Gas Exchange Rate and Yield Responses of Virginia‐type Peanut to Carbon Dioxide Enrichment

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Abstract
Poor seed fill and resultant seed‐coat shriveling occur commonly on Virginia‐type peanut (Arachis hypogaea L.) grown in Taiwan. The phenomenon may be linked to the limitation in photosynthate supply at seed filling. The objective of this study was to evaluate the effect of CO2 enrichment (1000 μL CO2 L−1) and depegging on CO2 exchange rate (CER) and yield responses of pot‐grown Virginia‐type peanut. Carbon dioxide enrichments were applied to the plants at pod filling. Depegging effect was examined contrasting the controls and the plants maintaining 38 to 40 pegs throughout the growing period. The results indicated that short‐term CO2 enrichment (CO2 treatment for 10 d) improved leaf and canopy CER. Long‐term CO2 enrichment (CO2 treatments throughout pod filling) tended to ease leaf ribulose 1,5‐bisphosphate carboxylase/oxygenase (rubisco) and chlorophyll (chl) deteriorations. Electrophoresis patterns of leaf soluble protein extracts confirmed this finding. Seed yield per plant was increased with high CO2 treatment applied at seed‐filling period, but the production of marketable seeds was improved only in the plants receiving CO2 and depegging treatments. The poor seed‐fill characteristic observed in Virginia‐type peanut is attributed to excessive sink load and low canopy CER.