Author(s): Xander Hulse, Laine Smith
Mentor(s): Michael Stevens
Institution UVU
Clay phacelia (Phacelia argillacea) is an endangered plant that grows only on steep shaley slopes of the Green River Formation in two natural populations in Spanish Fork Canyon, Utah. We collected seeds from ten wild clay phacelia plants growing at a site known as Tucker. We propagated the seeds to produce ten half-sibling families. The seeds from one wild plant are half-siblings because they have a known mother (maternal line) but an unknown source of pollen. The seedlings (n = 153) were arranged into eight randomized blocks. The soil treatment involved adding 30 mL of sieved native Tucker soil to the experimental pots. The control pots received 30 mL of the regular soil mixture. The plants were moved outside in May 2024 to allow for natural pollination. In July through October, they were brought back into the greenhouse for seed collection. After seed collection was accomplished, we measured the height, maximum width, basal stem diameter, and shoot weight of the plants. We analyzed our data using ANOVA and correlation analyses. Maximum width was 15% greater for plants grown with the Tucker soil addition compared to the controls (p = 0.046). Shoot weight was 21% greater for plants grown with the Tucker soil addition compared to the controls (p < 0.001). Additionally, shoot weight differed among the 10 half-sibling families (p = 0.002). For example, the family with the largest average shoot weight had an average that was 56% greater than the family with the smallest average shoot weight. Finally, when we looked only at the 59% of plants that produced seeds (n = 90), total seed production per plant was positively correlated with shoot weight (r = 0.226, p = 0.034) and average basal stem diameter (r = 0.210, p = 0.049). Our study shows that the addition of native soil can improve clay phacelia growth in terms of maximum plant width and shoot weight. Additionally, shoot weight shows genetic variation among half-sibling families. Although the addition of native soil didn’t increase seed production directly, our study shows that total seed production can be positively correlated with growth metrics such as shoot weight and average basal stem diameter. These findings increase our understanding of the growth and reproduction of clay phacelia, as well as its genetic variation. Such findings can be used to inform conservation efforts for this endangered plant.