Response of Helianthus annuus roots to changes in soil density

Katrina Viegas.  College of St. Benedict, Biology Department, St. Joseph, MN  56374

Roots are a plant’s main method of obtaining nutrients and water from the earth. Therefore, understanding root responses to differences in soil helps explain why some plant species succeed in a given environment while others do not. This knowledge is also practical; in agriculture, for instance, plant varieties with superior root systems can be selectively bred to increase a crop’s resistance to drought (Trump 1977).

The purpose of this project was to measure Helianthus annuus root response to changes in soil density. In order to do so, we planted seeds in media of differing density. We completed three replicates of four treatments each: entirely soft soil material (vermiculite); entirely hard soil material (coarse sand); top layer soft, bottom layer hard; and top layer hard, bottom layer soft. The seedlings were harvested after ten days; the roots were cleaned, digitized, and analyzed for vertical growth, total root length, secondary roots, and root width using Image-J software. In addition, time lapse movies were made of root growth in each type of medium. The results from this experiment will be presented.