Pollen Housing

What am I looking at?

This is a cross section through a developing floret of a variety of Mexican aster known as Cosmic Orange. The yellow pollen grains (1) are contained within four red pollen chambers (2), or sacs, inside the bilobed anther. You can see the individual cells that make up the anther surrounding the pollen chambers (3). The larger blue cells belong to the lobe, or petal, of a disc floret (4). 

Click on the right arrow to see other views of the pollen and the pollen chambers.

Biology in the background

Asters are often called daisies and are cultivated around the world because of their attractive flowers and scent. The name aster comes from the Greek word asteri, which means “star” – a reference to the fact that the flowers are star-shaped.

They are mainly pollinated by insects and are an important food source for many butterflies. When an insect flies in to feed on the nectar of an aster, it brushes against the flower’s pollen-covered anthers and some of the pollen sticks to the insect. Then the insect flies on to feed at another flower, where some of the pollen stuck to the insect in turn sticks to the stigma of that flower, fertilizing it. While asters are not cultivated for food, they are related to lettuce, chicory, artichokes, and sunflowers.

Asters have medium-sized pollen grains – typically about 35 micrometers across, or roughly half the width of a human hair.

Technique

These images were created using confocal microscopy.