Thermochimica Acta, Vol.422, No.1-2, 69-74, 2004
Stress and respiration traits differ among four geographically distinct Pinus ponderosa seed sources
This study tested the hypotheses that plant respiration and photosynthesis are genetically adapted to the native climate and that plant metabolism has little ability to acclimate to a non-native climate. Seeds from four geographically distinct seed sources (Oregon, Willamette and Deschutes and California, Mendocino and Eldorado) were used to grow 2-year-old seedlings of ponderosa pine (Pinus ponderosa var. ponderosa) in a common garden near Corvallis, Oregon. Respiratory heat and CO2 rates were measured on elongating shoot tips at five temperatures from 15 to 35 degreesC. Heat and CO2 rates did not differ significantly among the four seed sources when compared at a given temperature. Arrhenius temperature coefficients of heat and CO2 rates of the Deschutes plants were significantly greater than those of the other three sources. Deschutes has the coldest, driest and most variable climate of the four sources. Carbon isotope ratios obtained on the same samples showed greater fractionation in the Mendocino plants than in the other three sources. Mendocino is a coastal site and the results show these plants experienced more stress when grown in the interior common garden site. Because acclimation to growth in a common garden did not erase significant differences in respiratory and photosynthetic properties, the results show that respiration and photosynthesis are genetically adapted to the native climate of the seed source. (C) 2004 Elsevier B.V. All rights reserved.