Knowledge Resource Center for Ecological Environment in Arid Area
| 角果碱蓬种子异型性对盐渍化环境的适应意义 | |
| 其他题名 | Adaptive significance of a seed-heteromorphic species Suaeda corniculata in saline habitats |
| 杨帆 | |
| 出版年 | 2015 |
| 学位类型 | 博士 |
| 导师 | 黄振英 |
| 学位授予单位 | 中国科学院大学 |
| 中文摘要 | 植物能够采取不同的生活史策略来应对生长环境的异质性。盐生植物在盐渍化生境中生存和繁衍，生活史各个阶段都必须经受严酷环境的考验。具有异型种子的植物物种在盐生环境中较为常见，且异型种子不同的生态学特性被认为有利于其适应异质环境。因此，盐生环境中异型种子植物是检验生活史策略假说的理想材料。本研究以生长在内蒙古鄂尔多斯毛乌素沙地盐渍化生境中的异型种子植物角果碱蓬(Suaeda corniculata)为研究对象，通过野外调查和控制实验相结合的生态学方法，探究了盐渍化生境中关键的环境因子对异型种子休眠和萌发特性以及植株生长和繁殖的影响，揭示了异型种子物种在温带半干旱区盐生环境中的生活史适应对策。得到以下主要结果： 1、对角果碱蓬二型种子形态、休眠和萌发特性开展对比研究，测定了二型种子休眠和萌发行为对温度、光照和盐分(NaCl)的响应，结果表明：(1)二型种子(棕色和黑色异型种子)在大小、种皮特性和结实比例方面有显著差异。与黑色种子相比，棕色种子个体较大，种皮透水性强。黑色种子与棕色种子的结实比例约为5.6 : 1。(2)新成熟的棕色种子的萌发对各温度梯度和光照条件不敏感，萌发率较高(84–100%)；而新成熟的黑色种子萌发率较低(8–78%)，萌发对光照敏感。(3)黑色种子具有浅度生理休眠，种皮划破、赤霉素处理和低温层积均可有效地提高种子的萌发率。(4)与黑色种子相比，棕色种子的耐盐性强，在较高的盐分浓度下仍有较高的萌发率。低温层积处理能够降低黑色种子对盐胁迫的敏感性，有效地提高种子的初始萌发率、萌发恢复率和最终萌发率。角果碱蓬二型种子不同的形态、休眠和萌发特性有助于该种群在盐渍化生境中选择相对适宜的萌发时机和有利的生长环境。 2、角果碱蓬生活史和种子特性对萌发物候的影响具有表型可塑性。与早萌发的植株相比，晚萌发的角果碱蓬二型种子所形成的植株具有较少的生物量和种子产出，但可以产生较高的棕色种子比例(晚萌发为99.5%，早萌发为60.7%)，而且棕色种子随着植株萌发时间的延后而增大20%。棕色种子的幼苗建成时间比黑色种子的短2–6天。晚萌发的棕色种子比晚萌发的黑色种子产生更大的植株。棕色种子比例的增加可以使得子代避免经历母代因萌发推迟而无法完成生活史的命运。角果碱蓬通过调节异型种子比例来减轻晚萌发所带来的不利影响，有利于种群在不可预测生境的维持和更新。 3、角果碱蓬生活史和种子特性对土壤盐分的影响具有表型可塑性。土壤盐分胁迫抑制了植株生长和种子产出，但是植株的繁殖分配和棕色种子结实比例随着盐分浓度的升高而增加。母体的高盐环境降低了黑色种子萌发率，而对棕色种子萌发没有影响。这些可塑性表现可能是种群对盐生环境长期适应的结果。生长在较高土壤盐分(0.66 mol?L–1)地区的种群比生长在较低土壤盐分(0.41 mol?L–1)地区的种群植株小12 cm、繁殖分配高3%、棕色种子结实比例高47%以及黑色种子萌发率低45%。土壤盐分的异质性很可能是导致不同种群的种子特性产生遗传和表型差异的环境因素之一。 4、角果碱蓬子代植株的繁殖分配、种子结实比例和黑色种子萌发率具有代间可塑性(即子代特征受到母代的萌发时间和土壤盐分的影响)。来自于晚萌发母代的子代植株比来自早萌发母代的子代植株具有相对较高的繁殖分配和较低的棕色种子比例。与母代土壤盐分环境一致的子代比与母代土壤环境不同的子代具有更高的繁殖分配。当子代植株生长在有利的环境(早萌发或低盐分)中时，母代的胁迫环境(晚萌发或高盐分)会使得子代结实的黑色种子萌发率升高。种子异型性的代间效应为物种的更新策略提供了生态多样性，促进了后代对时空变化环境的适应，有利于种群的维持。 异型种子植物角果碱蓬生活史适应对策案例研究表明：(1)二型种子休眠和萌发特性属于“两头下注”策略；(2)植株生物量分配和二型种子结实比例的可塑性以及母体环境效应决定了角果碱蓬生活史格局；(3)具有适应意义母体效应和代间可塑性在生态适应方面起着重要的作用。因此，种子异型性在角果碱蓬的生活史对策中扮演重要的生态角色，增大了该物种的对异质环境的适应性，从而使其种群能够在盐渍化生境中得以维持、更新和发展。 |
| 英文摘要 | Diverse life history strategies enable plants to cope with environmental heterogeneity. Life history of halophytes experiences severe environmental conditions in the saline habitat. Seed-heteromorphic species is known to be prevalent in saline areas and different ecological characteristics between seed morphs provide an advantage in adaptation to heterogeneous environments. Therefore, species with heteromorphic seeds are ideal materials to test hypotheses of plant life history strategies. This dissertation presents a case study of a seed-dimorphic species Suaeda corniculata, an annual halophyte growing on a saline steppe in northwest China. The influences of key environmental factors in saline habitats on seed dormancy/germination and plant growth/reproduction were determined by combined method of field survey and controlled trials to explain the adaptive life history strategies of seed-heteromorphic species in the saline habitat. The main results showed as follows: 1. We compared the morphology, dormancy and germination characteristics of dimorphic seeds of S. corniculata, and the seeds were incubated in different temperature regimes, light and salinity (NaCl) conditions to determine their germination responses to this conditions. Dimorphic seeds were different in seed mass and testa morphology. Brown seeds were bigger and more permeable to water than black seeds. Seed ratio was 5.6 : 1 (black seeds : brown seeds). Freshly matured brown seeds were insensitive to temperature or light and had a high germination percentage (84–100%) in all temperature regimes and under either light or dark conditions. By contrast, black seeds had a lower germination percentage (8–78%) than brown seeds in all temperature regimes, and germination increased in light. Seed coat scarification, GA3 treatments and cold stratification significantly increased the germination of black seeds, suggesting that black seeds had non-deep physiological dormancy. Responses of dimorphic seeds to saline stress were different. Brown seeds were more salt-tolerant than black seeds and germinated to a high germination percentage in high salt concentrations. Cold stratification reduced the sensitivity of black seeds to salt stress and increased the initial, recovery and final germination in salt solutions. The differences in morphology, dormancy and germination characteristics between dimorphic seeds of S. corniculata may help this species to choose the right time to germinate and favourable conditions to grow. 2. Seed characteristics and life history traits of S. corniculata are phenotypically plastic to the variation of germination timing. Germinated seeds sown late in the year produced smaller plants with fewer seeds that had a higher proportion of non-dormant brown seeds than those sown early in the year (99.5% vs. 60.7%, late vs. early), and size of brown seeds increased by 20% with the delay of sowing date. The length of the seedling stage for brown seeds was 2–6 d shorter than that for black seeds. Late-germinating brown seeds produced larger plants than late-germinating black seeds. An increasing proportion of brown seeds may enable the progeny from late-germinating plants to escape the fate (unable to complete life cycle) of their parent plants. Altering the proportion of the two seed types in response to germination timing can help alleviate the adverse effects of delayed germination and may favor the maintenance and regeneration of the population in its unpredictable environment. 3. Seed characteristics and life history traits of S. corniculata were plastic to salt. Plants grown at high soil salinity produced small plants with fewer seeds, but reproductive allocation and proportion of non-dormant brown seeds increased with the increase of salt concentration. High maternal salinity reduced germination percentage of black seeds but had no effect on brown seeds. This plasticity appeared to be rooted in inherent adaptation of different populations to the salinity in their habitat. Compared with population grew in the site with relatively low soil salinity (0.41 mol?L–1), the population grew in the site with high soil salinity (0.66 mol?L–1) had smaller plants (44 cm vs. 56 cm) with higher reproductive allocation (25% vs. 22%), and produced higher proportion of brown seeds (67% vs. 20%) and lower germination percentage of black seeds (35% vs. 80%). Soil salinity may induce both inherent and phenotypic differentiation of seed traits between populations in saline habitats. 4. Reproductive allocation, seed morph ratio and germination of black seeds had transgenerational plasticity (these traits of offspring were influenced by germination timing and soil salinity experienced by maternal generation). Progeny plants from late-germinating mothers allocated to reproduction and produced fewer brown seeds than those from early-germinating mothers. Progeny plants that grew under the same salinity as their mothers had higher reproductive allocation than those that grew in contrasting conditions. When progeny plants were grown in favourable conditions (early germination or low salinity), the stressful maternal conditions (late germination or high salinity) increased germination of black seeds. Thus, transgenerational plasticity provided an ecological diversity in the regenerative strategy for seed heteromorphic species, and it may contribute to population maintenance via enabling adaptive responses of offspring to temporal and spatial variations. The case study of life history adaptive strategy of seed heteromorphic species S. corniculata showed that: (1) dormancy and germination characteristics of dimorphic seeds can be viewed as bet-hedging strategy; (2) phenotypic plasticity in biomass allocation and seed morph ratio and maternal environmental effect determines the life history pattern; and (3) adaptive maternal and transgenerational effects are important to ecological adaptation. Therefore, seed heteromorphism plays an important role in life history strategies of S. corniculata in response to environmental heterogeneity and ensures successful population maintenance, regeneration and development of S. corniculata in the saline habitat. |
| 中文关键词 | 生活史策略 ; 母体效应 ; 表型可塑性 ; 盐生生境 ; 种子异型性 |
| 英文关键词 | life history strategy maternal effects phenotypic plasticity saline habitat seed heteromorphism |
| 语种 | 中文 |
| 国家 | 中国 |
| 来源学科分类 | 生态学 |
| 来源机构 | 中国科学院植物研究所 |
| 资源类型 | 学位论文 |
| 条目标识符 | http://119.78.100.177/qdio/handle/2XILL650/287635 |
| 推荐引用方式 GB/T 7714 | 杨帆. 角果碱蓬种子异型性对盐渍化环境的适应意义[D]. 中国科学院大学,2015. |
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