Chicory Dickory Dock

What am I looking at?

This is a cross section through a developing floret of a chicory flower (Cichorium intybus). The orange pollen grains (1) are contained within four pollen chambers (2) that are inside each of five anthers. You can see in blue the cell walls (3) of the individual cells that make up the floret. A cross section of the stigma (4) is visible in the center of the image.

Click on the right arrow to see other views of the floret’s pollen and pollen on the stigma.

Biology in the background

Chicory is a flowering plant with bright blue flowers that grows well in temperate and subtropical environments. It’s native to western Asia, North Africa, and Europe and has been introduced to the Americas and Australia. The entire plant is edible and has a mildly bitter to very bitter taste, depending on the species. Common names for cultivated chicory plants include radicchio and endive.

Each star-shaped chicory flower consists of an “eye” surrounded by petals. (Chicories – and asters – are members of the family Asteraceae, which comes from the Greek word asteri, which means “star.”) Each chicory petal is in fact an individual infertile flower – called a “ray flower” – that doesn’t produce pollen or seeds. The “eye” is formed by tiny disc florets; each of these is also an individual flower that contains both pollen-producing reproductive parts (stamens, terminating in anthers) and egg-producing and pollen-receiving parts (pistils, with a stigma at the tip). Five stamens surround each pistil, and this whole radial arrangement is in turn wrapped in a tubular corolla (3) consisting of five fused lobes (the bright blue band in the image). Each pistil carries a bilobed anther with four pollen chambers (2).

The spikes covering the pollen grains help them stick to the legs and bodies of the insects that feed on the flower’s nectar, aiding pollination. Each grain has three apertures – the light blue bumps. Once a pollen grain lands on another floret’s stigma, after being delivered there by an insect, it germinates. One of the apertures sprouts a tubular structure called a pollen tube, which carries the genetic material down the pistil and into the ovules. Once it reaches an ovule, it releases two sperm cells. One of them fertilizes the egg cell, which develops into an embryo.

Chicory flowers have medium-sized pollen grains – typically about 40 micrometers across, or roughly half the width of a human hair.

Technique

These images were created using confocal microscopy.