Germen Germination

What am I looking at?

This image shows a thale-cress sprout, in light blue (1), emerging from its seed casing, in brown (2). The “tail” (3) will be the root system of the plant and the top, still partially covered by the seed casing (4), will be the plant’s first two leaves.

Click on the right arrow to see an image that depicts several different stages of the seedling emerging from its seed casing.

Biology in the background

Most plant seeds need a few things to let them know it is time to sprout. First, they need moisture. Seeds will not sprout in dry conditions because the young plant will need water to grow and stay healthy, though the seed itself can generally stay dormant, but alive, for a long time in dry conditions. Second, seeds need the right temperature. Young plants are particularly vulnerable to extreme temperatures, so seeds don’t tend to sprout until there have been a few days in a row in the ideal temperature range. Finally, plants and their seeds have to “breathe,” so they need to have access to air for the sprouting process to begin.

A thale-cress seed is about 600 micrometers across, or roughly eight times bigger than the width of a human hair. The seedlings that emerge from the seed are about twice that size.

Technique

These images were created using focus-stacked widefield autofluorescence microscopy under UV excitation light.