1. Down-Regulation of Photosynthesis to Elevated CO2 and N Fertilization in Understory Fraxinus rhynchophylla Seedlings
- Author
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Chanoh Park, Seohyun Kim, Siyeon Byeon, Daun Ryu, Sukyung Kim, Jeonghyun Hong, Kunhyo Kim, Hyun-Seok Kim, Sim-Hee Han, and Chang-Young Oh
- Subjects
Rubisco ,chemistry.chemical_element ,Photosynthesis ,Fraxinus ,nitrogen addition ,chemistry.chemical_compound ,Human fertilization ,leaf nitrogen content ,nonsturctural carbohydrates ,QK900-989 ,Plant ecology ,Biomass (ecology) ,photosynthesis ,biology ,RuBisCO ,fungi ,food and beverages ,Forestry ,Understory ,biology.organism_classification ,Nitrogen ,Horticulture ,chemistry ,understory ,Chlorophyll ,biology.protein - Abstract
(1) Background: Down-regulation of photosynthesis has been commonly reported in elevated CO2 (eCO2) experiments and is accompanied by a reduction of leaf nitrogen (N) concentration. Decreased N concentrations in plant tissues under eCO2 can be attributed to an increase in nonstructural carbohydrate (NSC) and are possibly related to N availability. (2) Methods: To examine whether the reduction of leaf N concentration under eCO2 is related to N availability, we investigated understory Fraxinus rhynchophylla seedlings grown under three different CO2 conditions (ambient, 400 ppm [aCO2], ambient × 1.4, 560 ppm [eCO21.4], and ambient × 1.8, 720 ppm [eCO21.8]) and three different N concentrations for 2 years. (3) Results: Leaf and stem biomass did not change under eCO2 conditions, whereas leaf production and stem and branch biomass were increased by N fertilization. Unlike biomass, the light-saturated photosynthetic rate and photosynthetic N-use efficiency (PNUE) increased under eCO2 conditions. However, leaf N, Rubisco, and chlorophyll decreased under eCO2 conditions in both N-fertilized and unfertilized treatments. Contrary to the previous studies, leaf NSC decreased under eCO2 conditions. Unlike leaf N concentration, N concentration of the stem under eCO2 conditions was higher than that under ambient CO2 (4). Conclusions: Leaf N concentration was not reduced by NSC under eCO2 conditions in the understory, and unlike other organs, leaf N concentration might be reduced due to increased PNUE.
- Published
- 2021