Bucknell University, Biology Department, 1 Dent Drive, Lewisburg, PA, 17837, USA.
ETH Zurich, Department of Health Sciences and Technology, Vladimr-Prelog route 1-5/10, 8093 Zurich, Switzerland.
Am J Bot. 2021 Nov;108(11):2282-2293. doi: 10.1002/ajb2.1765. Epub 2021 Nov 20.
Five to six percent 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 pollen from Australian Solanum has not 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 had 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 nutritive reward for bees foraging on "male" plants than for 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.
有 5%至 6%的被子植物物种表现出雌雄异株的性系统，其单性“雄性”或“雌性”花分别着生于不同的植株上。因此，对于那些花粉是唯一传粉报酬的类群来说，个体间花粉交换是一个特殊的挑战。澳大利亚茄属的雌雄异株植物通过在功能上为两性花的雌性花中产生无孔花粉来确保有访花的传粉蜜蜂。尚未评估澳大利亚茄属植物的花粉生化组成，也未与来自雄花的有孔花粉进行比较，以揭示这些花在其传粉报酬潜力方面是否存在差异。
对来自两性花的有孔花粉和来自功能上为两性花的无孔花粉的两种功能上雌雄异株的澳大利亚物种的蛋白质和氨基酸含量进行了比较。我们还评估了与其同域分布的雌雄同体物种的两性花和雄花的花粉，作为在共存的性系统中进行比较。
在这两个功能上的雌雄异株物种中，来自雄花的有孔花粉粒的蛋白质和氨基酸含量明显高于来自功能上为雌性花的无孔花粉粒。在雌雄同体和雄花的两性同体物种中，蛋白质和氨基酸的含量最高。
在我们功能上的雌雄异株茄属植物中，来自“雄性”花的有孔花粉粒中蛋白质和氨基酸的含量较高，这表明在“雄性”植物上觅食的蜜蜂获得的营养报酬比在功能上为“雌性”植物上觅食的蜜蜂更高。有孔花粉（包括雌雄同体物种）中的更高报酬可能与产生花粉管的潜力有关。
