Fruit and seed heteromorphism in the cold desert annual ephemeral Diptychocarpus strictus (Brassicaceae) and possible adaptive significance
Fruit and seed heteromorphism in the cold desert annual ephemeral Diptychocarpus strictus (Brassicaceae) and possible adaptive significance
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DOI：
10.1093/aob/mcq041
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发表时间：
2010-06-01
期刊：
影响因子：
4.2
通讯作者：
Baskin, Carol C.
中科院分区：
文献类型：
--
作者：
Lu, Juanjuan;Tan, Dunyan;Baskin, Carol C.
中国西北寒冷沙漠中的一种一年生植物，其果实和种子都是异型的。本研究的主要目的是表征该物种果实和种子的形态和解剖特征，并比较果实和种子的异型性在传播和萌发中的作用。测定了硅橡胶和种子的形状、大小、质量、分布以及种子黏液层的厚度，并采用标准方法研究了硅橡胶和种子的解剖结构、种子黏液对种子吸水脱水、萌发和附着土壤颗粒的作用、下硅橡胶果皮对种子休眠、成熟后和萌发物候的作用。植物产生开裂的上果皮，薄果皮含有种子，有大的翅膀和厚的粘液层；不开裂的下果皮，厚果皮含有几乎无翅膀的种子，薄的粘液层。上角果种子的传播能力比完整的下角果种子的传播能力大得多。黏液增加了种子吸水量，降低了脱水速率。黏液层较厚的种子比黏液层较薄或已去除黏液的种子对土壤颗粒的粘附性好得多。新鲜种子在夏季处于生理休眠和后成熟状态。非休眠种子在光照和黑暗条件下的发芽率都很高。由于夏季和秋季的干旱，上部角果的种子延迟到春季萌发，而下部角果中厚而不裂的果皮则阻碍了种子萌发。狭叶橐吾的生命周期在时间和空间上通过与果实和种子异型性相关的性状组合在形态和生理上适应了寒冷的沙漠环境。
Diptychocarpus strictus is an annual ephemeral in the cold desert of northwest China that produces heteromorphic fruits and seeds. The primary aims of this study were to characterize the morphology and anatomy of fruits and seeds of this species and compare the role of fruit and seed hetermorphism in dispersal and germination.Shape, size, mass and dispersal of siliques and seeds and the thickness of the mucilage layer on seeds were measured, and the anatomy of siliques and seeds, the role of seed mucilage in water absorption/dehydration, germination and adherence of seeds to soil particles, the role of pericarp of lower siliques in seed dormancy and seed after-ripening and germination phenology were studied using standard procedures.Plants produce dehiscent upper siliques with a thin pericarp containing seeds with large wings and a thick mucilage layer and indehiscent lower siliques with a thick pericarp containing nearly wingless seeds with a thin mucilage layer. The dispersal ability of seeds from the upper siliques was much greater than that of intact lower siliques. Mucilage increased the amount of water absorbed by seeds and decreased the rate of dehydration. Seeds with a thick mucilage layer adhered to soil particles much better than those with a thin mucilage layer or those from which mucilage had been removed. Fresh seeds were physiologically dormant and after-ripened during summer. Non-dormant seeds germinated to high percentages in light and in darkness. Germination of seeds from upper siliques is delayed until spring primarily by drought in summer and autumn, whereas the thick, indehiscent pericarp prevents germination for > 1 year of seeds retained in lower siliques.The life cycle of D. strictus is morphologically and physiologically adapted to the cold desert environment in time and space via a combination of characters associated with fruit and seed heteromorphism.