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Floral nectaries and pseudonectaries in Eranthis (Ranunculaceae): petal development, micromorphology, structure and ultrastructure


Flowers are an innovative characteristic of angiosperms, and elaborate petals usually have highly specialized structures to adapt to different living environments and pollinators. Petals of Eranthis have complex bilabiate structures with nectaries and pseudonectaries; however, the diversity of the petal micromorphology and structure is unknown. Petal development, micromorphology, structure and ultrastructure in four Eranthis species were investigated under SEM, TEM and LM. The results show that petals undergo 5 developmental stages, and accessory structure formation (stage 4) mainly determines the diversity of final mature petal morphology and pseudonectaries; the central depression formed in stage 2 will develop into nectary tissues. Petals are bilabiate and have hidden nectaries in nectary grooves; they consist of one layer of rounded and raised secretory epidermal cells and 3–14 layers of secretory cells with abundant plasmodesmata between cells. A large number of sieve tubes are distributed between the cells and extend to the epidermis; in addition, the vessel elements are located below the secretory area. Nectar is stored in the intercellular space between secretory parenchyma cells and escapes through microchannels or cell rupture. Pseudonectaries in all species of Eranthis except for E. hyemalis consist of smooth, ornamented epidermal cells and 9–12 layers of parenchyma cells with sparse cytoplasm, which may have the function of attracting pollinators.

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We thank Da-Lyu Zhong, Meng Han, Shan Su and Wen-Juan Li for sample collection, Siyu Xie for modification of Figure 2, Cheng Xue for comments on an earlier draft of this paper and other staff of Ren’s group for technical assistance. We sincerely thank two anonymous reviewers for providing valuable comments and suggestions.


This work was supported by the National Natural Science Foundation of China (No. 31770203, 31100141) and the Fundamental Research Funds for the Central Universities (No. GK201603067, No. GK202002011 and 2452017155).

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Correspondence to Xiaohui Zhang.

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Huang, Z., Zhang, X. Floral nectaries and pseudonectaries in Eranthis (Ranunculaceae): petal development, micromorphology, structure and ultrastructure. Protoplasma 259, 1283–1300 (2022).

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