Physiological adjustment of two full-sib families of ponderosa pine to elevated CO2
1993
Grulke, N.E. | Hom, J.L. | Roberts, S.W.
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 microliter 1-1) or elevated (700 micromole 1-1) 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 micromole CO2 m-2 S-1) and apparent quantum efficiency (0.082 +/- 0.011 versus 0.045 +/- 0.003 micromole CO2 micromole-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
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