Differential reward in “male” versus “female” pollen of functionally dioecious Solanum
Premise of Study
5-6% of Angiosperm species exhibit a dioecious sexual system, with unisexual “male” or “female” flowers borne on separate plants. The consequent need for inter-individual pollen exchange is a special challenge for taxa where pollen is the sole pollinator reward. Dioecious Australian Solanum assure visits from pollen-foraging bees via production of inaperturate pollen in functionally female (morphologically bisexual) flowers. Biochemical composition of this pollen has not previously been assessed, nor compared to porate pollen from staminate flowers to reveal whether these flowers differ in their pollinator reward potential.
Porate pollen from male flowers and inaperturate pollen from functionally female flowers of two functionally dioecious Australian species were compared for protein and amino acid content. We also assessed pollen from bisexual and staminate flowers of a closely-related andromonoecious species, in which all pollen is porate, as a comparison across co-occurring sexual systems.
In both functionally dioecious species, porate pollen grains from staminate flowers show significantly higher levels of proteins and amino acids than inaperturate pollen grains from functionally female flowers. Levels of proteins and amino acids were highest in bisexual and staminate flowers of the andromonoecious species.
Higher levels of proteins and amino acids in porate pollen of “male” flowers in our functionally dioecious Solanum species suggests a greater level of nutritive reward for bees foraging on “male” plants than those foraging on functionally “female” plants. Greater reward in porate pollen (including andromonoecious species) may be connected to the potential to generate a pollen tube.
American Journal of Botany
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This article has been accepted for publication and undergone full peer review but has not been through the copyediting, typesetting, pagination and proofreading process, which may lead to differences between this version and the Version of Record. Please cite this article as doi: 10.1002/ajb2.1765
Ndem-Galbert, J.R., J. Hall, A.J. McDonnell and C.T. Martine. 2021. Differential reward in “male” versus “female” pollen of functionally dioecious Solanum (Solanaceae). American Journal of Botany. https://doi.org/10.1002/ajb2.1765