Zingiber densissimum flower, pollen and pollinators.

(A): The floral stucture of Zingiber densissimum: TA, tail-like anther crest; S, stigma; A: anther; L: labellum staminode. (B): A fresh flower with the anther appendage manually pushed up to show the secondary pollen presentation mechanism: PA, pollen on the anther; PL, pollen on the labellum staminode; the arrow shows the aggregated pollen chains. (C)-(F): pollen conditions under different treatments, images are to the same scale. (C): Pollen grains that were fixed in FAA solution and observed under a light microscope after stained with aniline blue, with all layers of pollen wall sticking together. (D): A pollen grain observed under a light microscope after water swelling, with all three layers of pollen wall separated. (E): A pollen grain stained with aniline blue and observed under a light microscope after water swelling. (F): The same pollen grain as (E) observed under a fluorescence microscope, with only the layer III reflecting fluorescence. (G): A flower dorsally pollinated by a bee of Macropis hedini. (H): A flower ventrally pollinated by a bee of Amegilla zonata, with a leg of the bee touching the stigma.