Regulation of Photosynthetic Induction State in High- and Low-Light-Grown Soybean and Alocasia macrorrhiza (L.) G. Don.

Section of Plant Biology, University of California, Davis, California 95616-8537.
Plant physiology (Impact Factor: 7.39). 10/1995; 109(1):307-317.
Source: PubMed

ABSTRACT Alocasia (Alocasia macrorrhiza [L.] G. Don) and soybean (Glycine max [L.]) were grown under high or low photon flux density (PFD) conditions to achieve a range of photosynthetic capacities and light-adaptation modes. The CO2 assimilation rate and in vivo linear electron transport rate (Jf) were determined over a range of PFDs and under saturating 1-s-duration lightflecks applied at a range of frequencies. At the same mean PFD, the assimilation rate and the Jf were lower under the lightfleck regimes than under constant light. The activation state of two, key enzymes of the photosynthetic carbon reduction cycle pathway, ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) and fructose-1,6-bisphosphatase, and the photosynthetic induction states (ISs) were also found to be lower under flashing as compared to continuous PFD. Under all conditions, the IS measured 120 s after an increase in PFD to constant and saturating values was highly correlated with the Rubisco activation state and stomatal conductances established in the light regime before the increase. Both the fructose-1,6-bisphosphatase and Rubisco activities established in a particular light regime were highly correlated with the mean Jf in that regime. The relationships between enzyme activation state and Jf and between IS and enzyme activation state were similar in soybean and Alocasia and were not affected either by growth-light regime, and hence photosynthetic capacity, or by flashing versus constant PFD. The common relationship between the linear Jf and the activation state of key enzymes suggests that electron transport may be the determinant of the signal regulating IS, at least to the extent that the IS is controlled by the activation state of key stromal enzymes.

  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: ABSTRACTA dynamic model of leaf photosynthesis for C3 plants has been developed for examination of the role of the dynamic properties of the photosynthetic apparatus in regulating CO2 assimilation in variable light regimes. The model is modified from the Farquhar-von Caemmerer-Berry model by explicitly including metabolite pools and the effects of light activation and deactivation of Calvin cycle enzymes. It is coupled to a dynamic stomatal conductance model, with the assimilation rate at any time being determined by the joint effects of the dynamic biochemical model and the stomatal conductance model on the intercellular CO2 pressure. When parametrized for each species, the model was shown to exhibit responses to step changes in photon flux density that agreed closely with the observed responses for both the understory plant Alocasia macrorrhiza and the crop plant Glycine max. Comparisons of measured and simulated photosynthesis under simulated light regimes having natural patterns of lightfleck frequencies and durations showed that the simulated total for Alocasia was within ±4% of the measured total assimilation, but that both were 12–50% less than the predictions from a steady–state solution of the model. Agreement was within ±10% for Glycine max, and only small differences were apparent between the dynamic and steady–state predictions. The model may therefore be parametrized for quite different species, and is shown to reflect more accurately the dynamics of photosynthesis than earlier dynamic models.
    Plant Cell and Environment 06/2008; 20(4):411 - 424. · 5.91 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The dynamic light environment and plant responses to it have been revealed by many studies in the last two decades. Asymmetric responses in stomatal conductance (gs) are commonly observed, and a relation with water use and carbon gain of plant has been suggested. This study focused on the temporal response of gs to fluctuating light intensity and its effect on gas exchange of a leaf. The temporal gs response of a leaf was approximated by a delay system that was characterized by a time constant (τ). The response is asymmetric if the time constant τ+ for increases in gs differs from the time constant τ− for decreases in gs, and the degree of asymmetry is measured by a parameter pτ=τ−/τ+. The mean output was derived under alternating input in the delay system. The range of pτ that strongly affected the mean output was determined. A strong dependency of mean output (gs) on pτ was observed at relatively large mean input (PFD) and pτ1 (rapid increase in gs). To confirm the effect of asymmetric gs response on gas exchange, dynamic gs and photosynthetic submodels previously proposed by other researchers were combined with an original submodel of leaf heat balance. The mean transpiration and photosynthetic rates (Ē and Ā) were calculated. The results showed that pτ in the gs submodel affected Ē more strongly than did Ā. This suggests that the asymmetry in the gs response controls the water use rather than the carbon gain under the conduction of fluctuating PFD.
    Ecological Modelling 01/2003; 164(1):65-82. · 2.33 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: High CO2 concentrations (HC) in air induce partial deactivation of ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBPCO, EC Under saturating irradiance, increase in [CO2] to 1 200 cm3 m-3 reduces the concentration of operating carboxylation centres by 20–30 %. At a further increase in [CO2], the activity remained on the same level. Under limiting irradiance, the lowest activity was reached at 600 cm3(CO2) m-3. The presence of oxygen diminished deactivation, but O2 failed to stimulate reactivation under high CO2. Conditions that favour oxygenation of ribulose-1,5-bisphosphate (RuBP) facilitated reactivation. Even HC did not act as an inhibitor. HC induces deactivation of RuBPCO by increasing the concentration of free reaction centres devoid of the substrate, which are more vulnerable to inhibition than the centres filled with substrates or products.
    Photosynthetica 01/2004; 42(2):283-290. · 1.01 Impact Factor

Full-text (2 Sources)

Available from
May 21, 2014