant pathogens in environmental reservoirs: the example of kiwifruit canker

New economically important diseases on crops and forest trees emerge recurrently. An understanding of where new pathogenic lines come from and how they evolve is fundamental for the deployment of accurate surveillance methods. We used kiwifruit bacterial canker as a model to assess the importance of potential reservoirs of new pathogenic lineages. The current kiwifruit canker epidemic is at least the fourth outbreak of the disease on kiwifruit caused by Pseudomonas syringae in the mere 50 years in which this crop has been cultivated worldwide, with each outbreak being caused by different genetic lines of the bacterium. Here, we ask whether strains in natural (non‐agricultural) environments could cause future epidemics of canker on kiwifruit. To answer this question, we evaluated the pathogenicity, endophytic colonization capacity and competitiveness on kiwifruit of P. syringae strains genetically similar to epidemic strains and originally isolated from aquatic and subalpine habitats. All environmental strains possessing an operon involved in the degradation of aromatic compounds via the catechol pathway grew endophytically and caused symptoms in kiwifruit vascular tissue. Environmental and epidemic strains showed a wide host range, revealing their potential as future pathogens of a variety of hosts. Environmental strains co‐existed endophytically with CFBP 7286, an epidemic strain, and shared about 20 virulence genes, but were missing six virulence genes found in all epidemic strains. By identifying the specific gene content in genetic backgrounds similar to known epidemic strains, we developed criteria to assess the epidemic potential and to survey for such strains as a means of forecasting and managing disease emergence.     

Adaptation of redband trout in desert and montane environments

Natural populations that evolve under extreme climates are likely to diverge because of selection in local environments. To explore whether local adaptation has occurred in redband trout (Oncorhynchus mykiss gairdneri) occupying differing climate regimes, we used a limited genome scan approach to test for candidate markers under selection in populations occurring in desert and montane streams. An environmental approach to identifying outlier loci, spatial analysis method and linear regression of minor allele frequency with environmental variables revealed six candidate markers (P < 0.01). Putatively neutral markers identified high genetic differentiation among desert populations relative to montane sites, likely due to intermittent flows in desert streams. Additionally, populations exhibited a highly significant pattern of isolation by temperature (P< 0.0001) and those adapted to the same environment had similar allele frequencies across candidate markers, indicating selection for differing climates. These results imply that many genes are involved in the adaptation of redband trout to differing environments, and selection acts to reinforce localization. The potential to predict genetic adaptability of individuals and populations to changing environmental conditions may have profound implications for species that face extensive anthropogenic disturbances.     

Adaptation and habitat selection in the eco-evolutionary process

The struggle for existence occurs through the vital rates of population growth. This basic fact demonstrates the tight connection between ecology and evolution that defines the emerging field of eco-evolutionary dynamics. An effective synthesis of the interdependencies between ecology and evolution is grounded in six principles. The mechanics of evolution specifies the origin and rules governing traits and evolutionary strategies. Traits and evolutionary strategies achieve their selective value through their functional relationships with fitness. Function depends on the underlying structure of variation and the temporal, spatial and organizational scales of evolution. An understanding of how changes in traits and strategies occur requires conjoining ecological and evolutionary dynamics. Adaptation merges these five pillars to achieve a comprehensive understanding of ecological and evolutionary change. I demonstrate the value of this world-view with reference to the theory and practice of habitat selection. The theory allows us to assess evolutionarily stable strategies and states of habitat selection, and to draw the adaptive landscapes for habitat-selecting species. The landscapes can then be used to forecast future evolution under a variety of climate change and other scenarios.