Knowledge Resource Center for Ecological Environment in Arid Area
| 毛乌素沙地两种固沙禾草种子萌发和幼苗生长与环境的关系 | |
| 其他题名 | Seed Germination and Seedling Growth in Two Sand-binding Grasses in Mu-Us Sandland |
| 朱雅娟 | |
| 出版年 | 2007 |
| 学位类型 | 博士 |
| 导师 | 董鸣 |
| 学位授予单位 | 中国科学院植物研究所 |
| 中文摘要 | 干旱区和半干旱区生长的植物具有复杂的生存机制，以确保其能够在特定的环境中生存和发展。植物在干旱的荒漠条件下的生存，与其特殊的种子萌发机制密切相关，这种机制能够确保植物在合适的时间与地点进行种子萌发与幼苗生长发育。在植物的生活史中，种子对极端环境具有最大的忍耐力，而萌发的幼苗对环境胁迫的忍耐程度最小。在干旱区生长的植物往往具有特殊的萌发机制使萌发出的幼苗能够度过对外界的敏感期，对于植物的生存具有重要意义。\n 毛乌素沙地是我国的四大沙地之一，该地区具有水分短缺，蒸发强烈，风沙剧烈和生境异质性高的特征。本文假设生长在这种极端环境中的植物也发展出了“适时适地”的种子萌发和幼苗生长的适应对策。为了验证以上的假设，本文选取毛乌素沙地不同生境中生长的两种优势固沙禾草——流动沙丘上生长的沙鞭(Psammochloa villosa)和固定沙丘上生长的赖草(Leymus secalinus)为研究材料，通过野外调查、温室控制实验和实验室控制实验的方法，从生理生态学的角度探讨这两种植物的种子萌发和幼苗生长过程对沙丘环境的适应对策，主要对比它们在种子休眠、萌发和幼苗早期生长过程中对沙丘生境适应性的异同点。研究结果表明：\n （1）新成熟的沙鞭和赖草的种子为适应冬季低温而发展出生理性的内生休眠——非深度生理休眠。沙鞭和赖草的种子分别需要经过4周和8周的低温层积处理(3－5ºC)来完全打破休眠。另外，划破种皮或者部分切除胚乳也能够促进种子的萌发，这进一步证明两种植物的种子具有非深度生理休眠。然而，切除胚乳在不同程度上影响它们的幼苗生长。由非深度生理休眠、温度和损伤种皮/胚乳调节的部分萌发机制能够确保两种植物的种子即使在条件适宜的情况下只有部分种子萌发，从而分散植物生存的风险性。\n （2）毛乌素沙地的小量降水（无法触发萌发）使种子经常遭受湿润－干燥的交替胁迫过程。种子先在湿润条件下吸涨1d或者2d，然后在室温下干燥0-8天。尽管在经历反复吸涨和自然干燥脱水后仍能够保持萌发能力，沙鞭和赖草种子的萌发特性却发生了不同的变化：和各自的对照相比，沙鞭种子萌发率相同而萌发速率降低；赖草种子的萌发率和萌发速率都降低，部分种子进入休眠状态。沙鞭和赖草萌发出的幼苗可能由于没有后续降雨或者因沙蚀而遭受干燥胁迫，但是其幼苗在生长早期能够忍耐一定程度的干燥，再次湿润后部分幼苗能够恢复生长。沙鞭和赖草幼苗的耐干燥的“极限点”不同：当幼根长度为1 mm时，它们的幼苗忍耐干燥的时间分别是60d和30d；当幼根长度为4 mm时，它们的幼苗忍耐干燥的时间分别是14d和7d。沙鞭和赖草的种子和生长早期的幼苗的耐干燥性特性可能是它们对降雨量和降雨时间都不可预测的沙地生境的生存策略之一。\n （3）不同的沙埋深度影响沙鞭和赖草的种子萌发和出苗。这两种植物的种子萌发和出苗都需1－2 cm的浅层沙埋。随着沙埋深度的增加，两种植物的种子萌发率和出苗率逐渐降低，强迫休眠率逐渐升高；萌发率与出苗率和沙埋深度呈负相关关系而休眠率和沙埋深度呈正相关关系。但是，沙鞭种子出苗的最大沙埋深度是8 cm，而赖草的则为4 cm。因强迫休眠而没有萌发的种子对维持一个长期的土壤种子库来说具有生态学优势，这些种子暴露在合适的萌发土壤深度时具有生长出幼苗的潜能。\n （4）沙鞭和赖草的种子都具有大小的差异性，种子大小对沙鞭和赖草的种子在不同沙埋深度的出苗具有不同的影响。沙鞭的三种不同大小种子的平均质量分别为小，4.489 ± 0.012 mg (4 – 4.9 mg)；中，5.457 ± 0.012 mg (5 – 5.9 mg)和大，6.415 ± 0.011 mg (6 – 6.9 mg)。赖草的两种不同大小种子的平均质量分别为小，3.083 ± 0.026 mg (3 – 3.5 mg)和大3.955 ± 0.028 mg (3.6 – 4.0 mg)。在相同的沙埋深度下，两种植物的大种子的出苗率都显著高于小种子。和小种子相比，两种植物的大种子由于贮藏更多的能量，所以在相同深度的沙埋中具有出苗率更高的生态优势，而大量小种子在沙埋中不能萌发，可以作为种子库保存在沙层中，这样就分散了一次性大量萌发给植物带来的冒险性。\n （5）沙鞭和赖草的幼苗在生长过程中会遭受沙埋，其幼苗忍耐沙埋的能力与沙埋的相对深度（沙埋比例）和幼苗年龄有关。沙鞭和赖草幼苗的耐沙埋能力不同：沙鞭的2周龄幼苗可以忍耐达到株高100%的沙埋，而其1周龄幼苗只能忍耐75%的沙埋。赖草的1周龄和2周龄幼苗都只能忍耐75%的沙埋。沙埋之后，沙鞭和赖草幼苗的生物量，根/茎比以及根和茎的长度都受到不同程度的影响。赖草幼苗不能忍耐完全沙埋可能是限制它在流动沙丘上分布的一个原因。\n （6）降雨量和降雨频率能够不同程度地影响沙鞭和赖草在不同沙层的萌发和出苗。这两种植物的种子萌发和出苗需要的最小降雨量不同：在一次浇水相当于5 mm降雨量后，沙鞭和赖草种子的萌发率都超过50%；但是使沙鞭和赖草的出苗率能够达到50%的降雨量分别为10 mm和15 mm。沙埋中的沙鞭和赖草种子的出苗对降雨的响应具有以下特征：两种植物种子的出苗随降雨量或者降雨频率的增加而增加；沙鞭的出苗率受到降雨量和降雨频率的显著影响，但是二者交互作用的影响不显著；赖草的出苗率受到降雨量、降雨频率以及二者交互作用的显著影响。\n 根据沙鞭和赖草在沙丘上的种子萌发和幼苗生长特性，本文为毛乌素沙地通过植物固沙恢复受损的沙地生态系统的种子飞播实践提出了几点建议。 |
| 英文摘要 | In arid and semiarid zones, plant species possess complex strategies to ensure their survival and development in these specific environments. The survival of plants in desert is connected closely with the special seed germination strategy which ensures seed germination and seedling development at the right time and in the right place. During the life cycle of a plant species, seed has the highest resistance to the extreme environmental factors, whereas seedling has the lowest. Plant species in arid zones often has specific germination strategies to enable seedling live through the sensitive stage and this is important to plant survival.\n Mu-Us Sandland is one of the four mainly Sandland in China. The environment characters are water shortage, high evaporation, sand burial and habitat heterogeneity. The study discussed seed dormancy, seed germination and seedling growth of two sand-binding grasses in different habitat in Mu-Us Sandland: Psammochloa villosa inhabits on mobile sand dunes, and Leymus secalinus distributes on fixed sand dunes. The purpose of this study was to compare the adaptation of seed germination and seedling growth to sand dune habitat in the two grasses. \n The results showed: (1) freshly matured seeds of P. villosa and L. secalinus are in non-deep physiological dormancy to adapt to the cold winter. Seed dormancy of P. villosa and L. secalinus could be completely broken by 4 or 8 weeks of cold stratification (3-5 ºC). In addition, germination percentage was increased by scarifying the caryopsis coat or by artificial removal of partial endosperm. However, seedling development was influenced by endosperm removal. The partial germination strategy regulated by physiological dormancy, temperature and seed damage ensures only a few seeds germinated in suitable conditions and thus spread the risk of plant survival.\n (2) Seeds of P. villosa and L. secalinus often suffered from the stress of wet-dry cycle caused by few precipitations (unable to induce seed germination) in Mu-Us Sandland. Seeds were imbibition for 1 or 2 days and then were dried in room temperatures for 0-8 days. Although seeds kept germination ability after imbibition and dehydration, there were different changes in their germination characters. Compare to their control, seed germination percentage of P. villosa was same whereas its germination rate decreased after wet-dry; however, the percentage and rate of seed germination of L. secalinus decreased by wet-dry, and some seeds became in dormant. Their seedlings in early growth stage could resist to desiccation and recover to growth after rehydration. However, “the point of no return” of desiccation tolerance was different in P. villosa and L. secalinus. When root length was 1 mm, seedlings of P. villosa and L. secalinus could endure 60 days or 30 days desiccation, respectively. Desiccation tolerance of seeds and early growth seedlings of two grasses might be one of the survival strategies in sandland with unpredictable precipitation.\n (3) Different sand burial depth affected seed germination and seedling emergence of P. villosa and L. secalinus. 1-2 cm sand burial was necessary for seed germination and seedling emergence of two grasses. As sand burial depth increased, their seed germination and seedling emergence decreased and enforced dormancy increased. The maximal seedling emergence depth of P. villosa and L. secalinus was 8 cm and 4 cm, respectively. The seeds in enforced dormancy could maintain a long time soil seed bank and could produce seedlings after exposure to suitable sand depth.\n (4) There was diversity in seed size of P. villosa and L. secalinus. The mean mass of three different size of P. villosa seeds were: small, 4.489 ± 0.012 mg (4 – 4.9 mg); medium, 5.457 ± 0.012 mg (5 – 5.9 mg); and large, 6.415 ± 0.011 mg (6 – 6.9 mg). The mean mass of two different size of L. secalinus seeds were: small, 3.083 ± 0.026 mg (3 – 3.5 mg) and large, 3.955 ± 0.028 mg (3.6 – 4.0 mg). Seed size had different effect on seed germination and seedling emergence at different sand burial depth. At the same sand burial depth, seedling emergence from large seeds of two grasses was higher than small seeds. Large seeds of P. villosa and L. secalinus stored more energy and had more ecological advantage (higher seedling emergence). However, a lot of small seeds did not germinate after sand burial and could keep in soil seed bank, and thus spread the risk of massive germination.\n (5) Seedlings growth of P. villosa and L. secalinus might suffer from sand burial. The endurance of their seedlings to sand burial was related to the relative sand burial depth and seedling age. Seedling endurance to sand burial was different in P. villosa and L. secalinus. Two-week old seedlings of P. villosa could endure total sand burial (100% shoot height) and its one-week old seedlings only endure 75% sand burial. Both of the one-week and two-week old seedlings of L. secalinus only resist to 75% sand burial. The biomass, shoot length, root length and root/shoot ratio of two grasses was affected by sand burial. The distribution of plant species on sand dunes might be restricted by their seedling endurance to total sand burial.\n (6) Precipitation and its frequency affected seed germination and seedling emergence of P. villosa and L. secalinus at different sand burial depth. More than 50% seeds to two grasses germinated after once 5 mm precipitation; and more than 50% seedlings of P. villosa and L. secalinus emerged after once 10 mm or 15 mm precipitation. The characteristic in seedling emergence of P. villosa and L. secalinus responed to precipitation were: seedling emergence of two grasses increased with the increase of precipitation or its frequency; seedling emergence of P. villosa was affected significantly by precipitation and its frequency, but their interactions was not significant; and seedling emergence of L. secalinus was affected significantly by precipitation, frequency and their interactions.\n Based on the seed germination characteristics on sand dunes of these two species, the rational aerial seedling practice were suggested in the processes of ecological restoration in Mu-Us Sandland. |
| 中文关键词 | 低温层积处理 ; 耐干燥性 ; 毛乌素沙地 ; 降雨 ; 沙埋 ; 种子休眠 ; 种子萌发 ; 幼苗生长 |
| 英文关键词 | Cold stratification Desiccation tolerance Mu-Us Sandland Precipitation Sand burial Seed dormancy See |
| 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/2XILL650/286610 |
| 推荐引用方式 GB/T 7714 | 朱雅娟. 毛乌素沙地两种固沙禾草种子萌发和幼苗生长与环境的关系[D]. 中国科学院植物研究所,2007. |
| 条目包含的文件 | 条目无相关文件。 | |||||
| 个性服务 |
| 推荐该条目 |
| 保存到收藏夹 |
| 导出为Endnote文件 |
| 谷歌学术 |
| 谷歌学术中相似的文章 |
| [朱雅娟]的文章 |
| 百度学术 |
| 百度学术中相似的文章 |
| [朱雅娟]的文章 |
| 必应学术 |
| 必应学术中相似的文章 |
| [朱雅娟]的文章 |
| 相关权益政策 |
| 暂无数据 |
| 收藏/分享 |
除非特别说明，本系统中所有内容都受版权保护，并保留所有权利。
