What’s the Rush

What am I looking at?

This is a fluorescently labeled cross-section through the leaf of a rush plant. The red portion around the exterior represents the cells exposed to the environment (1). These cells contain chloroplasts. Chloroplasts contain a green pigment called chlorophyll that appears red under the laser of a microscope. Since these plants are semiaquatic, the exterior cells could be exposed to either water or air. Most of the inside of the leaf is made up of a blue lattice of star-shaped cells (2) that transport air to submerged parts of the plant. The light blue/orange nodes at the junctions of exterior and interior cells (3) are where water and nutrients are transported through the leaf.

Click the right arrow to see additional cross sections of rush leaves at different levels of magnification.

Biology in the background

Plants need both air and water to survive. Water is absorbed through the roots and distributed throughout the plant via its vascular system (3). In plants that grow near or in water, the leaves and stems have a unique structure (2) that allows air to enter and be transported to the submerged parts of the plant via holes in its spongy interior.

In the past, this structure made rush plants useful in the home. Rushlights were used as candles for centuries; the pith of the rush was removed and dipped in animal fat or beeswax to create a candle.

The leaf of a rush plant can grow up to 30 centimeters long (about a foot).

Technique

This image was created using confocal microscopy.