scholarly journals C4 Photosynthesis: Light-dependent CO2 Fixation by Mesophyll Cells, Protoplasts, and Protoplast Extracts of Digitaria sanguinalis

1975 ◽  
Vol 55 (5) ◽  
pp. 835-844 ◽  
Author(s):  
Steven C. Huber ◽  
Gerald E. Edwards
Keyword(s):  
Co2 Fixation ◽  
C4 Photosynthesis ◽  
Digitaria Sanguinalis ◽  
Mesophyll Cells

Quantum Yield of Photosystem II and Efficiency of CO2 Fixation in Flaveria (Asteraceae) Species under Varying Light and CO2

1991 ◽  
Vol 18 (4) ◽  
pp. 369 ◽  
Author(s):  
JP Krall ◽  
GE Edwards ◽  
MSB Ku
Keyword(s):  
Quantum Yield ◽  
Photosystem Ii ◽  
Co2 Fixation ◽  
C4 Photosynthesis ◽  
Co2 Assimilation ◽  
Quantum Yields ◽  
Progressive Development ◽  
Psii Activity ◽  
C3 And C4 Photosynthesis

The quantum yields of electron transport from photosystem II (PSII) (Φe, determined from chlorophyll a fluorescence), and CO2 assimilation (ΦCO2, photosynthetic rate/light intensity) were measured simultaneously in vivo with representative species of Flaveria which show a progression in development between C3 and C4 photosynthesis and in reduction of photorespiration. These were F. pringlei (C3), F. sonorensis (C3-C4, but lacking a C4 cycle), F. floridana (C3-C4, with partially functional C4 cycle), F. brownii (C4-like) and F. bidentis (C4). The level of PSII activity with varying CI under 210 mbar O2 was very similar in all species. However, the progressive development of C4 characteristics among the species produced an increased efficiency in utilisation of PSII derived energy for CO2 assimilation under 210 mbar O2, due to reduced photorespiratory losses at low CO2 levels. In all species, when photorespiration was limited by low O2 (20 mbar), there was a linear or near linear relationship between the quantum yield of PSII v. the quantum yield of CO2 fixation with varying intercellular levels of CO2 (Ci) indicating that CO2 fixation in this case is linked to PSII activity. When switching from 20 to 210 mbar O2 at atmosphere levels of CO2, there was a similar decrease in the efficiency in utilising PSII activity for CO2 assimilation at different light intensities, but the degree of sensitivity to O2 progressively decreased among the species concomitant with the development of C4 photosynthesis. These results may help explain why there is an advantage to evolution of C4 photosynthesis in environments where Ci becomes limiting.

scholarly journals The role of photorespiration during the evolution of C4 photosynthesis in the genus Flaveria

eLife ◽  
2014 ◽  
Vol 3 ◽  
Author(s):  
Julia Mallmann ◽  
David Heckmann ◽  
Andrea Bräutigam ◽  
Martin J Lercher ◽  
Andreas PM Weber ◽  
...  
Keyword(s):  
Nitrogen Metabolism ◽  
Carbon Fixation ◽  
C4 Photosynthesis ◽  
Mechanistic Model ◽  
Expression Patterns ◽  
Complex Trait ◽  
Mesophyll Cells ◽  
Remarkable Case ◽  
Balance Analysis ◽  
Biochemical Analyses

C4 photosynthesis represents a most remarkable case of convergent evolution of a complex trait, which includes the reprogramming of the expression patterns of thousands of genes. Anatomical, physiological, and phylogenetic and analyses as well as computational modeling indicate that the establishment of a photorespiratory carbon pump (termed C2 photosynthesis) is a prerequisite for the evolution of C4. However, a mechanistic model explaining the tight connection between the evolution of C4 and C2 photosynthesis is currently lacking. Here we address this question through comparative transcriptomic and biochemical analyses of closely related C3, C3–C4, and C4 species, combined with Flux Balance Analysis constrained through a mechanistic model of carbon fixation. We show that C2 photosynthesis creates a misbalance in nitrogen metabolism between bundle sheath and mesophyll cells. Rebalancing nitrogen metabolism requires anaplerotic reactions that resemble at least parts of a basic C4 cycle. Our findings thus show how C2 photosynthesis represents a pre-adaptation for the C4 system, where the evolution of the C2 system establishes important C4 components as a side effect.

Photosynthetic Mechanisms of Weeds in Taiwan

1993 ◽  
Vol 20 (6) ◽  
pp. 757 ◽  
Author(s):  
CH Lin ◽  
YS Tai ◽  
DJ Liu ◽  
MSB Ku
Keyword(s):  
Malic Enzyme ◽  
Co2 Fixation ◽  
C4 Photosynthesis ◽  
C3 Plants ◽  
C4 Species ◽  
On This Island ◽  
High Precipitation ◽  
Biochemical Analyses ◽  
Pep Carboxykinase ◽  
First Time

One hundred and one species (in 36 families) of weeds on cultivated land in Taiwan were investigated for the occurrence of Kranz leaf anatomy and activities of key enzymes of C4 photosynthesis to determine their photosynthetic mechanisms. Based on the anatomical and biochemical analyses, 75 species were found to possess the C3 and 26 species the C4 pathway of photosynthetic CO2 fixation. Among the 26 C4 species, 15 species are in Gramineae, 6 in Cyperaceae, 2 each in Euphorbiaceae and Amaranthaceae, and 1 in Portulacaceae. Two C4 species in the Gramineae, namely Digitaria radicosa (Presl) Miq. and Sporobolus fertilis (Steud.) Clayton, were recorded as C4 plants for the first time. The biochemical subdivisions of these C4 weeds were also determined. As in the natural C4 populations, the NADP-malic enzyme subtype of C4 photosynthesis dominates the list of C4 weeds on this island (62%), while the PEP carboxykinase subtype is relatively rare (12%). NAD-malic enzyme subtype has an intermediate representation (26%). The high proportion of weeds in Taiwan being C3 plants is noteworthy, and it may be accounted for by the high precipitation in this subtropical island.

scholarly journals Developmental Effects on Relative Use of PEPCK and NADP-ME Pathways of C4 Photosynthesis in Maize

2021 ◽  
Author(s):  
Jennifer J Arp ◽  
Shrikaar Kambhampati ◽  
Kevin Chu ◽  
Somnath Koley ◽  
Lauren M Jenkins ◽  
...  
Keyword(s):  
Enzyme Activity ◽  
Leaf Development ◽  
Phosphoenolpyruvate Carboxykinase ◽  
C4 Photosynthesis ◽  
Leaf Age ◽  
Bundle Sheath ◽  
Decarboxylase Activity ◽  
Mesophyll Cells ◽  
Source To Sink ◽  
Canopy Position

C4 photosynthesis is an adaptive photosynthetic pathway which concentrates CO2 around Rubisco in specialized bundle sheath cells to reduce photorespiration. Historically, the pathway has been characterized into three different subtypes based on the decarboxylase involved, although recent work has provided evidence that some plants can use multiple decarboxylases, with maize in particular using both the NADP-malic enzyme (NADP-ME) pathway and phosphoenolpyruvate carboxykinase (PEPCK) pathway. Parallel C4 pathways could be advantageous in balancing energy and reducing equivalents between bundle sheath and mesophyll cells, in decreasing the size of the metabolite gradients between cells and may better accommodate changing environmental conditions or source to sink demands on growth. The enzyme activity of C4 decarboxylases can fluctuate with different stages of leaf development, but it remains unclear if the pathway flexibility is an innate aspect of leaf development or an adaptation to the leaf microenvironment that is regulated by the plant. In this study, variation in the two C4 pathways in maize were characterized at nine plant ages throughout the life cycle. Two positions in the canopy were examined for variation in physiology, gene expression, metabolite concentration, and enzyme activity, with particular interest in asparagine as a potential regulator of C4 decarboxylase activity. Variation in C4 and C3 metabolism was observed for both leaf age and canopy position, reflecting the ability of C4 pathways to adapt to changing microenvironments.

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