The response of photosynthetic model parameters to temperature and nitrogen concentration in Pinus radiata D. Don |
| |
Authors: | A. S. WALCROFT D. WHITEHEAD W. B. SILVESTER F. M. KELLIHER |
| |
Affiliation: | Biological Sciences Department, University of Waikato, Private Bag 3105, Hamilton, New Zealand;Manaaki Whenua Landcare Research, PO Box 69, Lincoln 8152, New Zealand |
| |
Abstract: | Responses of photosynthesis (A) to intercellular CO2 concentration (ci) in 2-year-old Pinus radiata D. Don seedlings were measured at a range of temperatures in order to parametrize a biophysical model of leaf photosynthesis. Increasing leaf temperature from 8 to 30°C caused a 4-fold increase in Vcmax, the maximum rate of carboxylation (10.7–43.3 μol m?2 s?1 and a 3-fold increase in Jmax, the maximum electron transport rate (20.5–60.2 μmol m ?2 s?1). The temperature optimum for Jmax was lower than that for Vcmax, causing a decline in the ratio Jmax:Vcmax from 2.0 to 1.4 as leaf temperature increased from 8 to 30°C. To determine the response of photosynthesis to leaf nitrogen concentration, additional measurements were made on seedlings grown under four nitrogen treatments. Foliar N concentrations varied between 0.36 and 1.27 mol kg?1, and there were linear relationships between N concentration and both Vcmax and Jmax. Measurements made throughout the crown of a plantation forest tree, where foliar N concentrations varied from 0.83 mol kg?1 near the base to 1.54 mol kg?1 near the leader, yielded similar relationships. These results will be useful in scaling carbon assimilation models from leaves to canopies. |
| |
Keywords: | Pinus radiata modelling nitrogen photosynthesis temperature |
|
|