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Submitted to: Photosynthesis Research
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 5/16/2001 Publication Date: 8/1/2001 Citation: Bunce, J.A. 2001. Seasonal patterns of photosynthetic response and acclimation to elevated carbon dioxide in field-grown strawberry. Photosynthesis Research. 68:237-245. Interpretive Summary: The rising concentration of carbon dioxide in the atmosphere is expected to stimulate the photosynthetic rate of most crop plants, potentially leading to increased growth and yield. However, predictions of the impact of rising atmospheric carbon dioxide on crop growth are highly uncertain, partly because of lack of knowledge about how temperature affects the stimulation of photosynthesis and about the occurrence and magnitude of photosynthetic acclimation to elevated carbon dioxide. Acclimation is the process by which the initial stimulation of photosynthesis by elevated carbon dioxide is lost over time, as plants adjust to the altered conditions. This work tested two specific hypotheses, one concerning the temperature dependence of the stimulation of photosynthesis by elevated carbon dioxide, and another about how acclimation of photosynthesis would vary seasonally. The data indicated that neither hypothesis was correct for this species. The data fit the pattern that photosynthetic acclimation occurred during periods without stress and did not occur during stress. This information will be of use to those predicting the response of the growth of crop plants to the rising concentration of carbon dioxide in the atmosphere. Technical Abstract: Strawberry plants were grown in field plots at the current ambient concentration of carbon dioxide and at two and three times the current concentration. Weekly measurements were made of single leaf gas exchange of upper canopy leaves from early spring through fall of two years, in order to determine the temperature dependence of the stimulation of photosynthesis by elevated carbon dioxide, whether growth at elevated carbon dioxide resulted in acclimation of photosynthesis, and whether any photosynthetic acclimation was reduced when fruiting created additional demand for the products of photosynthesis. Stimulation of photosynthesis by short-term increases in carbon dioxide increased strongly with measurement temperature, but exceeded that predicted from the kinetic characteristics of ribulose-1, 5-bisphosphate carboxylase at all temperatures. Acclimation of photosynthesis to growth at elevated carbon dioxide was evident from early spring through summer, including the fruiting period in early summer, with lower rates under standard measurement conditions in plants grown at elevated carbon dioxide. Photosynthetic acclimation was not evident during dry periods in midsummer, when the elevated carbon dioxide treatments conserved soil water and photosynthesis declined more at ambient than at elevated carbon dioxide, nor in the fall, after frosts had occurred. The data do not support the hypothesis that source-sink balance controls the seasonal occurrence of photosynthetic acclimation to elevated carbon dioxide in this species. |
