Effects of light and elevated atmospheric CO/sub 2/ on the ribulose bisphosphate carboxylase activity and ribulose bisphosphate level of soybean leaves

Journal Article · Sat Jan 01 00:00:00 EST 1983 · Plant Physiol.; (United States)

OSTI ID:6328553

Vu, C V; Allen, Jr, L H; Bowes, G

Soybean (Glycine max L. Merr. cv Bragg) was grown throughout its life cycle at 330, 450, and 800 microliters CO/sub 2/ per liter in outdoor controlled-environment chambers under solar irradiance. leaf ribulose-controlled-environment chambers under solar irradiance. Leaf ribulose-1,5-bisphosphate carboxylase (RuBPCase) activities and ribulose-1,5-bisphosphate (RuBP) levels were measured at selected times after planting. Growth under the high CO/sub 2/ levels reduced the extractable RuBPCase activity by up to 22%, but increased the daytime RuBP levels by up to 20%. Diurnal measurements of RuBPCase (expressed in micromoles CO/sub 2/ per milligram chlorophyll per hour) showed that the enzyme values were low (230) when sampled before sunrise, even when activated in vitro with saturating HCO/sub 3//sup /minus// and Mg/sup 2 +/, but increased to 590 during the day as the solar quantum irradiance (photosynthetically active radiation or PAR, in micromoles per square meter per second) rose to 600. The nonactivated RuBPCase values, which averaged 20% lower than the corresponding HCO/sub 3//sup /minus// and Mg/sup 2 +/-activated values, increased in a similar manner with increasing solar PAR. The per cent RuBPCase activation (the ratio of nonactivated to maximum-activated values) increased from 40% before dawn to 80% during the day. Leaf RuBP levels (expressed in nanomoles per milligram chlorophyll) were close to zero before sunrise but increased to a maximum of 220 as the solar PAR rose beyond 1200. These results indicate that, in soybean leaves, light may exert a regulatory effect on extractable RuBPCase in addition to the well-established activation by CO/sub 2/ and Mg/sup 2 +/. 29 refs., 5 figs.

• Research Organization: Department of Agronomy (C.V.V.), US Department of Agriculture-Agricultural Research Service (L.H.A.); Department of Botany (G.B.), University of Florida, Gainesville, Florida 32611
• OSTI ID: 6328553
• Journal Information: Plant Physiol.; (United States), Vol. 73
• Country of Publication: United States
• Language: English

Related Subjects

54 ENVIRONMENTAL SCIENCES
CARBON DIOXIDE
SATURATION
GREENHOUSE EFFECT
EVALUATION
RIBULOSE
REACTION KINETICS
DAILY VARIATIONS
LEAVES
PHOTOSYNTHESIS
SOYBEANS
CARBOHYDRATES
CARBON COMPOUNDS
CARBON OXIDES
CHALCOGENIDES
CHEMICAL REACTIONS
FOOD
KETONES
KINETICS
MONOSACCHARIDES
ORGANIC COMPOUNDS
OXIDES
OXYGEN COMPOUNDS
PENTOSES
PHOTOCHEMICAL REACTIONS
PLANTS
SACCHARIDES
SYNTHESIS
VARIATIONS
VEGETABLES
500200* - Environment
Atmospheric- Chemicals Monitoring & Transport- (-1989)