It is known that the NDVI can be used as a measure of hydration in plants because of the variation in pigments due to xanthophyll cycling (Schmitz et al., 2013). Flower petals can also exhibit variations in petal reflectance invisible to the naked eye (Fam & Espinoza, 2013). It was hypothesized that overall hydration levels of a plant would correlate to a difference in the pigments produced for petal color, and thus differences in hydration levels would correlate to differences in petal reflectance. To test this hypothesis, three flowers and two stems were collected from ten different E. californica plants, and tested for petal reflectance using a UniSpec spectrophotometer, as well as water potential using the Scholander-Hammel Pressure Chamber. The reflectance was analyzed using a created JCK index, measuring wavelength ranges from 590-610 nm and 680-720 nm. The plant groups were separated into a “high hydration” group and a “low hydration” group with a significant difference in hydration levels, which was determined by a Student’s t-test. A comparison of the JCK index values for these two hydration groups did not support the hypothesis that there would be a difference in reflectance for the two groups. These results are meaningful because of the role of wavelength reflectance on pollinator attraction.
Givens, Jayci M.; Nussbaum, Kaylee A.; and Kawata, Caitin R., "Correlation between Hydration and Reflectance of Yellow Petals on Encelia californica" (2015). Pepperdine University, Featured Research. Paper 203.