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Effects of doubled atmospheric carbon dioxide concentration on the responses of assimilation and conductance to humidity
Author(s) -
BUNCE J. A.
Publication year - 1993
Publication title -
plant, cell and environment
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.646
H-Index - 200
eISSN - 1365-3040
pISSN - 0140-7791
DOI - 10.1111/j.1365-3040.1993.tb00860.x
Subject(s) - amaranth , carbon dioxide , sunflower , partial pressure , conductance , stomatal conductance , chemistry , helianthus annuus , assimilation (phonology) , humidity , relative humidity , zoology , orchard , agronomy , horticulture , botany , photosynthesis , biology , food science , meteorology , oxygen , mathematics , linguistics , organic chemistry , philosophy , combinatorics , physics
ABSTRACT Experiments were performed to determine if growth at elevated partial pressure of CO 2 altered the sensitivity of leaf water vapour conductance and rate of CO 2 assimilation to the leaf‐to‐air difference in the partial pressure of water vapour (Δw). Comparisons were made between plants grown and measured at 350 and 700 μPa Pa −1 partial pressures of CO 2 for amaranth, soybean and sunflower grown in controlled environment chambers, soybean grown outdoors in pots, and orchard grass grown in field plots. In amaranth, soybean and orchard grass, both the absolute and the relative sensitivity of conductance to Δw at the leaf surface were less in plants grown and measured at the elevated CO 2 . In sunflower, there was no change in the sensitivity of conductance to Δw for the two CO 2 partial pressures. Tests in soybeans and amaranth showed that the change in sensitivity resulted from elevated CO 2 during the measurement of the Δw response. Assimilation rate of CO 2 was not altered by Δw in amaranth, which has C 4 metabolism. In sunflower, the assimilation rate of plants grown and measured at elevated CO 2 was insensitive to Δw, consistent with the response of assimilation rate to intercellular CO 2 partial pressure in the prevailing range. In soybean, the sensitivity of assimilation rate to Δw was not different between CO 2 treatments, in contrast to what would be expected from the response of assimilation rate to intercellular CO 2 partial pressure.