Leaf magnesium alters photosynthetic response of low water potentials in sunflower

Journal Article · Sat Aug 01 04:00:00 EDT 1987 · Plant Physiology; (USA)

DOI:https://doi.org/10.1104/pp.84.4.1214· OSTI ID:7100818

Rao, I M; Sharp, R E; Boyer, J S ^[1]

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1. Univ. of Illinois, Urbana (USA)

We grew sunflower (Helianthus annuus L.) plants in nutrient solutions having nutritionally adequate but low or high Mg{sup 2+} concentrations and determined whether photosynthesis was effected as leaf water potentials ({psi}{sub w}) decreased. Leaf Mg contents were 3- to 4-fold higher in the plants grown in high Mg{sup 2+} concentrations (10 millimolar) than in those grown in low concentrations (0.25 millimolar). These contents were sufficient to support maximum growth, plant dry weight, and photosynthesis, and the plants appeared normal. As low {psi}{sub w} developed, photosynthesis was inhibited but more so in high Mg leaves than in low Mg leaves. The effect was particularly apparent under conditions of light- and CO{sub 2}-saturation, indicating that the chloroplast capacity to fix CO{sub 2} was altered. The differential inhibition observed in leaves of differing Mg contents was not observed in leaves having differing K contents, suggesting that the effect may have been specific for Mg. Because Mg{sup 2+} inhibits photophosphorylation and coupling factor activities at concentrations likely to occur as leaves dehydrate, Mg may play a role in the inhibition of chloroplast reactions at low {psi}{sub w}, especially in leaves such as sunflower that markedly decrease in water content as {psi}{sub w} decreases.

• DOE Contract Number: FG05-84ER13273
• OSTI ID: 7100818
• Journal Information: Plant Physiology; (USA), Journal Name: Plant Physiology; (USA) Vol. 84:4; ISSN 0032-0889; ISSN PLPHA
• Country of Publication: United States
• Language: English

Related Subjects

550500* -- Metabolism
59 BASIC BIOLOGICAL SCIENCES
ALKALINE EARTH METALS
BIOLOGICAL EFFECTS
CARBON DIOXIDE FIXATION
CELL CONSTITUENTS
CHEMICAL REACTIONS
CHLOROPLASTS
ELEMENTS
LEAVES
MAGNESIUM
MAGNOLIOPHYTA
MAGNOLIOPSIDA
METALS
PHOTOCHEMICAL REACTIONS
PHOTOSYNTHESIS
PLANTS
SUNFLOWERS
SYNTHESIS