Heterogeneous Light Environment Research Articles

Red and Blue Light Induce Soybean Resistance to Soybean Mosaic Virus Infection through the Coordination of Salicylic Acid and Jasmonic Acid Defense Pathways.

Soybean mosaic virus (SMV) seriously harms soybean quality and yield. In order to understand the effect of a heterogeneous light environment on the disease resistance of intercropped soybeans, we simulated three kinds of light environments to learn the effects of white light, blue light, and far-red light on the SMV resistance of soybeans. The results showed that compared with the control, SMV-infected soybeans showed dwarfing and enhanced defense. The symptoms of leaves under red and blue light were less severe than those under white light, the virus content of infected plants was about 90% lower than under white light, the activity of antioxidant enzymes increased, and the accumulation of reactive oxygen species decreased. The oxidation damage in SMV-infected soybeans was serious under far-red light. Transcriptome data showed that the biostimulatory response, plant-pathogen interaction, and plant hormone signaling pathway gene expression of SMV-infected soybeans were significantly up-regulated under red light compared with the control. Compared with the control, the genes in the biostimulatory response, calcium ion binding, carbohydrate-binding, mitogen-activated protein kinase (MAPK) signaling, and plant-pathogen interaction pathways, were significantly up-regulated in SMV-infected soybeans under blue light. In far-red light, only 39 genes were differentially expressed in SMV-infected soybeans compared with the control, and most of the genes were down-regulated. Compared with the control, the up-regulation of the salicylic acid (SA) pathway defense gene in SMV-infected soybeans under red light was higher than under other light treatments. Compared with the control, the up-regulation of the jasmonic acid (JA) and ethylene (ET) pathway defense genes in SMV-infected soybeans under blue light was higher than under other light treatments. Compared with the control, most defense-related genes in the SA and JA pathways were inhibited in SMV-infected soybeans under far-red light, while genes in the ET pathway were significantly up-regulated. These results will advance our understanding of the disease resistance mechanism of intercropping soybeans in a heterogeneous light environment and provide new ideas for the prevention and control of viral diseases.

Developmental and environmental plasticity in opsin gene expression in Lake Victoria cichlid fish.

In many organisms, sensory abilities develop and evolve according to the changing demands of navigating, foraging, and communication across different environments and life stages. Teleost fish inhabit heterogeneous light environments and exhibit a large diversity in visual system properties among species. Cichlids are a classic example of this diversity; visual system variation is generated by different tuning mechanisms that involve both genetic factors and phenotypic plasticity. Here, we document the developmental progression of visual pigment gene expression in Lake Victoria cichlids and test if these patterns are influenced by variation in light conditions. We reared two sister species of Pundamilia to adulthood in two distinct visual conditions that resemble the light environments that they naturally inhabit in Lake Victoria. We also included interspecific first-generation hybrids. We focused on the four opsins that are expressed in Pundamilia adults (using real-time quantitative polymerase chain reaction (RT-qPCR)) (SWS2B, SWS2A, RH2A, and LWS) at 17 time points. We find that opsin expression profiles progress from shorter-wavelength sensitive opsins to longer-wavelength sensitive opsins with increasing age, in both species and their hybrids. The developmental trajectories of opsin expression also responded plastically to the visual conditions. Developmental and environmental plasticity in opsin expression may provide an important stepping stone in the evolution of cichlid visual system diversity.

Periploca sepium leaf dry weight, area, and thickness scale differently under different light environments in Taohe riparian forests

Understanding the variation in plant morphological characteristics under heterogeneous light environments is important to comprehend the adaptation strategies of riparian forest plants. Among the plant parts, leaves are the most sensitive to changes in the environment, and their functional traits and correlations among them can reflect the pathways and mechanisms of a plant's response to environmental changes. The allometric relationship between leaf dry weight (LDW), leaf area (LA) and leaf thickness (LT) in Periploca sepium under three natural habitat conditions, namely, under canopy, gap, and full sun areas in the Taohe riparian forest, was examined by using the standardized major axis (SMA) estimation method and correlation analysis. In the under canopy area, LDW and LA showed an allometric growth relationship (SMA slope < 1), whereas LDW and LT displayed an isometric relationship (SMA slope = 1). In the gap area, LDW was isometrically related to the LA and LT (SMA slope = 1). In the full sun area, LDW and LT showed an allometric relationship (SMA slope > 1), whereas LDW and LA showed an isometric relationship (SMA slope = 1). LA, LT, and LDW decreased by 34.3%, 45.0%, and 40.4%, respectively, in plants from the under canopy area to the full light area. Moreover, the transpiration rate (Tr), net photosynthetic rate (Pn), stomatal conductance (Gs), and vapour pressure deficit (VPD) of Periploca sepium increased 1.29-fold, 13.5%, 63.2%, and 29.7%, respectively, from the under canopy area to the full sun area. Periploca sepium developed large, thick leaves in the under canopy area, and small, thin leaves in the full sun area, demonstrating the investment trade-off mechanism of plant leaf functional traits to adapt to the heterogeneous light environment.

Long-time behavior of swimming Euglena gracilis in a heterogenous light environment.

The cell motion of Euglena gracilis in homogeneous and heterogeneous light environments was analyzed. Homogeneous and heterogeneous environments were prepared, with only a red color or with a red circle surrounded by brighter white regions, respectively. In a heterogeneous environment, the cells move into the red circle. Swimming orbits at 1/25s intervals for 120s were analyzed. The speed distribution of the 1 s-averaged cell orbits in a homogeneous environment was different from that in a heterogeneous environment, where the faster swimming fraction was enhanced. The relationship between speed and curvature radius was analyzed using a joint histogram. Histograms for short timescale motion, constructed by 1 s-averaged orbits, suggest that the cell swimming curves are not biased, while those for long timescale motion, constructed by 10 s-averaged orbits, suggest that the cell swimming curves are biased in the clockwise direction. Furthermore, the curvature radius determines the speed, which does not seem to depend on the light environment. The mean squared displacement in a heterogeneous environment is larger than that in a homogeneous environment on a 1s timescale. These results will be the basis for constructing a model for the long-time behavior of photomovement for light differences.

Seed germination of

Context Some plant species show within-generational and trans-generational phenotypic plasticity associated with the light environment for germination traits. In bromeliads, light affects the seed germination of several species, but there is no study analysing the effects of the light environment where the mother plant lived on seed germination. Bromelia serra inhabits the understorey of xerophytic forests, where individuals could be conditioned by the heterogeneous light environment because its cover and abundance are negatively associated with tree basal area and woody vegetation cover. Aims To analyse the effect of the light environment on seed germination of B. serra, considering also the light environment where the mother plant lived. Methods In four patches from three different sites in a stand of a Schinopsis balansae forest, 48 fruiting plants of B. serra were harvested. Canopy openness was obtained from a hemispherical photograph taken above each plant. From each infructescence, half of the seeds from five fruit were kept in light conditions and the remaining seeds in dark conditions in a germination room. Key results There was no effect of the light environment where mother plants lived on seed germination, but the light environment in the germination room positively affected germination variables. Conclusions The positive effect of light on seed germination of B. serra might explain the spatial distribution of individual plants in these xerophytic forests. Implications These results have enhanced our understanding of the regeneration and distribution of understorey herbaceous species in these South American forests.

Relationship between Canopy Structure and Community Structure of the Understory Trees in a Beech Forest in Japan

Understory trees occupy a spatially heterogeneous light environment owing to light interception by patchily distributed canopy leaves. We examined the spatial distribution of canopy leaves and the spatial structure of the understory tree community (height &lt; 5 m) and their relationships in a beech forest in Nagano, Japan. We measured the canopy leaf area index (LAI) at 10 m intervals (n = 81) in a permanent research plot (1 ha). We established a circular subplot centered on each LAI measurement point, and determined the species composition and the aboveground net primary production of wood (ANPPW) of the understory tree community by using tree size data from an open database in the Monitoring Sites 1000 project. There was a significant negative correlation between canopy LAI and the ANPPW of understory trees and a significant positive correlation between the ANPPW of understory and understory tree density. The dominant species of understory trees differed between subplots with high and low LAI values. Our results suggest that niche differentiation allows trees in the understory community to make use of various light conditions, thereby enhancing the primary productivity of the entire community.

Systemic regulation of photosynthetic function in maize plants at graining stage under a vertically heterogeneous light environment

To cope with a highly heterogeneous light environment, photosynthesis in plants can be regulated systemically. Currently, the majority of studies are carried out with various plants during the vegetative growth period. As the reproductive sink improves photosynthesis, we wondered how photosynthesis is systemically regulated at the reproductive stage under a vertically heterogeneous light environment in the field. Therefore, changes of light intensity within canopy, chlorophyll content, gas exchange, and chlorophyll a fluorescence transient were carefully investigated at the graining stage of maize under various planting densities. In this study, a high planting density of maize drastically reduced the light intensities in the lower canopy, and increased the difference in vertical light distribution within the canopy. With the increase of vertical heterogeneity, chlorophyll content, light-saturated photosynthetic rate and the quantum yield of electron transport in the ear leaf (EL) and the fourth leaf below the ear (FLBE) were decreased gradually, and the ranges of declines in these parameters were larger at FLBE than those at EL. Leaves in the lower canopy were shaded artificially to further test these results. Partial shading (PS) resulted in a vertically heterogeneous light environment and enhanced the differences in photosynthetic characteristics between EL and FLBE. Removing the tassel and top leaves (RTL) not only improved the vertical light distribution within the canopy, but also reduced the differences in photosynthetic characteristics between the two leaves. Taken together, these results demonstrated that maize plants could enhance the vertical heterogeneity of their photosynthetic function to adapt to their light environment; slight changes of the photosynthetic function in EL at the graining stage under a vertically heterogeneous light environment indicated that the systemic regulation of photosynthesis is weak at the graining stage.

Parental UV-B radiation regulates the habitat selection of clonal Duchesnea indica in heterogeneous light environments.

Habitat selection behaviour is an effective strategy adopted by clonal plants in heterogeneous understorey light environments, and it is likely regulated by the parental environment's ultraviolet-B radiation levels (UV-B) due to the photomorphogenesis of UV-B and maternal effects. Here, parental ramets of Duchesnea indica were treated with two UV-B radiation levels [high (UV5 group) and low (UV10 group)], newborn offspring were grown under a heterogeneous light environment (ambient light vs shade habitat), and the growth and DNA methylation variations of parents and offspring were analysed. The results showed that parental UV-B affected not only the growth of the parent but also the offspring. The offspring of different UV-B-radiated parents showed different performances. Although these offspring all displayed a tendency to escape from light environments, such as entering shade habitats earlier, and allocating more biomass under shade (33.06% of control, 42.28% of UV5 and 72.73% of UV10), these were particularly obvious in offspring of the high UV-B parent. Improvements in epigenetic diversity (4.77 of control vs 4.83 of UV10) and total DNA methylation levels (25.94% of control vs 27.15% of UV10) and the inhibition of shade avoidance syndrome (denser growth with shorter stolons and internodes) were only observed in offspring of high UV-B parents. This difference was related to the eustress and stress effects of low and high UV-B, respectively. Overall, the behaviour of D. indica under heterogeneous light conditions was regulated by the parental UV-B exposure. Moreover, certain performance improvements helped offspring pre-regulate growth to cope with future environments and were probably associated with the effects of maternal DNA methylation variations in UV-B-radiated parents.

Effects of ramet ratio on photosynthetic physiology of &lt;i&gt;Indocalamus decorus&lt;/i&gt; clonal system under heterogeneous light environment

Effects of ramet ratio on photosynthetic physiology of &lt;i&gt;Indocalamus decorus&lt;/i&gt; clonal system under heterogeneous light environment

Clonal integration and phosphorus management under light heterogeneity facilitate the growth and diversity of understory vegetation and soil fungal communities

The spatial heterogeneity of light and nutrient deficiency occurs in many forest understories. Proper fertilization management of unhealthy forests can benefit forest understory diversity and improve the stability of degraded soil; and clonal integration is a major advantage of resource sharing for many forest understory vegetation, such as pteridophytes. In this study, we tested whether understory soil fertilization and clonal integration under light heterogeneity were able to increase the performance and diversity of understory vegetation and soil microbial communities in nature. Field experiments—with or without phosphorus (P) addition, with intact or severed rhizome, and under homogeneous or heterogeneous light environments—were conducted in the understory of a typical evergreen forest in southeast China.Light heterogeneity, P addition and clonal integration promoted the growth, diversity and evenness of ferns and soil microbial biomass C, N and P (MBC, MBN and MBP) at both experimental plot and patch level. They also increased Chao1 richness and Shannon diversity of soil fungal communities at patch level, especially in the high light patches with P addition. The positive effects of P addition and clonal integration on the growth and diversity of ferns and soil microbial biomass were greatly increased under heterogeneous light. The positive effects of clonal integration on the growth were the greatest in the heterogeneous high light patches. Moreover, the interactive effect of P addition and clonal integration increased soil MBN and MBP. Clonal integration promoted the increased growth and diversity of ferns and soil MBC in the heterogeneous light environment (9.35%–35.19%), and enhanced soil MBN and MBP in the P addition treatment (9.03%–12.96%). The interactive effect of P addition and clonal integration largely led to the transition of fungal groups from slow-growing oligotrophic types to fast-growing copiotrophic types.Our results show that the interactions between clonal integration and/or P addition under light heterogeneity increase the benefits of ferns in light-rich patches, and further promote integrative performance of ferns and soil microbial communities.

Local weak light induces the improvement of photosynthesis in adjacent illuminated leaves in maize seedlings.

To copy with highly heterogeneous light environment, plants can regulate photosynthesis locally and systemically, thus, maximizing the photosynthesis of individual plants. Therefore, we speculated that local weak light may induce the improvement of photosynthesis in adjacent illuminated leaves in plants. In order to test this hypothesis, maize seedlings were partially shaded, and gas exchange, chlorophyll a fluorescence and biochemical analysis were carefully assessed. It was shown that local shading exacerbated the declines in the photosynthetic rates, chlorophyll contents, electron transport and carbon assimilation-related enzyme activities in shaded leaves as plants growth progressed. While, the decreases of these parameters in adjacent illuminated leaves of shaded plants were considerably alleviated compared to the corresponding leaves of control plants. Obviously, the photosynthesis in adjacent illuminated leaves in shaded plants was improved by local shading, and the improvement in adjacent lower leaves was larger than that in adjacent upper ones. As growth progressed, local shading induced higher abscisic acid contents in shaded leaves, but it alleviated the increase in the abscisic acid contents in adjacent leaves in shaded plants. Moreover, the difference in sugar content between shaded leaves and adjacent illuminated ones was gradually increased. Consequently, local weak light suppressed the photosynthesis in shaded leaves, while it markedly improved the photosynthesis of adjacent illuminated ones. Sugar gradient between shaded leaves and adjacent illuminated ones might play a key role in photosynthetic regulation of adjacent illuminated leaves.

Spatial genet dynamics of a dwarf bamboo: Clonal expansion into shaded forest understory contributes to regeneration after an episodic die‐off

AbstractThe ability of clonal plants to spread horizontally and to share resources within genets has long been considered advantageous in spatially heterogeneous environments, yet our understanding of how such traits relate to its widespread success and dominance is still limited. Using a dwarf bamboo, Sasa kurilensis, that often dominates cool‐temperate forest understorys, we investigated how population recovery over 20 years after an episodic die‐off may be augmented by clonal expansion via rhizomes. Previous analyses on genet demography using 9‐m2 plots showed that more productive genets were more likely to survive, spread laterally, and replace less productive ones. In this study, we examined whether the recovery of biomass in lower light microsites, where biomass recovery was initially slower, was supported by the spread of productive genets at larger scales, from surrounding higher‐light microsites. We found that the biomass recovery in lower‐light plots was more supported by genets that spread clonally into the plots. Such genets that spread from outside plots produced larger culms than those that had originally germinated there. Whereas genets that contributed much to the biomass of the low‐light plots spread extensively from higher‐light microsites, the spatial extent of genets that originally germinated in these plots was quite limited, so that the patterns of clonal expansion appeared to be unidirectional along the light gradient. Our findings suggest that clonal expansion of productive genets from higher‐light into shaded microsites may be important for S. kurilensis to proliferate across heterogeneous light environments.

Conservation of Schomburgkia crispa Lindl. (Orchidaceae) by reintroduction into a fragment of the Brazilian Cerrado

Asymbiotic germination of native orchids is an important technique for producing seedlings for use in species reintroduction programs, as it facilitates the maintenance of genetic variability. The objective of this study was to evaluate the adaptive responses of Schomburgkia crispa Lindl. (Orchidaceae) in an area undergoing environmental restoration, and to compare the efficacy of traditional and alternative substrates in order to contribute to the management and reintroduction of this species. Plants of S. crispa were obtained from asymbiotic sowing, and acclimated plants (ACP) were reintroduced in an underbrush area at the State University of Mato Grosso do Sul using three planting treatments: without substrate (WS); buriti stem substrate (BU); and, coconut fiber substrate (CF). Stress was assessed based on chlorophyll a fluorescence measurements and infrared thermography, and the growth environment was evaluated for light conditions and canopy cover. A completely randomized design was used with three treatments, each consisting of one substrate, with 10 single-plant replicates. After 850 days, fluorescence and survival of established plants (ESP) were re-evaluated. At 21 days after reintroduction, the plants showed 100% survival regardless of the substrate used, these values reached 73.3% for ESP plants. The largest variations between the temperature of the phorophytes and the temperature of the epiphytic orchid plants occurred on the day of reintroduction. There was no significant difference in the potential quantum efficiency of photosystem II (PSII: Fv/Fm) among treatments for ACP plants showed lower values of potential quantum efficiency (Fv/F0) to WS. Although the different substrates until 21 days did not significantly affect plant survival, temperature, or the photochemical efficiency of PSII, when ACP and ESP plants were compared, the quantum efficiency were significantly higher to acclimated plants indicating the better adjustment of the photosynthetic apparatus after 850 days justifying the high survival percentage. These data highlight the ability of S. crispa to resist in a heterogeneous light environment even through coming from asymbiotic sowing.

Seed size underlies the uncoupling in species composition between canopy and recruitment layers in European forests

Increasing evidence supports that canopy richness favors multifunctionality in European forests. Given that recruitment represents one of the main demographic bottlenecks in plant communities, the provision of similar levels of forest functioning in the future will depend on successful natural regeneration in the present. Here, we evaluated whether canopy diversity enhances recruitment (abundance and richness) by providing a more diverse seed supply and a more heterogeneous environmental context; or, alternatively, if post-dispersal environmental filters outweigh these expected positive effects. For this purpose, we used a large-scale European platform comprising 173 forest plots that follow a canopy species richness gradient (from monoculture to mixed plots up to 5 tree species) in five forest types from Mediterranean to boreal forests. Despite that canopy diversity promoted a more diverse seed supply and a more heterogeneous light environment, this did not translate into a richer or more abundant community of recruits. In fact, we found an important uncoupling in species composition between recruitment and canopy layers. Our results suggest that strong post-dispersal filters, mediated by an interaction between seed size and latitude, drive this mismatch. Large-seeded species were over-represented in the recruitment at both extremes of the European gradient (Mediterranean and boreal forests), while the opposite trend occurred at intermediate latitudes. Altogether, our work shows that preserving a more diverse canopy may not ensure successful recruitment, and advocates future studies analyzing the role of post-dispersal filters on the assembly of European forests.

Geographic variation in opsin expression does not align with opsin genotype in Lake Victoria cichlid populations.

Sensory adaptation to the local environment can contribute to speciation. Aquatic environments are well suited for studying this process: The natural attenuation of light through water results in heterogeneous light environments, to which vision‐dependent species must adapt for communication and survival. Here, we study visual adaptation in sympatric Pundamilia cichlids from southeastern Lake Victoria. Species with blue or red male nuptial coloration co‐occur at many rocky islands but tend to be depth‐differentiated, entailing different visual habitats, more strongly at some islands than others. Divergent visual adaptation to these environments has been implicated as a major factor in the divergence of P. pundamilia and P. nyererei, as they show consistent differentiation in the long‐wavelength‐sensitive visual pigment gene sequence (LWS opsin). In addition to sequence variation, variation in the opsin gene expression levels may contribute to visual adaptation. We characterized opsin gene expression and LWS genotype across Pundamilia populations inhabiting turbid and clear waters, to examine how different mechanisms of visual tuning contribute to visual adaptation. As predicted, the short‐wavelength‐sensitive opsin (SWS2b) was expressed exclusively in a population from clear water. Contrary to prediction however, expression levels of the other opsins were species‐ and island‐dependent and did not align with species differences in LWS genotype. Specifically, in two locations with turbid water, the shallow‐water dwelling blue species expressed more LWS and less RH2A than the deeper‐dwelling red species, while the opposite pattern occurred in the two locations with clear water. Visual modeling suggests that the observed distribution of opsin expression profiles and LWS genotypes does not maximize visual performance, implying the involvement of additional visual tuning mechanisms and/or incomplete adaptation.OPEN RESEARCH BADGE This article has earned an Open Data Badge for making publicly available the digitally‐shareable data necessary to reproduce the reported results. The data is available at https://hdl.handle.net/10411/I1IUUQ.

异质光照环境下克隆整合对南美蟛蜞菊和蟛蜞菊种间关系的影响

异质光照环境下克隆整合对南美蟛蜞菊和蟛蜞菊种间关系的影响

Relating Coral Skeletal Structures at Different Length Scales to Growth, Light Availability to Symbiodinium, and Thermal Bleaching

Light scattering of coral skeletons and tissues increases light availability to photosynthetic endosymbionts to form one of the most efficient biological collectors of solar radiation. Rapid increases in light availability during thermally-induced symbiont loss (bleaching) impair photosynthetic performance of the remaining Symbiodinium and precipitate a more severe bleaching response (optical feedback-loop hypothesis). Here we focus on light scattering of the skeleton, which is determined by light interaction with skeletal components assembled in a hierarchical fractal-like structure from tens of nanometers (e.g., calcium carbonate nanograins) to micro- and milli-meters (septa, corallites, and coenosteum) to centimeters and higher (colony form). We examined the association between skeletal structures, their role in light scattering, and species-specific bleaching responses for 88 coral species using phylogenetically-corrected analysis. We also explored the effect of growth on light scattering by modeling the fractal-like accretive growth of the skeleton (assuming a diffusion limited process of biomineralization) as a function of skeletal density, size of nanograins, fractal range of biomineralized clusters, and overall mass-fractal dimension, and validated the model with experimental data. Our results show that differences in light scattering from the top ~200µm (micro-μ_s^') of the skeleton, and not from the whole skeleton (bulk-μ_s^'), are related to bleaching susceptibility. We also demonstrate how differences in micro-μ_s^' of corallites and coenosteum could explain, in part, heterogeneous light environment between polyp and coenosarc. The average effective light transport distance of coenosteum measured in 14 coral species indicates that coenosteum could transport light to the corallites, which could then function as ‘light-trapping devices’ where photons are scattered multiple times by septa and corallite walls until absorbed by Symbiodinium. Furthermore, our fractal skeletal growth model suggests that corals that grow faster typically have lower mass-fractal dimension, denser skeletons, lower skeletal micro-μ_s^', and higher bleaching susceptibility. Finally, our results demonstrate that several skeletal structures of varying length scales known to modulate the light microenvironment of Symbiodinium in coral tissue are not associated with bleaching susceptibility. This work provides evidence of the relationship between skeletal growth, light scattering, and bleaching, and further supports the optical feedback-loop hypothesis of coral bleaching.

Midday Depression vs. Midday Peak in Diurnal Light Interception: Contrasting Patterns at Crown and Leaf Scales in a Tropical Evergreen Tree.

Crown architecture usually is heterogeneous as a result of foraging in spatially and temporally heterogeneous light environments. Ecologists are only beginning to identify the importance of temporal heterogeneity for light acquisition in plants, especially at the diurnal scale. Crown architectural heterogeneity often leads to a diurnal variation in light interception. However, maximizing light interception during midday may not be an optimal strategy in environments with excess light. Instead, long-lived plants are expected to show crown architectures and leaf positions that meet the contrasting needs of light interception and avoidance of excess light on a diurnal basis. We expected a midday depression in the diurnal course of light interception both at the whole-crown and leaf scales, as a strategy to avoid the interception of excessive irradiance. We tested this hypothesis in a population of guava trees (Psidium guajava L.) growing in an open tropical grassland. We quantified three crown architectural traits: intra-individual heterogeneity in foliage clumping, crown openness, and leaf position angles. We estimated the diurnal course of light interception at the crown scale using hemispheric photographs, and at the leaf scale using the cosine of solar incidence. Crowns showed a midday depression in light interception, while leaves showed a midday peak. These contrasting patterns were related to architectural traits. At the crown scale, the midday depression of light interception was linked to a greater crown openness and foliage clumping in crown tops than in the lateral parts of the crown. At the leaf scale, an average inclination angle of 45° led to the midday peak in light interception, but with a huge among-leaf variation in position angles. The mismatch in diurnal course of light interception at crown and leaf scales can indicate that different processes are being optimized at each scale. These findings suggest that the diurnal course of light interception may be an important dimension of the resource acquisition strategies of long-lived woody plants. Using a temporal approach as the one applied here may improve our understanding of the diversity of crown architectures found across and within environments.

Genet dynamics of a regenerating dwarf bamboo population across heterogeneous light environments in a temperate forest understorey.

Despite the advantage of plant clonality in patchy environments, studies focusing on genet demography in relation to spatially heterogeneous environments remain scarce. Regeneration of bamboos in forest understoreys after synchronous die‐off provides an opportunity for assessing how they come to proliferate across heterogeneous light environments. In a Japanese forest, we examined genet demography of a population of Sasa kurilensis over a 7‐year period starting 10 years after die‐off, shortly after which some genets began spreading horizontally by rhizomes. The aboveground biomass was estimated, and genets were discriminated in 9‐m2 plots placed under both canopy gaps and closed canopies. Overall, the results suggest that the survival and spread of more productive genets and the spatial expansion of genets into closed canopies underlie the proliferation of S. kurilensis. Compared to canopy gaps, the recovery rate of biomass was much slower under closed canopies for the first 10 years after the die‐off, but became accelerated during the next 7 years. Genet survival was greater for more productive genets (with greater initial number of culms), and the spaces occupied by genets that died were often colonized afterward by clonal growth of surviving genets. The number of genets decreased under canopy gaps due to greater mortality, but increased under closed canopies where greater number of genets colonized clonally from outside the plots than genets died. The colonizing genets were more productive (having larger culms) than those originally germinated within the plots, and the contribution of colonizing genets to the biomass was greater under closed canopies. Our study emphasizes the importance of investigating genet dynamics over relevant spatiotemporal scales to reveal processes underlying the success of clonal plants in heterogeneous habitats.

紫耳箭竹克隆形态可塑性对典型冠层结构及光环境的响应

PDF HTML阅读 XML下载 导出引用 引用提醒 紫耳箭竹克隆形态可塑性对典型冠层结构及光环境的响应 DOI: 10.5846/stxb201710161859 作者: 作者单位: 西南大学生命科学学院，三峡库区生态环境教育部重点实验室,西南大学生命科学学院，三峡库区生态环境教育部重点实验室,西南大学生命科学学院，三峡库区生态环境教育部重点实验室,西南大学生命科学学院，三峡库区生态环境教育部重点实验室,西南大学生命科学学院，三峡库区生态环境教育部重点实验室,西南大学生命科学学院，三峡库区生态环境教育部重点实验室,三峡库区生态环境教育部重点实验室，西南大学生命科学学院 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金项目（31570612） Response of clonal morphological plasticity of Fargesia decurvata to different forest canopy structures and light conditions Author: Affiliation: Key Laboratory of Eco-Environments in Three Gorges Reservoir Region, School of Life Science, Southwest University,,,,,,Key Laboratory of Eco-Environments in Three Gorges Reservoir Region, School of Life Science, Southwest University Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:在重庆金佛山国家自然保护内，选择了3种典型群落类型（落叶阔叶林、常绿落叶阔叶混交林和常绿阔叶林），使用Hemiview数字植物冠层分析系统量化群落冠层结构和光环境特征，并对林下紫耳箭竹（Fargesia decurvata）的形态可塑性特征进行调查，分析冠层结构和光环境特征改变下紫耳箭竹形态可塑性的差异，并探讨它们之间的相互关系。结果表明：（1）随着落叶阔叶林→常绿落叶阔叶混交林→常绿阔叶林演替的进行，群落的冠层开度降低，叶面积指数增加，平均叶倾角变小，趋于水平化，冠层对光的截获能力提高，林下光照的强度降低（P < 0.05）。（2）随着光照强度的降低，紫耳箭竹分株矮小化，叶片变窄，生物量积累降低，但通过增大比茎长、叶面积率和比叶面积提高对光的利用效率，并增大分枝角度和比隔长有效适应弱光环境。（3）在光照条件差的常绿阔叶林下，紫耳箭竹降低对地下茎的投资，将较多的生物量用于秆的增高增长和叶片的生长；而在光照条件好的落叶阔叶林环境下，紫耳箭竹降低对枝、叶生物量的分配，则加大对地下茎的投资，可认为是克隆植物对水分资源所表现的一种觅食行为。研究表明，紫耳箭竹种群随着冠层结构的改变发生了明显的可塑性变化，这些可塑性变化是种群对冠层结构和光环境差异的适应性反应的结果，有利于增强种群对异质生境中光资源的获取和利用；群落内部可以通过调控冠层结构的改变协调和控制小径竹种群的发展。 Abstract:Clonal morphological plasticity, closely related to the maintenance and regeneration of populations, is the ability for a plant to adapt to a changing environment. In a field experiment, the Hemiview digital canopy analysis system was used to measure the canopy structures (canopy openness, CO; leaf area index, LAI; mean leaf angle, MLA) and light conditions (direct solar radiation under canopy, Dir; diffuse solar radiation under canopy, Dif; Total solar radiation under canopy, Tot) in three typical forest types (deciduous broad-leaved forest, evergreen and deciduous broad-leaved mixed forest, evergreen broad-leaved forest) in Jinfo Mountains National Nature Reserve, Chongqing. The clonal morphological plasticity of understory dwarf bamboo, Fargesia decurvata, was also measured. Moreover, the relationship between canopy structure and morphological plasticity of F. decurvata was discussed. The results showed that:(1) With the development of forest succession, the CO and MLA decreased, but LAI increased, resulting in the increase in light interception capability of forest canopy and the decrease in the light intensity under forest canopy (P < 0.05). (2) Forest canopy condition had a significant effect on the morphological plasticity of F. decurvata ramets. With the decrease in light intensity, the culm height, basal diameter, leaf area, and biomass of F. decurvata ramets decreased. However, decreased light intensity can increase the specific culm length, leaf area ratio, and specific leaf area to improve the utilization efficiency of light and increase the branch angle of spacer and specific spacer length to adapt to low light environments. (3) Under the low light environment in an evergreen broad-leaved forest, F. decurvata reduced its investment in rhizome but allocated more biomass for culm and leaf growth. However, in the deciduous broad-leaved forest, F. decurvata reduced the allocation of branches and leaves and increased the investment in rhizome growth (spacer length and diameter), which can be considered as a foraging behavior to searching much more water resources. These results suggested that the morphological plasticity of F. decurvata underwent significant change in different forest canopies, which is the result of adaptive response to different forest canopy structures and light conditions and enhances the ability to acquire and utilize light resources in heterogeneous light environments. Moreover, the communities may be able to coordinate and control the development of dwarf bamboo by controlling the change of canopy structures and light conditions. 参考文献 相似文献 引证文献