Effects of carbon dioxide concentration and nutrition on photosynthetic functions of white birch seedlings

Abstract

To investigate the interactive effects of atmospheric carbon dioxide concentration ([CO2]) and nutrition on photosynthesis and its acclimation to elevated [CO2], a two-way factorial experiment was carried out with two nutritional regimes (high- and low-nitrogen (N), phosphorus (P) and potassium (K)) and two CO2 concentrations (360 and 720 ppm) with white birch seedlings (Betula papyrifera Marsh.) grown for four months in environment-controlled greenhouses. Elevated [CO2] enhanced maximal carboxylation rate (Vcmax), photosynthetically active radiation-saturated electron transport rate (Jmax), actual photochemical efficiency of photosystem II (PSII) in the light (ΔF/F m′) and photosynthetic linear electron transport to carboxylation (Jc) after 2.5 months of treatment, and it increased net photosynthetic rate (An), photosynthetic water-use efficiency (WUE), photosynthetic nitrogen-use efficiency (NUE) and photosynthetic phosphorus-use efficiency (PUE) after 2.5 and 3.5 months of treatment, but it reduced stomatal conductance (gs), transpiration rate (E) and the fraction of total photosynthetic linear electron transport partitioned to oxygenation (Jo/JT) after 2.5 and 3.5 months of treatment. Low nutrient availability decreased An, WUE, Vcmax, Jmax, triose phosphate utilization (TPU), (Fm′ - F)/Fm′ and Jc, but increased Jo/J T and NUE. Generally, Vcmax was more sensitive to nutrient availability than Jmax. There were significant interactive effects of [CO2] and nutrition over time, e.g., the positive effects of high nutrition on An, Vcmax, Jmax, ΔF/F m′ and Jc were significantly greater in elevated [CO2] than in ambient [CO2]. In contrast, the interactive effect of [CO2] and nutrition on NUE was significant after 2.5 months of treatment, but not after 3.5 months. High nutrient availability generally increased PUE after 3.5 months of treatment. There was evidence for photosynthetic up-regulation in response to elevated [CO2], particularly in seedlings receiving high nutrition. Photosynthetic depression in response to low nutrient availability was attributed to biochemical limitation (or increased mesophyll resistance) rather than stomatal limitation. Elevated [CO2] reduced leaf N concentration, particularly in seedlings receiving low nutrition, but had no significant effect on leaf P or K concentration. High nutrient availability generally increased area-based leaf N, P and K concentrations, but had negligible effects on K after 2.5 months of treatment. © 2006 Heron Publishing.