470— Quantifying the Shape of a Plant (Brassica rapa) During Growth Under Different Light Intensities Using Fractal Geometry

Over time plants not only increase in size but also change their shape. Quantifying this change in shape, however, is challenging. Fractal dimension, a measure of how these plants fill space, can provide a wholistic understanding of plant shape and how that shape changes as the plants react to their environments. I used a high-resolution, three-dimensional scanner to estimate the shape of Brassica rapa plants during growth under three different light intensities: low (40 Einsteins), medium (75 Einsteins) and high (100 Einsteins). From these data, each plant's above-ground shape was quantified using fractal geometry. The fractal dimension (D) of plants grown under the low and medium light conditions increased asymptotically with growth rates 0.13769 and 0.16009, respectively, to fractal dimension 1.660 and 1.640, respectively. Plants grown under high light had a mean constant fractal dimension of 1.524 over the course of the experiment. I developed a 3-dimensional diffusion-limited aggregation model of plant growth over time which accounts for light intensity in order to test whether this simple set of rules can simulate plants with a similar shape. Results suggest that the model is capable of generating plants with a fractal dimension growth curve comparable to that of experimentally grown plants.