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Structure of floral nectaries and female-biased nectar production in protandrous species Geranium macrorrhizum and Geranium phaeum

  • Agata Konarska
  • Marzena MasierowskaEmail author
Original Article


Nectar is a major floral reward offered to pollinators by plants. In dichogamous plant species, differences in nectar production across sexual phases often occur, but both the male- and female-phase flowers have to attract pollinators to achieve effective pollination. Nectar-producing structures, i.e. floral nectaries, are a key component of floral organisation and architecture, and the knowledge of their structure and function contributes to better understanding of the plant–pollinator interactions. In the present study, we investigated the morphology and structure of nectaries and the nectar production pattern in two protandrous species Geranium macrorrhizum and G. phaeum. The flowers of the studied species have been shown to exhibit varied availability of nectar for insect visitors. Their nectaries differ in the shape, size and thickness. The other differences include the localisation of the stomatal field, the size and number of nectarostomata, the presence of non-glandular and glandular trichomes, the presence of tannin idioblasts, the mode of secretion and the occurrence of plastids functioning probably as autophagosomes and autolysosomes, whose presence in nectary cells has been described for the first time. The flowers of the studied species started nectar secretion in the non-receptive phase before pollen presentation and nectar was produced throughout both sexual phases. The nectar production was gender biased towards the female phase in the nectar amount, nectar sugar concentration and total sugar secreted in the nectar. We postulate that the nectar production patterns in G. phaeum and G. macrorrhizum might have evolved as a response to pollinators’ pressure.


Flower organisation Nectary anatomy and ultrastructure Nectar secretion and transport Autophagosome plastids Female-biased nectar production 



We are greatly indebted to Magda Kamińska PhD for her skilled technical assistance. Transmission electron microscopy studies were performed at the Laboratory of Electron Microscopy, Nencki Institute of Experimental Biology, Warsaw, Poland.

Funding information

This research was supported financially by the Ministry of Science and Higher Education of Poland as part of the statutory activities (projects OKB/DS/8 and OKB/DS/1) of the Department of Botany, University of Life Sciences in Lublin.

Compliance with ethical standards

Conflict of interest

The authors declare that they have no conflict of interest.

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© Springer-Verlag GmbH Austria, part of Springer Nature 2019

Authors and Affiliations

  1. 1.Department of Botany and Plant PhysiologyUniversity of Life Sciences in LublinLublinPoland

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