PARENT SESSION
Oral Session # 64: Plant Ecology V: Physiology and Function II.
Presiding: G North
Thursday, August 7. 8:00 AM to 11:30 AM, SITCC Meeting Room 102.

Stress and respiration traits differ among four geographically distinct Pinus ponderosa seed sources.

Keller, Emily^*,1, Anekonda, Thimmappa², Smith, Bruce¹, Hansen, Lee ¹, St. Clair, J. Brad³, Criddle, Richard¹, ¹ Brigham Young University, Provo, Utah² Oregon State University, Corvallis, Oregon³ USDA Forest Service, Corvallis, Oregon

ABSTRACT- This study shows that plants adapt their metabolism to specific environmental temperatures (their native climate) and that plants respond to both their environment and their genetics. This was done using calorimetry and stable isotopic fractionation. Two-year old seedlings from each of four geographically distinct ponderosa pine (Pinus ponderosa var. ponderosa) seed sources were studied. Two sources are from Oregon (Willamette and Deschutes) and two sources are from California (Mendocino and Eldorado). Dark metabolic heat and CO₂ production rates were measured on tissue from elongating shoot tips at five temperatures from 15 to 35 degrees C. Heat and CO₂ production rates were not significantly different among the four seed sources, but temperature coefficients of both heat and CO₂ production rates were higher in the Deschutes seed source than in the other three sources. The Deschutes seed source is the coldest, driest and most variable climate of the four sources. Climates of the other three seed sources are very similar. The ¹³C values were then obtained on the same samples to determine the degree of stress associated with growth in different locations. Small differences in fractionation indicate variation in plant stress. The fractionation ratios were lower in the Mendocino seed source than in the other three sources, which were all very similar to each other.

Key words: isotope fractionation, calorimetry