Boyd Deep Canyon Desert Research Center

26 Mar, 10 AM - 28 Mar, 04 AM

The goal of this study is to understand the significance of short-term increases in leaf temperature, which may be associated with periodic wind lulls or extreme temperature events, on the thermal stability of the photosynthetic pathway. A comparison of desert plants in the Mojave and Sonoran deserts to nearby alpine communities will be the basis of this study. The methodology involves the determination of the intrinsic photosynthetic thermotolerance of desert and alpine species in the laboratory by measuring the temperature-dependent increase in fluorescence. In addition, leaf temperatures for each species will be measured in the field. The hypothesis of this study is species that occupy lower elevations and consequently experience warmer leaf temperatures will have greater photosynthetic thermotolerance (measured by the temperature-dependent increase in fluorescence) when compared to species that occupy higher elevations and consequently experience cooler temperatures. Additionally, species found at lower elevations should be able to better recover from heat stress than species found at higher elevations (measured by an decrease in fluorescence after the heat stress). The temperature dependent decline in the photochemical efficiency of photosystem II (PSII) will be used as a metric of comparison between species for photosynthetic thermal tolerance. The photochemical efficiency of PSII will be quantified using the ratio of variable to maximal fluorescence (Fv/Fm) following actinic light pulses using a fluorometer. A minimum of four species at two different locations will be sampled during a visit to the reserve. A minimum of 18 different locations over six months will be sampled. Leaf canopy temperature will be measured for each location as well as leaf temperature. For the Fv/Fm measurements, a minimum of fifty leaves will be randomly collected from at least five different individuals for each species. Leaves will be collected by removing short sections of branches. An overview of the protocol for determination of intrinsic photosynthetic thermotolerance and recovery from heat stress 1. Keep stems in plastic bags at room temperature and in the dark. 2. Remove leaves and place in a plastic bag at room temperature and dark for 30minutes. Measure Fv/Fm. 3. Place leaves in a control bath (28 C) for 15 minutes under sub-saturated light. Measure Fv/Fm. 4. Place leaves into a water bath for 15 minutes at different temperatures (46 C, 48 C, 50 C, 52 C, and 54 C) under sub-saturated light. Measure Fv/Fm. 5. Place leaves back into the control bath (28 C) for 90 minutes under sub-saturated light. Measure Fv/Fm. 6. Place leaves back in dark for 15 minutes. Measure Fv/Fm. 7. Place leaves in dark overnight. Measure Fv/Fm the following morning. An overview of temperature data collection in the field 1. Leaf temperatures will recorded using a thermocoupler sensor attached directly to a leaf. Temperature data will be recorded with a Campbell data logger. 2. Leaf canopy temperature will be recorded with an Onset Pendant data logger. Several data loggers will be deployed at each location for 2-3 days. 3. Leaf temperature and leaf canopy temperature will be collected continuously for 2-3 days for each location.

Visit #31573 @Boyd Deep Canyon Desert Research Center

Approved

Under Project # 27095 | Research

Ecological Analysis of Photosynthetic Thermotolerance

graduate_student - California Polytechnic State University (CSU), San Luis Obispo

Reservation Members(s)

David Gallagher Mar 26 - 28, 2013 (3 days)
Charles Knight Mar 26 - 28, 2013 (3 days)
Group of 2 Graduate Student Mar 26 - 28, 2013 (3 days)

Reserve Resources(s) | Create Invoice

Lab Space 1 Mar 26 - 28, 2013
Mayhew housing facilities 2 Mar 26 - 28, 2013