Physiological adjustment of two full-sib families of ponderosa pine to elevated CO₂

Abstract

Seeds from two full-sib families of ponderosa pine (Pinus ponderosa) with known differences in growth rates were germinated and grown in an ambient (350 µl l^-1) or elevated (700 µl I^-1) CO₂ concentration. Gas exchange at both ambient and elevated CO₂ concentrations was measured 1,6,39, and 112 days after the seed coat was shed. Initial stimulation of CO₂ exchange rate (CER) by elevated CO₂ was large (> 100%). On Day 1, CER of seedlings grown in elevated CO₂ and measured at ambient CO₂ was significantly lower than the CER of seedlings grown and measured at ambient CO₂, indicating physiological adjustment of the seedlings exposed to elevated CO₂. Physiological acclimation to elevated CO₂ was complete by Day 39 when there was no significant difference in CER between seedlings grown and measured at ambient CO₂ and seedlings grown and measured at elevated CO₂. After 4 months, the light response of seedlings in the two treatments was determined at both ambient and elevated CO₂. Light compensation point, CER at light saturation, and apparent quantum efficiency of seedlings grown and measured at ambient CO₂ were not significantly different from those of seedlings grown and measured at elevated CO₂. With a short-term increase in CO₂, CER at light saturation (5.16 ± 0.52 versus 3.13 ± 0.30 µmol CO₂ m^-2 s^-1) and apparent quantum efficiency (0.082 ± 0.011 versus 0.045 ± 0.003 µmol CO₂ µmol^-1 quanta) were significantly increased. Leaf C/N ratio was significantly increased in the elevated CO₂ treatment. There were few significant differences between families for any response to elevated CO₂. Under the experimental conditions, high growth rate was not correlated with a greater response to elevated CO₂.

Citation

Grulke, N.E.; Hom, J.L.; Roberts, S.W. 1993. Physiological adjustment of two full-sib families of ponderosa pine to elevated CO_2. Tree Physiology. 12: 391-401.