Corn germination

This short movie shows corn seeds germinating and growing in darkness over a period of a few days starting 36 hours after being planted in wet soil. Note that the root is the first part of the seedling to emerge from the seed. The seed on the left was planted with the embryo aligned with its root pointing down. The seed on the right was oriented with the embryo upside down. As the movie shows, the roots from both seeds grew down regardless of the initial orientation of the embryo. Also, the shoots that emerged later grew up from both seeds. The ability of the seedling to orient its growth occurs as a result of the process of gravitropism. Gravitropism is the process by which plants sense and respond to the direction of gravity. The time between images in this movie was 1 hour.

In darkness, as would occur for seeds buried in soil, most of the food reserves in the seed are used to provide resources for the seedling to grow enough to reach the light and produce its own food by photosynthesis. Through gravitropism, the seedlings can send their shoot towards the surface of the soil where it will eventually emerge into light. At the same time. the seedling uses gravity to orient its roots so they grow down into the soil where they can find water and minerals for growth. Movies showing more about gravitropism can be found in the main menu selection "Gravitropism". This dark growth is called etiolation. Once the shoot is exposed to light, the plants undergo a process called photomorphogenesis, during which leaves develop and become green. Movies showing the process of photomorphogenesis can be found in the main menu selection "Effect of light".