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Undergraduate Student Research
2013
Difference in Water Status between Oak Trees
(Quercus berberidifolia) with Brown and Green
Leaves During Severe Drought
Mia Bryant
Pepperdine University
Hannah Dario
Pepperdine University
Cameron Kline
Pepperdine University
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Recommended Citation
Bryant, Mia; Dario, Hannah; and Kline, Cameron, "Difference in Water Status between Oak Trees (Quercus berberidifolia) with
Brown and Green Leaves During Severe Drought" (2013). Pepperdine University, All Undergraduate Student Research. Paper 127.
http://digitalcommons.pepperdine.edu/sturesearch/127
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Difference in Water Status between Oak Trees (Quercus berberidifolia) with Brown and Green Leaves During Severe Drought Mia Bryant, Hannah Dario and Cameron Kline Mentor: Dr. Stephen D. Davis Pepperdine University, 24255 Pacific Coast Highway, Malibu, CA 90263 Abstract Methods 1. • 
2. In this experiment, we examined cavita>on in Quercus berberidifolia plants. We hypothesized that as the amount of water stress increases, then the pressure to cause embolism will decrease. We thought this because as a plant loses more water, the more air bubbles will form within the plant and therefore the Figure 2. With the use of a parometer, we Figure 1. Data was collected by using the pressure to cause this will decrease. We tested this measured the temperature of the green and Scholander Hammel pressure chamber to measure hypothesis by comparing dry Quercus berberidifolia to the pressure inside the leaf before it was cut from brown leaves along with their conductance at consistent temperatures. the o
riginal s
hrub o
ak. more hydrated Quercus berberidifolia in Tapia Park, near Malibu, California. We measured and compared 3. Fluorescence was also measured using a fluorometer to measure the light reflec>on of green and brown leaves. these plants by the use of the Scholander Pressure Results chamber and a parometer. In the end, we discovered that our hypothesis was correct. Our data showed us Predawn
Midday
that less hydrated plants that had more water stress had a lower atmospheric pressure than the more *
*
hydrated plants. IntroducEon 9
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Discussion Dry chaparral species that are geWng significantly dryer There was a significant difference between green stems and brown stems regarding the atmospheric pressure at which the stems fall off Data showed that the pressure was higher in brown leaves at pre-­‐dawn and mid-­‐day The pressure at which the stem was cut is measured in bars at atmospheric pressure Conclusion We have concluded that the atmospheric pressure at which plant stems and leaves are falling off to further the plant survival. The plants with brown and green leaves show significantly different pressures. In order to determine whether the change in pressure was significant, we ran tests and acquired data. As these plants get dryer, the pressure at which they fall off increased. An increasing problem around in the world is drought. This is most evident in the Santa Monica Mountains. In this Mediterranean style climate, there are consistent periods of drought which are increasing Green
Brown
Green
Brown
throughout the years. These dry condi>ons cause the Figure 3. Mean water poten>al at Predawn and Midday comparing shrub oaks with green leaves chaparral vegeta>on to become less hydrated and as a versus ones with brown leaves, growing at Tapia Park near Malibu, California. Error bars result cavita>on occurs. Cavita>on in a plant is when represent ± 1 SE, n = 6 and an asterisk indicates significant difference between plants with green leaves versus brown leaves by Student T-­‐test, p < 0.05. the loss of water causes an empty space or a low References pressure bubble to form. Conductance
McDowell, Nate, William T. Pockman, Fluorescence
Through inves>ga>ng the rela>onship between Craig D. Allen, David D. Breshears, Neil water stress and the amount of pressure for embolism Cobb, Thomas Kolb, Jennifer Plaut et al. to occur, we can understand more the impact of 2008. "Mechanisms of plant survival and cavita>on of leaves, and the drought impacts on plants *
mortality d
uring d
rought: w
hy d
o s
ome in the chaparral environment. In this experiment, we *
plants survive while others succumb to observed and tested the extent of cavita>on in drought?." New Phytologist 178, no. 4: Quercus agrifolia. We compared dry Quercus agrifolia 719-­‐739. with more hydrated Quercus agrifolia. We hypothesized that as the amount of water stress Brown
Brown
Green
Green
increases, then the pressure to cause embolism will Figure 4. The conductance of green leaves Figure 3. Fluorescence comparing shrub oaks decrease. We tested this hypothesis through four compared to brown leaves of the shrub oak, taken with green leaves versus shrub oaks with brown leaves, taken at Tapia Park near Malibu, different tests with the use of a Scholander pressure at Tapia Park near Malibu, California. Error bars represent ± 1 SE, n = 6 and an asterisk indicates California. Error bars represent ± 1 SE, n = 18 chamber, parometer, and a fluorometer. These tests significant difference between plants with green and an asterisk indicates significant difference were all conducted Tapia Park, near Malibu, California. leaves versus plants with brown leaves by Student t-­‐ between plants with green leaves versus 3
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110
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test, p < 0.05. plants with brown leaves by student t-­‐test, p < 0.05.