Document: DAV-3-34-10

Effects of elevated CO₂ and supplemental nitrogen on photosynthesis and productivity of the Mojave Desert annual, Camissonia claviformis.

HOUSMAN, D.C.*, A.RAMOS and S.D.SMITH

University of Nevada, Las Vegas, NV 89154-4004 ¹

Abstract:
Camissonia claviformis is a winter annual that has extremely high photosynthetic capacity and leaf N content under natural conditions in the Mojave Desert. In this study, we asked the question if elevated CO₂ and increased nitrogen deposition would significantly increase these already high rates of photosynthesis and growth. Camissonia plants were grown from seed in a glasshouse at two levels of atmospheric CO₂ (360 and 700ppm) and nitrogen (1:40 and 1:80 N dilutions of Hoagland's), and then harvested at pre-reproductive (maximum leaf area), peak flowering, and seed set. Plant height, leaf area, photosynthetic rate, and leaf water potential were also measured at various stages in the developmental cycle. No significant CO₂ x N effect was found for any of the variables measured, but there were significant CO₂ effects. Although maximum photosynthetic rates (A_max) did not differ at pre-reproduction, plants grown in elevated CO₂ showed significant down-regulation compared to ambient-grown plants at the flowering stage. Plants grown in elevated CO₂ had lower water potentials at the pre-reproductive stage, but this treatment difference did not persist at flowering. There were no significant differences in plant height or leaf area at either pre-reproduction or flowering. At seed set, however, plants grown at elevated CO₂ had significantly greater biomass as a result of greater aboveground growth, and produced 42% more seeds than did ambient-grown plants. These results indicate that predicted future levels of atmospheric CO₂ and nitrogen deposition may lead to even greater productivity, reproductive activity, and seed rain in desert annuals.

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This abstract is being presented at: 10:30 AM in session:
Poster Session #18: Elevated CO₂.