Physiological, physical, and morpho-anatomical changes in Libidibia ferrea ((Mart. ex Tul.) L.P. Queiroz) seeds after overcoming dormancy

Seed dormancy is a phenomenon that affects the distribution of plant species in time. However, it may slow germination and consequently hinder seedling production in nurseries. Many seeds of forest species of the Fabaceae family, such as Libidibia ferrea (Brazilian ironwood), have physical dormancy caused by impermeability of the seed coat to water. Therefore, the aim of this study was to evaluate the physiological, physical, and morpho-anatomical characteristics of L. ferrea seeds before and after application of different treatments for overcoming dormancy. We evaluated the imbibition curves, germination percentage, germination speed index (GSI), the force required to puncture the micropylar region, and morpho-anatomical changes through images obtained from a scanning electron microscope (SEM) before and after application of treatments for overcoming dormancy. L. ferrea seeds immersed in sulfuric acid show a triphasic pattern of imbibition. The required force to puncture the micropylar region of L. ferrea seeds is less for both the treatment with boiling water and for treatments with sulfuric acid. In addition, the required force to puncture the micropylar region decreases during imbibition of the seeds after application of sulfuric acid. The time of application of sulfuric acid influences the thickness of the material removed from the macrosclereid layer of the seed coat.

种子休眠是一种影响植物物种时间分布的现象，但其可延缓种子萌发，进而阻碍苗圃的种苗生产。诸多豆科（Fabaceae）林木树种的种子，如孪叶豆（Libidibia ferrea，俗称巴西铁木），均存在由种皮不透水性引发的物理休眠。为此，本研究旨在评估孪叶豆种子在施加不同破除休眠处理前后的生理、物理及形态解剖学特征。研究中，我们通过扫描电子显微镜（SEM）获取的图像，对孪叶豆种子在破除休眠处理前后的吸胀曲线、发芽率、发芽速度指数（GSI）、珠孔区域穿刺所需力，以及形态解剖学变化进行了测评。经硫酸浸泡处理的孪叶豆种子，其吸胀过程呈现三相模式。沸水浸泡与硫酸处理两种方式下，孪叶豆种子珠孔区域的穿刺所需力均更低。此外，经硫酸处理后的种子在吸胀过程中，其珠孔区域穿刺所需力会逐步降低。硫酸处理时长会影响种皮栅状石细胞层（macrosclereid layer）被去除的材料厚度。