Mild water stress effects on carbon-reduction-cycle intermediates, ribulose bisphosphate carboxylase activity, and spatial homogeneity of photosynthesis in intact leaves

Journal Article · Sat Apr 01 04:00:00 EST 1989 · Plant Physiology; (USA)

DOI:https://doi.org/10.1104/pp.89.4.1060· OSTI ID:6895068

Sharkey, T D; Seemann, J R ^[1]

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1. Univ. of Wisconsin, Madison (USA) Univ. of Nevada, Reno (USA)

We have examined the effect of mild water stress on photosynthetic chloroplast reactions of intact Phaseolus vulgaris leaves by measuring two parameters of ribulose bisphosphate (RuBP) carboxylase activity and the pool sizes of RuBP, 3-phosphoglycerate (PGA), triose phosphates, hexose monophosphates, and ATP. We also tested for patchy stomatal closure by feeding {sup 14}CO{sub 2}. The k{sub cat} of RuBP carboxylase (moles CO{sub 2} fixed per mole enzyme per second) which could be measured after incubating the enzyme with CO{sub 2} and Mg{sup 2+} was unchanged by water stress. The ratio of activity before and after incubation with CO{sub 2} and Mg{sup 2+} (the carbamylation state) was slightly reduced by severe stress but not by mild stress. Likewise, the concentration of RuBP was slightly reduced by severe stress but not by mild stress. The concentration of PGA was markedly reduced by both mild and severe water stress. The concentration of triose phosphates did not decline as much as PGA. We found that photosynthesis in water stressed leaves occurred in patches. The patchiness of photosynthesis during water stress may lead to an underestimation of the effect of stomatal closure. We conclude that reductions in whole leaf photosynthesis caused by mild water stress are primarily the result of stomatal closure and that there is no indication of damage to chloroplast reactions.

• OSTI ID: 6895068
• Journal Information: Plant Physiology; (USA), Journal Name: Plant Physiology; (USA) Vol. 89:4; ISSN 0032-0889; ISSN PLPHA
• Country of Publication: United States
• Language: English

Related Subjects

14 SOLAR ENERGY
140505* -- Solar Energy Conversion-- Photochemical
Photobiological
& Thermochemical Conversion-- (1980-)
550201 -- Biochemistry-- Tracer Techniques
59 BASIC BIOLOGICAL SCIENCES
ATP
BIOLOGICAL STRESS
CARBON 14 COMPOUNDS
CARBON COMPOUNDS
CARBON DIOXIDE
CARBON OXIDES
CARBON-CARBON LYASES
CARBOXY-LYASES
CELL CONSTITUENTS
CHALCOGENIDES
CHEMICAL REACTIONS
CHLOROPLASTS
ENZYME ACTIVITY
ENZYMES
HYDROGEN COMPOUNDS
ISOTOPE APPLICATIONS
LABELLED COMPOUNDS
LEAVES
LEGUMINOSAE
LYASES
MAGNOLIOPHYTA
MAGNOLIOPSIDA
NUCLEOTIDES
OPENINGS
ORGANIC COMPOUNDS
OXIDES
OXYGEN COMPOUNDS
PHASEOLUS
PHOSPHATES
PHOSPHORUS COMPOUNDS
PHOTOCHEMICAL REACTIONS
PHOTOSYNTHESIS
PLANTS
RIBULOSE DIPHOSPHATE CARBOXYLASE
STOMATA
SYNTHESIS
TRACER TECHNIQUES
WATER