Petals are important floral organs that exhibit considerable morphological diversity in terms of colour, shape, and size. The varied morphologies of mature petals can be linked to developmental differences. The petals of Berberidaceae (a core group of Ranunculales) range from flat sheets to complex structures with nectaries, but studies on petal development and structural diversity in this group are lacking. Here, the petal development, structure, and micromorphology of seven Berberidaceae genera are characterized by microscopy to clarify the diversity of petals within this group. The results indicate that no common petal-stamen primordium exists, that petal development proceeds through five stages, and that the differentiation responsible for the diversity of the mature petals occurs during stage 4. Processes contributing to the morphological diversity of mature petals include edge thickening, gland formation, and spur formation. Nandina and Diphylleia lack nectaries. Gymnospermium has saccate nectaries, Caulophyllum has nectaries on the petal margin, Epimedium has spur nectaries, and Berberis and Mahonia have glands at the base of petals. Petal nectaries usually consist of a secretory epidermis, two to twenty layers of secretory parenchyma cells, and vascular tissues. Eleven distinct cell types were observed in the petal epidermis, three of which are secretory; papillose cells appear to be absent in Diphylleia, which shows relatively little micromorphological variation. The ancestors of Berberidaceae may have nectaries in thickened areas of their petals. The micromorphology and nectary structures of the petals in Ranunculales are also compared.

中文翻译：

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小檗科花瓣的多样性：花蜜腺的发育、微形态和结构

花瓣是重要的花器官，在颜色、形状和大小方面表现出相当大的形态多样性。成熟花瓣的不同形态可能与发育差异有关。小檗科（毛茛科的一个核心群）的花瓣范围从扁平片到带有蜜腺的复杂结构，但缺乏对该群花瓣发育和结构多样性的研究。在这里，七个小檗科属的花瓣发育、结构和微形态学通过显微镜进行表征，以阐明该组内花瓣的多样性。结果表明，不存在共同的花瓣-雄蕊原基，花瓣发育经历了五个阶段，成熟花瓣多样性的分化发生在第4阶段。促成成熟花瓣形态多样性的过程包括边缘增厚、腺体形成和骨刺形成。Nandina 和 Diphylleia 没有蜜腺。Gymnospermium 有囊状蜜腺，Caulophyllum 在花瓣边缘有蜜腺，淫羊藿有刺状蜜腺，Berberis 和 Mahonia 在花瓣基部有腺体。花瓣蜜腺通常由分泌表皮、二至二十层分泌薄壁细胞和维管组织组成。在花瓣表皮中观察到 11 种不同的细胞类型，其中三种是分泌型的；Diphylleia 中似乎不存在乳头状细胞，其微形态变化相对较小。小檗科的祖先可能在花瓣的增厚区域有蜜腺。