Super-elevated CO2 interferes with stomatal response to ABA and night closure in soybean (Glycine max)

• Published in: Journal of plant physiology Vol. 166; no. 9; pp. 903 - 913
• Main Authors: Levine, Lanfang H, Richards, Jeffrey T, Wheeler, Raymond M
• Format: Journal Article
• Language: English
• Published: Germany 01.06.2009
• Subjects: abscisic acid; Abscisic Acid - pharmacology; carbon dioxide; Carbon Dioxide - pharmacology; Gene Expression Regulation, Plant - drug effects; Gene Expression Regulation, Plant - physiology; Glycine max; Glycine max - drug effects; Glycine max - metabolism; Glycine max - physiology; physiological response; Plant Leaves - drug effects; Plant Leaves - metabolism; Plant Leaves - physiology; plant response; Plant Stomata - drug effects; Plant Stomata - physiology; Plant Transpiration - drug effects; Plant Transpiration - physiology; signal transduction; soybeans; starch; stomata; stomatal conductance; stomatal movement
• ISSN: 0176-1617; 1618-1328
• DOI: 10.1016/j.jplph.2008.11.006

Studies have shown stomatal conductance (g(s)) of plants exposed to super-elevated CO2 (>5000 μmol mol-1) increases in several species, in contrast to a decrease of g(s) caused by moderate CO2 enrichment. We conducted a series of experiments to determine whether super-elevated CO2 alters stomatal development and/or interferes with stomatal closure in soybean (Glycine max). Plants were grown at nominal ambient (400), elevated (1200) and super-elevated (10,000 μmol mol-1) CO2 in controlled environmental chambers. Stomatal density of the plant leaf was examined by a scanning electron microscope (SEM), while the stomatal response to the application of exogenous abscisic acid (ABA), a phytohormone associated with water stress and stomatal control, was investigated in intact growing plants by measuring the g(s) of abaxial leaf surfaces using a steady-state porometer. Relative to the control (400 μmol mol-1 CO2) plants, daytime stomatal conductance (g(s,day)) of the plants grown under 1200 and 10,000 μmol mol-1 CO2 was reduced by 38% and 15%, respectively. Dark period stomatal conductance (g(s,night)) was unaffected by growing under 1200 μmol mol-1 CO2, but dramatically increased under 10,000 μmol mol-1 CO2. Stomatal density increased by 10% in the leaves of 10,000 μmol mol-1 CO2-grown plants, which in part contributed to the higher g(s,night) values. Elevating [CO2] to 1200 μmol mol-1 enhanced ABA-induced stomatal closure, but further increasing CO2 to 10,000 μmol mol-1 significantly reduced ABA-induced stomatal closure. These results demonstrated that stomatal response to ABA is CO2 dependent. Hence, a stomatal failure to effectively respond to an ABA signal and to close at night under extremely high CO2 may increase plants susceptibility to other abiotic stresses.