Inverse Relationship Between Stomatal Density and Nitrogen Level in Salmonberry (Rubus Spectabilis)

Abstract

The importance of salmon to riparian communities has been studied in-depth. One study revealed a positive correlation between the density of spawning salmon and stomatal density of Salmonberry (Rubus Spectabilis) growing nearby. An explanation for this relationship could be that when nutrients, including nitrogen, are added to the environment by decomposing salmon, plants are no longer limited by nutrient availability, but instead are limited by CO₂ intake. As a result, plants may increase stomatal density of new leaves to increase CO₂ intake, which would result in increased photosynthesis and plant growth. To test this, we grew Salmonberry in low and high nitrogen level solutions. We measured plant growth as stem length, leaf width, and leaf length, and we measured the stomatal density of new leaves. Our results showed that measurements of growth increased significantly at high nitrogen levels. However, we also found that stomatal density was significantly decreased at high nitrogen levels, the opposite of what we predicted. The reason for this relationship is not clear, but it could be due to a difference in leaf sizes between the two treatment groups. Smaller leaves could have smaller cell sizes, resulting in more stomata per unit area than larger leaves, even if the leaves have the same total number of stomata. Overall, the inverse relationship we found between stomatal density and nitrogen level may indicate a different relationship than previous studies have found, but further studies need to be done that also consider leaf size before we can make this conclusion.