Seed characterization and germination morpho-physiology of Simira gardneriana (Rubiaceae)

Abstract: Simira gardneriana (Rubiaceae) is a newly discovered tree species endemic to the Caatinga. For this reason, studies aimed at propagation, seed and seedlings analysis are essential for morphology, identification, classification, and conservation. Our objective was to characterize the seeds, the morpho-physiology of germination and seedling establishment of S. gardneriana. Therefore, we performed physical, biometric, biochemical, and morphological characterization of the seeds, as well as an evaluation of the germination process and seedling establishment. Hydration of seeds was carried out by three methods (immersion in water, on a wire mesh, and between paper rolls) and at two temperatures (25 and 30 °C). Morphological characterization of the seedlings was performed on paper substrate at 30 °C for 28 days. Seeds of S. gardneriana are orthodox, amylo-lipid, have an endosperm and do not exhibit physical dormancy. Hydration and germination of the seeds can be achieved in a paper roll at 30 °C with root protrusion on the sixth day, and complete seedling formation on the 28th day after sowing. Seedlings of S. gardneriana are phanero-epigeal cotyledonous with photosynthetic cotyledons and have ability to regrow the root system. Characterization of S. gardneriana seeds, germination and seedlings contributes to its propagation and may help in subsequent taxonomic and phylogenetic studies in Rubiaceae.

摘要：加德纳西米拉（Simira gardneriana，茜草科（Rubiaceae））是新发现的仅分布于卡廷加（Caatinga）植被区的乔木物种。有鉴于此，针对该物种的繁殖、种子与幼苗开展相关研究，对其形态学研究、物种鉴定、分类及保护工作而言至关重要。本研究旨在对加德纳西米拉的种子、种子萌发形态生理学以及幼苗建成过程进行表征。为此，我们对该物种的种子开展了物理、形态计量、生化及形态学表征，并对其萌发过程与幼苗建成情况进行了评估。种子吸胀处理采用三种方式：水中浸泡、金属网支撑培养以及纸卷培养，并设置25℃与30℃两个温度梯度。幼苗形态学表征在30℃的纸基基质上开展，培养周期为28天。该物种种子属于正统种子（orthodox seed），兼具淀粉与脂类储藏物质，具有胚乳（endosperm），且未表现出物理休眠（physical dormancy）特性。在30℃的纸卷培养条件下即可实现种子吸胀与萌发：播种后第6天即可观察到胚根突破种皮，第28天完成幼苗建成。加德纳西米拉的幼苗为显生出土型子叶幼苗（phanero-epigeal cotyledonous），其子叶具备光合能力，且根系具有再生能力。对加德纳西米拉的种子、萌发过程及幼苗的相关表征研究，可为该物种的繁殖工作提供支撑，同时可为茜草科（Rubiaceae）后续的分类学与系统发育研究提供参考依据。