Knowledge Resource Center for Ecological Environment in Arid Area
| 肉苁蓉结实特性、种子休眠和萌发与环境的关系 | |
| 其他题名 | Seed-setting characteristics, seed dormancy, germination and their relationship with the environment of Cistanche deserticola |
| 王佳 | |
| 出版年 | 2018 |
| 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 | 肉苁蓉（Cistanche deserticola Ma）是列当科多年生草本植物，主要寄生于温带荒漠灌木梭梭（Haloxylon ammodendron（C. A. Mey.）Bunge）和白梭梭（Haloxylon Persicum Bunge ex Boiss. Et Buhse）的根部。肉苁蓉作为一种珍贵中草药，由于过度采挖而成为渐危物种。在自然条件下肉苁蓉种子萌发率极低，严重制约了其人工繁育和资源保护。目前，有关肉苁蓉种子休眠类型、休眠释放和萌发过程中的形态和生理特性变化尚不清楚。因此，本研究以寄生在我国北方干旱荒漠区梭梭上的肉苁蓉为研究对象，通过野外调查、野外控制实验和实验室实验相结合的方法，探讨了（1）肉苁蓉种子的形态结构特征、种子休眠和萌发特性；（2）肉苁蓉结实格局以及结实期干旱对结实特性的影响；（3）肉苁蓉种子形态休眠释放对环境温度的响应；（4）肉苁蓉土壤种子生理休眠的季节性动态。研究将有助于深入了解肉苁蓉从结实、种子休眠释放到种子萌发的生活史关键阶段对荒漠环境的适应性，并为肉苁蓉的人工繁育提供理论基础。主要研究结果如下：1、肉苁蓉具侏儒型种子，其种子存在大小（长度）上的变异。种子大小变异范围为0.2-1.0 mm，其中0.2-0.4 mm为空壳种子，≥ 0.4 mm为可能具生活力的种子。种子重量、胚发育程度、具胚率和生活力随种子长度的增加而升高。新成熟肉苁蓉种子从外部向内部的结构依次为：透水的种皮、气腔、外胚乳、胚乳和未分化的球状胚。新成熟种子在任何设定的变温梯度、光照条件以及萌发刺激物中进行培养均不能萌发。经过冷层积释放生理休眠以及高温释放形态休眠后，种子可在刺激物（氟啶酮）的诱导下萌发。种子萌发前胚需要生长到的关键长度为0.44 mm，相比于新成熟种子，具萌发力的种子胚长度增加了29 %。已萌发的肉苁蓉种子无胚根、胚芽以及子叶结构，只形成类胚根的萌发管结构。肉苁蓉种子具有一种特殊的形态生理休眠，其休眠释放顺序为先生理休眠后形态休眠。这种种子的休眠类型在温带荒漠植物中尚属首次报道。2、肉苁蓉具有单次种子结实量大的繁殖特性。单株肉苁蓉的种子产量约占果序重量的44 %，单株结实种子总数量约为20.1万粒。肉苁蓉结实具有时间和空间上的异质性，肉苁蓉花序从下向上依次开花，果序中的种子从下向上依次成熟。单株肉苁蓉果序由下部向上部，种子趋于变小，空壳种子的数量逐渐增加，具生活力种子的数量逐渐减少，晚期发育的种子空壳率高。种子发育期的干旱改变了单株肉苁蓉果序的结实特性。遮雨处理导致果序下部和中部大种子（0.8-1.0 mm）数量的降低以及果序上部小种子（0.4-0.6 mm）数量的增加。另外，遮雨处理导致果序各部位种子具胚率降低。3、新成熟肉苁蓉种子的形态休眠释放对季节性变温响应不敏感。在模拟原生境季节性变温的以温层积起始（温-冷-温-）和以冷层积起始（冷-温-冷-）的交替层积下培养的肉苁蓉种子，种胚表现出缓慢的生长趋势。当种子分别经过50周的以温层积起始和40周的以冷层积起始的交替层积处理后，种胚长度才发生显著增加。相对于低温下较慢的种胚生长速度，高温（30-40 oC）下种胚的生长速度较快。在35 oC下培养6个月后，种胚即可生长到种子萌发的关键长度（0.44 mm），这一过程的诱发并不依赖于生理休眠的释放。肉苁蓉种子的这种形态休眠释放特性，是温带荒漠植物的一种独特适应机制。4、新成熟肉苁蓉种子具有季节性的生理休眠动态。肉苁蓉种子在成熟时具有初生休眠，散布后种子的生理休眠会在季节性变温的驱动下表现出休眠/状态性休眠之间的动态变化。早秋散布于沙土表面的肉苁蓉种子，在经历冬季低温后种子的生理休眠逐渐释放，种子于次年早春获得较高的萌发潜力（54 %）。次年春季随着温度的升高，种子逐渐丧失萌发潜力，随后于夏季重新获得生理休眠。另外，沙埋深度对肉苁蓉种子生理休眠的季节性动态具有重要影响。随着沙埋深度逐渐增加，种子生理休眠释放对季节性变温的响应程度逐渐降低。与沙土表面的种子相比，沙埋深度为2和5 cm的种子于次年早春分别仅获得20 %和7 %的萌发潜力。综上所述，肉苁蓉通过产生大量侏儒型种子的繁殖特性来提高其后代对恶劣的温带干旱荒漠环境的适合度。肉苁蓉在长期适应温带干旱环境过程中，其种子形成了一种特殊的形态生理休眠，即在形态休眠和生理休眠的季节性释放动态的共同调节下确保种子在环境条件合适且可接触到寄主根系的情况下萌发，通过萌发管寄生到寄主上，是一种“谨慎型”萌发对策。肉苁蓉在结实、种子休眠释放和萌发等生活史关键阶段表现出来的这些生态特性，避免了种子在散布后的大量萌发，使种子以土壤种子库的形式保存在土壤中，这有助于肉苁蓉种群在极端和多变荒漠中生存和繁衍。 |
| 英文摘要 | Cistanche deserticola Ma (Orobanchaceae) is a perennial parasitic herb that mainly parasitizes the root of shrubs Haloxylon ammodendron (C. A. Mey.) Bunge and Haloxylon Persicum Bunge ex Boiss. Et Buhse in the temperate deserts. As a precious medicinal plant, C. deserticola has become endangered due to over collection. Seeds of C. deserticola germinate at a quite low percentage under natural conditions, which has limited the efforts to reproduce artificially from seeds as well as to protect wild resources. Up to now, seed dormancy type and morphological and physiological changes during dormancy release and germination remain unclear. Thus, we collected seeds of C. deserticola that parasitized shrubs of Haloxylon ammodendron (C. A. Mey.) Bunge in an arid desert of northwestern China, and combined methods of field observation, filed control experiment and laboratory experiment were used to study (1) characteristics of seed morphology, seed dormancy and seed germination; (2) seed-setting patterns and effects of drought during seed-development period on seed-setting characteristics; (3) responses of morphological dormancy release to environmental temperature; (4) seasonal dynamics of physiological dormancy in buried seeds. This study will help us fully understand the adaptation of C. deserticola during the critical life history stages from seed-setting, seed dormancy release to seed germination, and provide theoretical basis towards artificial reproduction. The main results are shown as follows:1. C. deserticola produced dwarf seeds, and there existed a variation among seed size (length). The range of seed size varied from 0.2 to 1.0 mm, and seeds with length of 0.2-0.4 mm were empty but those with the length ≥ 0.4 mm might be viable. Seed mass, degree of embryo development, percentages of seeds with viable embryos and seed viability increased with increasing seed length. The structures of fresh seeds of C. deserticola from outside to inside were permeable seed coat, air cavity, perisperm, endosperm and a globular-undifferentiated embryo. Fresh seeds did not germinate during the incubation under any given temperature regimes, light conditions or germination stimulants. Seeds germinated in the presence of stimulant (fluridone) after physiological dormancy was released by cold stratification and morphological dormancy was released by high temperature. Embryo needed to grow to a critical length of 0.44 mm prior to germination, and the length of embryo in germinated seeds had increased by 29 % compared to fresh seeds. A radicular-like germ tube formed instead of radicle, plumule and cotyledons in germinated seeds. Seeds of C. deserticola have a specialized kind of morphophysiological dormancy, and its dormancy release order was physiological dormancy followed by morphological dormancy. This study was the first to report this kind of dormancy in seeds of desert plants in the temperate zone.2. C. deserticola developed reproductive characteristics that had huge seed number within a single reproduction event. The mass proportion of seeds to that of infructescence in a single plant was 44 %, and total seed number of a singe plant was about 0.201 million. Seed-setting patterns in C. deserticola exhibited heterogeneity on the scales of time and space. The inflorescence of C. deserticola bloomed from bottom to top, while seeds matured in the same order. The number of empty seeds increased and seed size as well as the number of viable seeds decreased from bottom to top in infructescences, and seeds produced in the later stage of development had a high proportion of empty seeds. Drought during seed-development period changed seed-setting patterns within a single plant. Rain shelter treatment caused a decrease in bigger seeds (0.8-1.0 mm) in the bottom and middle of infructescence and an increase in smaller seeds (0.4-0.6 mm) in the top of infructescence. Besides, rain shelter treatment caused a decrease in the percentages of seeds with viable embryo in whole infructescence.3. The response of morphological dormancy release to seasonal alternating temperatures was insensitive. The embryo of C. deserticola seeds exhibited slow growth during incubation under warm- (warm-cold-warm-) and cold-started (cold-warm-cold-) alternative stratification that simulated seasonal temperatures in the natural habitat. Embryo length showed a significant increase after seeds were treated with warm-started stratification for 50 weeks and cold-started stratification for 40 weeks. Embryo of seeds showed a faster growth rate under high temperature (30-40 oC) compared to low temperatures. Embryo in seeds grew to the critical length of 0.44 mm after 6 months of moist incubation at 35 oC, and the induction of this process was not dependent on the release of physiological dormancy. The mechanism of morphological dormancy release in the seeds of C. deserticola was a unique adaptive strategy of desert plants in the temperate zone.4. Seeds of C. deserticola exhibited seasonal dynamics of physiological dormancy. Seeds had primary dormancy when they matured, and then the dispersed seeds showed dynamic changes between dormancy and conditional dormancy in physiological dormancy status under the seasonal fluctuating temperatures. Seeds dispersed on surface of sand in early autumn released their physiological dormancy gradually after exposed to low temperature in winter and they gained high germination ability (54 %) in early spring of the next year. Seeds showed a decrease in germination ability with increasing temperature in spring and they re-entered physiological dormancy in later summer. Besides, depths of sand burial had great influence on seasonal dynamics of physiological dormancy. With the increase of sand burial depth, the response of seed morphological dormancy release to seasonal fluctuating temperatures weakened. Compared to seeds on sand surface, seeds buried at 2 and 5 cm only gained 20 % and 7 % germination in spring of the next year.In summary, C. deserticola adopted reproductive characteristics that produced a huge number of dwarf seeds to increase their fitness in the harsh and arid desert environment in the temperate zone. Seeds of C. deserticola had formed a specialized kind of morphophysiological dormancy during the long period of adaptation to arid environment in the temperate zone. That is, seasonal dynamics in morphological and physiological dormancy release was able to ensure the seeds to germinate under suitable environmental conditions when they were exposed to host roots and those seeds parasitized host through germ tube, which was considered as a cautious germination strategy. The ecological traits exhibited during critical history stages of seed-setting, seed dormancy release and germination would avoid the huge germination of dispersed seeds and enable seeds to keep in the soil seed bank, which will benefit the survival and reproduction of C. deserticola populations in the extreme and changing desert. |
| 中文关键词 | 肉苁蓉 ; 形态休眠释放 ; 土壤种子休眠/萌发季节动态 ; 结实特性 ; 形态生理休眠 |
| 英文关键词 | Cistanche deserticola Morphological dormancy release Seasonal dynamics of seed dormancy/germination in soil Seed-setting characteristics Morphophysiological dormancy |
| 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/2XILL650/288213 |
| 推荐引用方式 GB/T 7714 | 王佳. 肉苁蓉结实特性、种子休眠和萌发与环境的关系[D]. 中国科学院大学,2018. |
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