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Fall 2012

A comparison of Brittlebush (Encelia farinosa) productivity and health during drought and post rainfall

Gabi DiCiolli Pepperdine University

Karre Lawson Pepperdine University

Anders Reimer Pepperdine University

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Part of the Plant Biology Commons

Recommended Citation DiCiolli, Gabi; Lawson, Karre; and Reimer, Anders, "A comparison of Brittlebush (Encelia farinosa) productivity and health during drought and post rainfall" (2012). Pepperdine University, Featured Research. Paper 52. https://digitalcommons.pepperdine.edu/sturesearch/52

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A comparison of Brilebush (Encelia farinosa) producvity and health during drought and post rainfall Gabi DiCiolli, Karre Lawson, Anders Reimer Pepperdine University, Malibu, CA, 90263

Results Abstract Methods Encelia farinosa is well adapted for drought tolerance as its leaves •During a dry period (no rain or irrigaon 2 weeks prior), use the LI- transform color based on water availability. We were puzzled by a COR 6400XT to measure photosynthec rate, conductance, queson that any desert botanist must consider. How does the transpiraon, fluorescence, intercellular CO2 concentraon, photosynthec efficiency of E. farinosa fluctuate as it transions photochemical and nonphotochemical quenching, electron transport from a state of drought to a state of soil saturaon within a 72 rate, and quantum yield from two leaves apiece from six brilebush hour period? In this experiment we looked at the effects of plants irrigaon on the health and quantum yield of the brilebush by Collecon me: 8:30 am, site: Drescher hill, light level: 1200 looking at photosynthec rates using the portable photosynthesis µmol m-2 s-1, CO2 level: 400 ppm, temperature: 25° C system LI-COR 6400 when applied to two leaves on a given plant • Take photographs of bush leaves for color comparison and water potenal (ψ) using a Scholander-type pressure chamber • Clip two twigs from each bush and measure water potenal with on the stems. Scholander-Hammel presure chamber We aempted to understand how quickly these processes take • Cover control bush with clear tarp to prevent accidental irrigaon place from pre-rainfall condions to post-rainfall condions up to • Wait for heavy rainfall, then record new data within 24 hours and 72 hours aer. We concluded that E. farinosa does not fluctuate again at 72 hours significantly in terms of photosynthec rate, transpiraon, and quantum yield with dry as opposed to irrigated soil. However, transpiraon and quantum yield significantly increased for the first 24 hours immediately following rainfall, leading us to speculate Conclusion whether the plant operates at peak efficiency within this window. • Stem water potenal was not stascally different before and aer rainfall. Table 1. Plant health and photosynthec efficiency before and aer rainfall. Readings from the LI-COR 6400XT and Scholander-Hammel pressure chamber • There was no significant difference in photosynthec rate before and aer rainfall. Introducon • Plant health improved over the 72 hour period post rainfall. Extreme elements can cause stress on a plant and overexeron • The peak quantum yield and transpiraon rate occurred 24 hours may lead to death. When exposed to extreme condions, plants post rainfall. must evolve to exhibit characteriscs that will allow them to • The color intensity of leaves and photosynthec output of irrigated withstand such environments and prosper to the next generaon. plants were greater than those of the non-irrigated (control) plant. Encelia farinosa, more commonly known as Brilebush, is a small perennial desert shrub from the sunflower family found throughout the southwestern region of the United States and the Northwestern region of Mexico. Due to its drought and heat tolerance it has become a popular landscaping plant (Bang et al. Literature Cited Figure 1. Average transpiraon rates of 6 E. farinosa bushes over 3 Bang,C., Sabo, J.L., Faeth, S.H. 2010. Reduced Wind Speed Improves Plant Growth in a Desert 2010). City. PLoS ONE 5(6): e11061 days Ehleringer, J.R.1982. The influence of water stress and temperature on leaf pubescence The brilebush is well adapted for drought tolerance because its development in Encelia farinosa. American Journal of Botany. 69: 670-675 Ehleringer, J.R. 1984. Intraspecific compeve effects on water relaons, growth and leaves transform color based on how irrigated the surrounding soil reproducon in Encelia farinosa. Oecologia. 63:153-8 is (Ehleringer 1984; Nobel et al. 1998) and in extreme cases, it will Ehleringer, J.R., Cook C.S. 1990. Characteriscs of Encelia species differing in leaf reflectance and shed its leaves altogether. Well-hydrated soil confers a greenish transpiraon rate under common garden condions. Oecologia. 84:484-9 Nobel, P.S., Zhang, H., Sharifi, R., Castañeda, M., Greenhouse B. 1998. Leaf expansion, net CO2 gray hue to leaves, whereas poorly irrigated plants bear a whish uptake, Rubisco acvity, and efficiency of long-term biomass gain for the common desert gray hue. This mechanism is adapted for defense against water subshrub Encelia farinosa. Photosynthesis Research. 56:67-73 Figure 2. Analysis of Figure 1 using Zhang, H., Sharifi, M.R., Nobel, P.S. 1995. Photosynthec Characteriscs of Sun Versus Shade loss through transpiraon. Darker leaves are less reflecve and Plants of Encelia farinosa as Affected by Photosynthec Photon Flux Density, Intercellular C02 absorb more light which translates into more available energy for one-way ANOVA. Excludes data from Concentraon, Leaf Water Potenal, and Leaf Temperature. Australian Journal of Plant control group photosynthesis (Zhang et al. 1995). Conversely, lighter colored Physiology. 22: 833-41 leaves reflect more light and decrease metabolic levels (Ehleringer and Cook 1990). When the plant is surrounded by soil that is irrigated very well, it is more energecally cost efficient for it to Acknowledgements revert back to a green leaved state to condone maximizing We wish to thank Dr. Stephen Davis for assistance and guidance with the project. We would also like to thank the Naonal photosynthec rates. Figure 4. Analysis of Figure 3 using one-way Science Foundaon, the W.M. Keck Foundaon, and the Natural Science Division of Pepperdine University for the much ANOVA. Excludes data from control group needed grants to aain equipment necessary in this project. Figure 3. Photosynthec rate of 6 E. farinosa This experiment seeks to invesgate E. farinosa’s health and bushes over 3 days producvity while transioning from white to green leaves by measuring photosynthec acvity, quantum yield and transpiraon before and aer irrigaon of previously dehydrated soil.

Figure 7. Comparison of leaf color Figure 6. Analysis of Figure 5 using Pre-rainfall leaves were brile and white (le). A day aer the rain, the plants started one-way ANOVA. Excludes data from Figure 5. Average quantum yield of 6 E. farinosa bushes over 3 days becoming significantly more green and flexible (middle). Aer 3 days (right) the leaves are control group slightly more colorful than they were the day aer the rain.