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Title: EFFECTS OF ATMOSPHERIC CO2 ENRICHMENT ON CHLOROPHYLL AND NITROGEN CONCENTRATIONS OF SOUR ORANGE TREE LEAVES.

Author
item Idso, Sherwood
item Kimball, Bruce
item Hendrix, Donald

Submitted to: Plant Cell and Environment
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/14/1996
Publication Date: N/A
Citation: N/A

Interpretive Summary: How will the rising CO2 content of earth's atmosphere affect the ability of citrus trees to acquire the nitrogen they need to synthesize chlorophyll and carry out their normal growth processes? Results of an experiment designed to address this question were very positive. They showed a given area of leaf from trees exposed to air containing 75% more CO2 than trees growing in normal air to contain 4.8% less nitrogen and chlorophyll than an equivalent area of leaf from non-CO2-enriched trees. Adjusting for the larger size of the leaves in the CO2-enriched trees, and accounting for their greater numbers, we calculated that each tree exposed to the 75% extra CO2 had 75% more nitrogen and chlorophyll in all of its leaves than did each tree growing in normal air. This advantage, combined with the higher efficiencies with which nitrogen and chlorophyll are utilized by the CO2-enriched trees, has allowed them to grow two times larger than the trees exposed to normal air. As the air's CO2 content seems destined to rise ever higher in the years ahead, such consequences bode well for the citrus industry and consumers of their products.

Technical Abstract: At weekly intervals throughout years 4 through 7 of our continuing long- term study of the effects of a 300 umol mol-1 enrichment of the air's CO2 content on sour orange tree growth and development, we measured chlorophyll a contents of 60 leaves on each of 8 trees with a hand-held chlorophyll meter that was specifically calibrated for the trees of our study. At bi-monthly intervals we also measured the areas, dry weights and nitrogen contents of 68 leaves from each tree. Expressed on a per- unit-leaf-area basis, and averaged over the four-year period, leaves from the CO2-enriched trees contained 4.8% less chlorophyll and nitrogen than leaves from the ambient-treatment trees.