1
|
Liu X, Man X, Chen M, Zhao C, Liu C, Tong J, Meng F, Shao M, Qu B. Transgenerational plasticity in morphological characteristics and biomass of the invasive plant Xanthium strumarium. ECOLOGICAL APPLICATIONS : A PUBLICATION OF THE ECOLOGICAL SOCIETY OF AMERICA 2024; 34:e2920. [PMID: 37750229 DOI: 10.1002/eap.2920] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/06/2022] [Revised: 08/02/2023] [Accepted: 08/29/2023] [Indexed: 09/27/2023]
Abstract
Transgenerational plasticity (TGP) allows a plant to acclimate to external variable environments and is a potential mechanism that explains the range expansion and invasion success of some exotic plants. Most studies explored the traits of TGP associated with the success of exotic plant invasions by comparison studies among exotic, native, invasive, and noninvasive species. However, studies on the TGP of invasive plants in different resource environments are scarce, and the biological mechanisms involved are not well understood. This study aimed to determine the role of TGP in the invasiveness of Xanthium strumarium in northeast China. We measured the plant morphology of aboveground parts and the growth of three generations of the invader under different environmental conditions. The results showed that the intergenerational plasticity of X. strumarium was stronger under stress conditions. We found that the X. strumarium parent generation (F0) grown under water and/or nutrient deficiency conditions transferred the environmental information to their offspring (F1 and F2). The F1 generation grown under high-resource conditions has greater height with larger crown sizes, thicker basal diameters, and higher biomass. Both water and nutrients can affect the intergenerational transmission of plant plasticity, nutrients play a more important role compared with water. The high morphological intergenerational plasticity of X. strumarium under a pressure environment can help it quickly adapt to the new environment and accelerate the rapid expansion of the population in the short term. The root:shoot ratio and reproductive and nutrient distribution of the X. strumarium F0 and F1 generations showed high stability when the growth environment of the F0 generation differed from that of the F1 generation. The stable resource allocation strategy can ensure that the obtained resources are evenly distributed to each organ to maintain the long-term existence of the community. Therefore, the study of intergenerational transmission plasticity is of great significance for understanding the invasion process, mechanism, and prevention of invasive plants.
Collapse
Affiliation(s)
- Xinyue Liu
- Liaoning Key Laboratory of Biological Invasions and Global Changes, Shenyang Agricultural University, Shenyang, China
| | - Xiaozhen Man
- Liaoning Key Laboratory of Biological Invasions and Global Changes, Shenyang Agricultural University, Shenyang, China
| | - Meishan Chen
- Liaoning Key Laboratory of Biological Invasions and Global Changes, Shenyang Agricultural University, Shenyang, China
| | - Changxin Zhao
- Liaoning Key Laboratory of Biological Invasions and Global Changes, Shenyang Agricultural University, Shenyang, China
| | - Chuang Liu
- Liaoning Key Laboratory of Biological Invasions and Global Changes, Shenyang Agricultural University, Shenyang, China
| | - Jialin Tong
- Liaoning Key Laboratory of Biological Invasions and Global Changes, Shenyang Agricultural University, Shenyang, China
| | - Fanqi Meng
- Liaoning Key Laboratory of Biological Invasions and Global Changes, Shenyang Agricultural University, Shenyang, China
| | - Meini Shao
- Liaoning Key Laboratory of Biological Invasions and Global Changes, Shenyang Agricultural University, Shenyang, China
| | - Bo Qu
- Liaoning Key Laboratory of Biological Invasions and Global Changes, Shenyang Agricultural University, Shenyang, China
- Liaoning Panjin Wetland Ecosystem National Observation and Research Station, Shenyang, China
| |
Collapse
|
2
|
Earley TS, Feiner N, Alvarez MF, Coolon JD, Sultan SE. The relative impact of parental and current environment on plant transcriptomes depends on type of stress and genotype. Proc Biol Sci 2023; 290:20230824. [PMID: 37752834 PMCID: PMC10523085 DOI: 10.1098/rspb.2023.0824] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2023] [Accepted: 08/30/2023] [Indexed: 09/28/2023] Open
Abstract
Through developmental plasticity, an individual organism integrates influences from its immediate environment with those due to the environment of its parents. While both effects on phenotypes are well documented, their relative impact has been little studied in natural systems, especially at the level of gene expression. We examined this issue in four genotypes of the annual plant Persicaria maculosa by varying two key resources-light and soil moisture-in both generations. Transcriptomic analyses showed that the relative effects of parent and offspring environment on gene expression (i.e. the number of differentially expressed transcripts, DETs) varied both for the two types of resource stress and among genotypes. For light, immediate environment induced more DETs than parental environment for all genotypes, although the precise proportion of parental versus immediate DETs varied among genotypes. By contrast, the relative effect of soil moisture varied dramatically among genotypes, from 8-fold more DETs due to parental than immediate conditions to 10-fold fewer. These findings provide evidence at the transcriptomic level that the relative impacts of parental and immediate environment on the developing organism may depend on the environmental factor and vary strongly among genotypes, providing potential for the interplay of these developmental influences to evolve.
Collapse
Affiliation(s)
- Timothy S. Earley
- Biology Department, Wesleyan University, 52 Lawn Avenue, Middletown, CT 06459, USA
| | | | - Mariano F. Alvarez
- Biology Department, Wesleyan University, 52 Lawn Avenue, Middletown, CT 06459, USA
| | - Joseph D. Coolon
- Biology Department, Wesleyan University, 52 Lawn Avenue, Middletown, CT 06459, USA
| | - Sonia E. Sultan
- Biology Department, Wesleyan University, 52 Lawn Avenue, Middletown, CT 06459, USA
| |
Collapse
|
3
|
Yan Z, Tian D, Han W, Ji C, Hou X, Guo Y, Fang J. Weak transgenerational effects of ancestral nitrogen and phosphorus availabilities on offspring phenotypes in Arabidopsis thaliana. JOURNAL OF PLANT RESEARCH 2023; 136:515-525. [PMID: 37055608 DOI: 10.1007/s10265-023-01456-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/11/2022] [Accepted: 03/29/2023] [Indexed: 06/09/2023]
Abstract
Nutrient availability significantly regulates plant growth and metabolic functions, but whether and how the long-term exposure of ancestral plants to contrasting nutrient environments influences offspring phenotypic performance (i.e., transgenerational plasticity) remain poorly addressed. Here we conducted experimental manipulations using Arabidopsis thaliana with the ancestral plants grown in different nitrogen (N) and phosphorus (P) availabilities over eleven consecutive generations, and then examined the offspring phenotypic performance under the interactive effects of current and ancestral nutrient environments. We found that current rather than ancestral nutrient environments dominantly explained the variations in offspring plant traits (i.e., flowering time, aboveground biomass and biomass allocation fractions), suggesting the relatively weak transgenerational effects of ancestral N and P availabilities on offspring phenotypes. In contrast, increasing N and P availabilities in the offspring generation remarkably shortened the flowering time, increased the aboveground biomass, and altered biomass allocation fractions differentially among organs. Despite the overall weak transgenerational phenotypic plasticity, under the low nutrient environment, the offspring of ancestral plants from the low nutrient environment had a significantly higher fruit mass fraction than those from the suitable nutrient environment. Taken together, our findings suggest that A. thaliana exhibits a much stronger within- than trans-generational trait plasticity under contrasting nutrient availabilities, and may provide important insights into the understanding of plant adaptation and evolutionary processes under changing nutrient environments.
Collapse
Affiliation(s)
- Zhengbing Yan
- State Key Laboratory of Vegetation and Environmental Change, Institute of Botany, Chinese Academy of Sciences, Xiangshan, Beijing, 100093, China.
- Institute of Ecology, College of Urban and Environmental Sciences, Peking University, Beijing, 100871, China.
| | - Di Tian
- The Key Laboratory for Silviculture and Conservation of Ministry of Education, Beijing Forestry University, Beijing, 100083, China.
| | - Wenxuan Han
- Key Laboratory of Plant-Soil Interactions of the Ministry of Education, College of Resources and Environmental Sciences, China Agricultural University, Beijing, 100193, China
| | - Chengjun Ji
- State Key Laboratory of Vegetation and Environmental Change, Institute of Botany, Chinese Academy of Sciences, Xiangshan, Beijing, 100093, China
| | - Xinghui Hou
- State Key Laboratory of Systematic and Evolutionary Botany, Institute of Botany, Chinese Academy of Sciences, Beijing, 100093, China
| | - Yalong Guo
- State Key Laboratory of Systematic and Evolutionary Botany, Institute of Botany, Chinese Academy of Sciences, Beijing, 100093, China
| | - Jingyun Fang
- Institute of Ecology, College of Urban and Environmental Sciences, Peking University, Beijing, 100871, China
| |
Collapse
|
4
|
Dos Santos AS, Braz MIG, Dos Santos de Barros C, de Cássia Quitete Portela R, de Mattos EA. Sensitivity of seed germination to water stress in high-altitude populations of a threatened palm species. PLANT BIOLOGY (STUTTGART, GERMANY) 2023; 25:593-602. [PMID: 37029605 DOI: 10.1111/plb.13527] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/06/2022] [Accepted: 03/08/2023] [Indexed: 05/17/2023]
Abstract
Divergence in seed germination patterns among populations of the same species is important for understanding plant responses to environmental gradients and potential plant sensitivity to climate change. In order to test responses to flooding and decreasing water potentials, over 3 years we germinated and grew seeds from three habitats of Euterpe edulis Mart. occurring along an altitudinal gradient. Seed germination and root growth were evaluated under different water availability treatments: control, flood, -0.4 MPa, -0.8 MPa, in the years 2012, 2013 and 2014, and in the final year of the experiment (2014) at -1.0 MPa and -1.5 MPa. Seeds from the montane habitat did not germinate in the flooding treatment. Seed germination of all three habitats decreased in the -1.5 MPa treatment and the montane habitat had lowest germination in this treatment. Time required for half of the seeds to germinate increased up to -0.8 MPa. Seeds from montane habitats germinated more slowly in all treatments. The only difference in seed germination synchrony was an increase in the submontane population under the flooding treatment. However, synchrony decreased at the lowest water potentials. Roots of the montane population were more vigorous in most treatments, except at -0.8 MPa. The unusual ability of these seeds to germinate at low water potentials might be related to early seed germination at the onset of the rainy season, which potentially decreases seed predation pressure. Seeds of the montane population were more sensitive to both types of water stress. A predicted increase in the frequency and intensity of extreme high rainfall or drought events may predispose early stages of this population to adverse factors that might negatively affect population viability with elevational in future climate change scenarios.
Collapse
Affiliation(s)
- A S Dos Santos
- Laboratório de Ecologia Vegetal, Programa de Pós-Graduação em Ecologia, Instituto de Biologia, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil
| | - M I G Braz
- Laboratório de Ecologia Vegetal, Programa de Pós-Graduação em Ecologia, Instituto de Biologia, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil
| | - C Dos Santos de Barros
- Laboratório de Vertebrados, Programa de Pós-Graduação em Ecologia, Instituto de Biologia, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil
| | - R de Cássia Quitete Portela
- Laboratório de Ecologia Vegetal, Departamento de Ecologia, Instituto de Biologia, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil
| | - E A de Mattos
- Laboratório de Ecologia Vegetal, Departamento de Ecologia, Instituto de Biologia, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil
| |
Collapse
|
5
|
Paravar A, Maleki Farahani S, Rezazadeh A. Morphological, physiological and biochemical response of L allemantia species to elevated temperature and light duration during seed development. Heliyon 2023; 9:e15149. [PMID: 37123928 PMCID: PMC10133671 DOI: 10.1016/j.heliyon.2023.e15149] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2022] [Revised: 03/27/2023] [Accepted: 03/28/2023] [Indexed: 05/02/2023] Open
Abstract
Seed weight, storability, and germinability can depend on maternal plant's environment. However, there is slight information about the effect of light and temperature on seed quality of Lallemantia species. The purpose of this research was to determine the properties of physio-biochemical of maternal plant, seed quality, and seed chemical composition of Lallemantia species (Lallemantia iberica and Lallemantia royleana) under temperature (15 °C, 25 °C, and 35 °C) and photoperiod (8 hd-1, 16 hd-1, and 24 hd-1) maternal plants environment. Increasing temperature and photoperiod caused a reduction in leaf chlorophyll, stomatal movement, total soluble sugar, superoxide dismutase (SOD), catalase (CAT), and ascorbate peroxidase (APX) enzymes activities, and an increment in malondialdehyde (MDA) and hydrogen peroxide (H2O2) content of seeds. However, the highest weight, germination, vigor index, and longevity, seed chemical compositions were obtained in offspring which matured under 25 °C for 16 hd-1. The highest germination, oil, and relative percentage of fatty acids (oleic acid (OA), linoleic acid (LA), and linolenic acid (LNA)) were obtained in L. iberica seeds. On the contrary, longevity, mucilage, and sucrose were more abundant in L. royleana seeds. Overall, this research has clearly shown that temperature and light quality and quantity of maternal plant's environment have an immensely effect on producing of seeds with high-quality. However, it is necessary to investigate the impact of the epigenetic mechanisms of the maternal plant on the offspring in future studies.
Collapse
Affiliation(s)
- Arezoo Paravar
- Department of Crop Production and Plant Breeding, College of Agriculture, Shahed University, Tehran, Iran
| | - Saeideh Maleki Farahani
- Department of Crop Production and Plant Breeding, College of Agriculture, Shahed University, Tehran, Iran
- Corresponding author.
| | - Alireza Rezazadeh
- Department of Plant Protection, College of Agriculture, Shahed University, Tehran, Iran
| |
Collapse
|
6
|
Morgan BL, Donohue K. Parental methylation mediates how progeny respond to environments of parents and of progeny themselves. ANNALS OF BOTANY 2022; 130:883-899. [PMID: 36201313 PMCID: PMC9758305 DOI: 10.1093/aob/mcac125] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/01/2022] [Accepted: 10/04/2022] [Indexed: 06/16/2023]
Abstract
BACKGROUND AND AIMS Environments experienced by both parents and offspring influence progeny traits, but the epigenetic mechanisms that regulate the balance of parental vs. progeny control of progeny phenotypes are not known. We tested whether DNA methylation in parents and/or progeny mediates responses to environmental cues experienced in both generations. METHODS Using Arabidopsis thaliana, we manipulated parental and progeny DNA methylation both chemically, via 5-azacytidine, and genetically, via mutants of methyltransferase genes, then measured progeny germination responses to simulated canopy shade in parental and progeny generations. KEY RESULTS We first found that germination of offspring responded to parental but not seed demethylation. We further found that parental demethylation reversed the parental effect of canopy in seeds with low (Cvi-1) to intermediate (Col) dormancy, but it obliterated the parental effect in seeds with high dormancy (Cvi-0). Demethylation did so by either suppressing germination of seeds matured under white-light (Cvi-1) or under canopy (Cvi-0), or by increasing the germination of seeds matured under canopy (Col). Disruption of parental methylation also prevented seeds from responding to their own light environment in one genotype (Cvi-0, most dormant), but it enabled seeds to respond to their own environment in another genotype (Cvi-1, least dormant). Using mutant genotypes, we found that both CG and non-CG DNA methylation were involved in parental effects on seed germination. CONCLUSIONS Parental methylation state influences seed germination more strongly than does the progeny's own methylation state, and it influences how seeds respond to environments of parents and progeny in a genotype-specific manner.
Collapse
Affiliation(s)
- Britany L Morgan
- University Program in Ecology Duke University, Durham, NC 27705, USA
- Center for Agricultural Synthetic Biology, University of Tennessee, Knoxville, TN 37996, USA
| | - Kathleen Donohue
- University Program in Ecology Duke University, Durham, NC 27705, USA
- Biology Department, Duke University, Durham, NC 27705, USA
| |
Collapse
|
7
|
Long-Term Maternal Fertilizer Addition Increased Seed Size but Decreased Germination Capacity and Offspring Performance in Taxus baccata L. FORESTS 2022. [DOI: 10.3390/f13050670] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Plant fitness and species persistence depend on seed quantity and their ability to germinate and produce viable offspring. Although maternal environment can have a great impact on seed quality, few studies are pointing to the transgenerational effect of maternal environment on germination rate and offspring traits. Moreover, global changes connected to nitrogen and phosphorus deposition can also impact plants’ reproductive performance. Here, we collected Taxus baccata L. seeds produced by the same genotype female plants grown in different nutritional regimes. We use them to analyze seed size and the impact of long-term fertilization on germination capacity and offspring traits. Our results show that long-term maternal fertilizer addition increases the ratio of large seeds produced, but at the same time decreases germination capacity compared to control and nonfertilized plants. Moreover, it was demonstrated that maternal environment impacts seed traits and germination rate, and seed mass rather than maternal environment impacts offspring performance. Therefore, the study provides information on how the maternal environment regulates seed traits and germination capacity as well as seedling growth to adapt to increased nitrogen and phosphorus deposition and improves prediction about plants’ response to global environmental changes.
Collapse
|
8
|
Zettlemoyer MA, Lau JA. Warming during maternal generations delays offspring germination in native and nonnative species. OIKOS 2021. [DOI: 10.1111/oik.08345] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Affiliation(s)
- Meredith A. Zettlemoyer
- Kellogg Biological Station, Michigan State Univ. Hickory Corners MI USA
- Dept of Plant Biology, Michigan State Univ. East Lansing MI USA
- Dept of Plant Biology, Univ. of Georgia Athens GA USA
| | - Jennifer A. Lau
- Kellogg Biological Station, Michigan State Univ. Hickory Corners MI USA
- Dept of Plant Biology, Michigan State Univ. East Lansing MI USA
- Dept of Biology&Environmental Resilience Inst., Indiana Univ. Bloomington IN USA
| |
Collapse
|
9
|
Alvarez M, Bleich A, Donohue K. Genetic differences in the temporal and environmental stability of transgenerational environmental effects. Evolution 2021; 75:2773-2790. [PMID: 34586633 DOI: 10.1111/evo.14367] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2020] [Revised: 05/31/2021] [Accepted: 06/29/2021] [Indexed: 12/14/2022]
Abstract
Environments influence the expression of phenotypes of individuals, their progeny, and even their grandprogeny. The duration of environmental effects and how they are modified by subsequent environments are predicted to be targets of natural selection in variable environments. However, little is known about the genetic basis of the temporal persistence of environmental effects and their stability of expression across subsequent environments, or even the extent to which natural genotypes differ in these attributes of environmental effects. We factorially manipulated the thermal environment experienced in three successive generations, to quantify the temporal persistence and environmental stability of temperature effects in contrasting genotypes of Arabidopsis thaliana. We found that genotypes differed in the manner in which environmental effects dissipated across successive generations, the manner in which responses to ancestral environments were stably expressed in present environments, the manner in which ancestral environments altered responses to present environments, and in the manner in which ancestral environments altered fitness in present conditions. Genetic variation exists in nature for these trait-specific environmental responses, suggesting that the temporal persistence and stability of environmental effects in variable environments have the potential to evolve in response to natural selection imposed by different environments and sequences of environments.
Collapse
Affiliation(s)
| | - Andrew Bleich
- Department of Biology, Duke University, Durham, North Carolina, 27708
| | - Kathleen Donohue
- Department of Biology, Duke University, Durham, North Carolina, 27708
| |
Collapse
|
10
|
Alvarez M, Bleich A, Donohue K. Genotypic variation in the persistence of transgenerational responses to seasonal cues. Evolution 2020; 74:2265-2280. [PMID: 32383475 DOI: 10.1111/evo.13996] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2019] [Revised: 04/09/2020] [Accepted: 04/26/2020] [Indexed: 01/01/2023]
Abstract
Phenotypes respond to environments experienced directly by an individual, via phenotypic plasticity, or to the environment experienced by ancestors, via transgenerational environmental effects. The adaptive value of environmental effects depends not only on the strength and direction of the induced response but also on how long the response persists within and across generations, and how stably it is expressed across environments that are encountered subsequently. Little is known about the genetic basis of those distinct components, or even whether they exhibit genetic variation. We tested for genetic differences in the inducibility, temporal persistence, and environmental stability of transgenerational environmental effects in Arabidopsis thaliana. Genetic variation existed in the inducibility of transgenerational effects on traits expressed across the life cycle. Surprisingly, the persistence of transgenerational effects into the third generation was uncorrelated with their induction in the second generation. Although environmental effects for some traits in some genotypes weakened over successive generations, others were stronger or even in the opposite direction in more distant generations. Therefore, transgenerational effects in more distant generations are not merely caused by the retention or dissipation of those expressed in prior generations, but they may be genetically independent traits with the potential to evolve independently.
Collapse
Affiliation(s)
- Mariano Alvarez
- Department of Biology, Duke University, Durham, North Carolina, 27708
| | - Andrew Bleich
- Department of Biology, Duke University, Durham, North Carolina, 27708
| | - Kathleen Donohue
- Department of Biology, Duke University, Durham, North Carolina, 27708
| |
Collapse
|
11
|
Serianthes nelsonii Seed Germination and Seedling Behavior are Minimally Influenced by Chemical and Light Treatment. HORTICULTURAE 2019. [DOI: 10.3390/horticulturae5020031] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
The role of seed imbibition and light during germination are not known for the critically endangered Serianthes nelsonii Merr. Scarified seeds were pre-soaked in gibberellic acid (GA3) up to 300 mg/L and nitrate solutions of 3000 mg/L to determine if germination was influenced by these treatments. Scarified and imbibed seeds were incubated in high red:far red and low red:far red light to determine the influence of light quality on germination traits. The GA3 and nitrate treatments did not influence germination percentage or timing, but did increase the height of newly emerged seedlings. Moreover, GA3 extended the longevity of cotyledons and shortened the window of time that seedlings required to resume height growth. These growth responses were not sustained, and all seedlings reached heights of 30 cm at a similar number of weeks. The light treatments did not influence any of the germination response traits. The results indicate that imbibing seeds with chemical solutions and providing light in a range of light quality treatments exerted a minimal influence on S. nelsonii seed germination behaviors. Imbibing seeds with water and germinating in darkness is sufficient for achieving the germination of this endangered tree species.
Collapse
|