Article

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: 6.56). 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.

0 Bookmarks
 · 
56 Views
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The present study investigated changes in photosynthetic characteristics of Guazuma ulmifolia Lam. (early successional species) and Hymenaea courbaril L. (late successional species) grown in contrasting light conditions as a way of assessing photosynthetic plasticity. Early successional species typically inhabit gap environments being exposed to variability in multiple resources, hence it is expected that these species would show higher photosynthetic plasticity than late successional ones. In order to test this hypothesis, light and CO2 response curves and chlorophyll content (Chl) were measured in plants grown in high and low light environments. G. ulmifolia presented the highest amounts of both Chl a and b, especially in the low light, and both species presented higher Chl a than b in both light conditions. The Chl a/b ratio was higher in high light leaves of both species and greater in G. ulmifolia. Taken together, these results evidence the acclimation potential of both species, reflecting the capacity to modulate light harvesting complexes according to the light environment. However, G. ulmifolia showed evidence of higher photosynthetic plasticity, as indicated by the greater amplitude of variation on photosynthetic characteristics between environments shown by more significant shade adjusted parameters (SAC) and principal component analysis (PCA). Thus, the results obtained were coherent with the hypothesis that the early successional species G. ulmifolia exhibits higher photosynthetic plasticity than the late successional species H. courbaril.
    Brazilian journal of biology = Revista brasleira de biologia 02/2010; 70(1):75-83.
  • [Show abstract] [Hide abstract]
    ABSTRACT: The light environment in plant canopies is characterized by rapid fluctuations in photon flux density (PFD) because of the occurrence of sunflecks. These sunflecks can contribute most of the PFD available for photosynthesis and thus the mechanisms that control their utilization can have a significant impact on the carbon gain within canopies or in understories. When sunflecks are infrequent, their utilization is constrained by the induction requirement of the photosynthetic apparatus. The induction requirement has been shown to involve three separate factors consisting of an increase in the capacity for regeneration of ribulose bisphosphate that is important in the first 1–2 min after a light increase, the light activation of ribulose 1,5-bisphosphate carboxylase that occurs over the first 5–10 min of induction, and an increase in stomatal conductance. Under the conditions of multiple sunflecks occurring in varying succession characteristic of canopy light regimes, the induction state of a leaf is a function of the up and down regulation of these three factors. The induction state determines the readiness of a leaf to respond to a sunfleck in terms of the maximum assimilation rate that can be achieved during it. Post-lightfleck CO2 assimilation occurring because of the utilization of high-energy metabolite pools built up during the lightfleck can substantially enhance the utilization of short lightflecks. This buildup occurs because of a transient uncoupling of electron transport and carbon assimilation rates as 3-phosphoglyceric acid pools are reduced allowing for initially elevated electron transport rates during a lightfleck. Simulation modeling and measurements have shown that under natural sunfleck regimes in forest understories the induction state of leaves may limit daily assimilation by 10 to 25%. Post-lightfleck CO2 fixation, on the other hand, does not significantly enhance sunfleck use in this environment because the short sunflecks for which it is most important make little contribution to the available sunfleck PFD. Within crop canopies, where the contribution of short-duration sunflecks is much greater, simulation modeling indicates a more important role forpost-lightfleck CO2 fixation.
    07/2006: pages 321-346;
  • [Show abstract] [Hide abstract]
    ABSTRACT: A broad overview of the physiology and biochemistry of Rubisco is presented with a comparison of information obtained in vitro and in vivo. First a brief background to kinetic properties of Rubisco is given and Rubisco’s influence on photosynthetic metabolism is reviewed for C3, C4, CAM and C3-C4 species. The effect of environmental variables such as light and CO2 are considered for both short and longer term effects on the activity and abundance of Rubisco protein. Over the past few years experiments with transgenic plants with antisense RNA constructs to Rubisco, Rubisco activase and several of the PCR cycle enzymes have added new insights into Rubisco physiology. For example, transgenic tobacco with reduced amount of Rubisco has allowed the identification of environmental conditions where Rubisco exerts maximal control on photosynthesis. These plants have also been used to determine Rubisco kinetic constants in vivo. Transgenic plants with reduced amounts of Rubisco activase have been used to elucidate the role of activase in vivo.
    04/2006: pages 85-113;

Full-text (2 Sources)

View
17 Downloads
Available from
May 21, 2014