scholarly journals The Development of Crassulacean Acid Metabolism (CAM) Photosynthesis in Cotyledons of the C4 Species, Portulaca grandiflora (Portulacaceae)

Plants ◽  
2020 ◽  
Vol 9 (1) ◽  
pp. 55 ◽  
Author(s):  
Lonnie J. Guralnick ◽  
Kate E. Gilbert ◽  
Diana Denio ◽  
Nicholas Antico
Keyword(s):  
Enzyme Activity ◽  
Water Stress ◽  
Crassulacean Acid Metabolism ◽  
Acid Metabolism ◽  
Leaf Tissue ◽  
Fluorescence Analysis ◽  
Titratable Acidity ◽  
O2 Evolution ◽  
Portulaca Grandiflora ◽  
C4 Pathway

Portulaca grandiflora simultaneously utilizes both the C4 and Crassulacean acid metabolism (CAM) photosynthetic pathways. Our goal was to determine whether CAM developed and was functional simultaneously with the C4 pathway in cotyledons of P. grandiflora. We studied during development whether CAM would be induced with water stress by monitoring the enzyme activity, leaf structure, JO2 (rate of O2 evolution calculated by fluorescence analysis), and the changes in titratable acidity of 10 and 25 days old cotyledons. In the 10 days old cotyledons, C4 and CAM anatomy were evident within the leaf tissue. The cotyledons showed high titratable acid levels but a small CAM induction. In the 25 days old cotyledons, there was a significant acid fluctuation under 7 days of water stress. The overall enzyme activity was reduced in the 10 days old plants, while in the 25 days old plants CAM activity increased under water-stressed conditions. In addition to CAM, the research showed the presence of glycine decarboxylase in the CAM tissue. Thus, it appears both pathways develop simultaneously in the cotyledons but the CAM pathway, due to anatomical constraints, may be slower to develop than the C4 pathway. Cotyledons showed the ancestral Atriplicoid leaf anatomy, which leads to the question: Could a CAM cell be the precursor to the C4 pathway? Further study of this may lead to understanding into the evolution of C4 photosynthesis in the Portulaca.

Photosynthetic and anatomical characteristics in the C4–crassulacean acid metabolism-cycling plant Portulaca grandiflora

2002 ◽  
Vol 29 (6) ◽  
pp. 763 ◽  
Author(s):  
Lonnie J. Guralnick ◽  
Gerald Edwards ◽  
Maurice S. B. Ku ◽  
Brandon Hockema ◽  
Vince Franceschi
Keyword(s):  
Water Stress ◽  
Crassulacean Acid Metabolism ◽  
Carbon Fixation ◽  
Acid Metabolism ◽  
Water Storage ◽  
Diurnal Fluctuation ◽  
Carbon Gain ◽  
O2 Evolution ◽  
Storage Tissue ◽  
Portulaca Grandiflora

This paper originates from a presentation at the IIIrd International Congress on Crassulacean Acid Metabolism, Cape Tribulation, Queensland, Australia, August 2001. Portulaca grandiflora (Lind.) is a succulent species with C4 photosynthesis and crassulacean acid metabolism (CAM) cycling in leaves, and CAM-idling type photosynthesis in stems. We investigated the level and localization of carbon fixation enzymes and photosynthetic activity of leaves and stems of P. grandiflora under well-watered and drought conditions. As CAM activity increased during water stress, the leaf water-storage tissue collapsed, presumably transferring water to the bundle sheath and mesophyll cells, and so maintaining the C4 photosynthetic pathway. Tissue prints indicated an increase in phosphoenolpyruvate carboxylase (PEPC) in the water-storage tissue of leaves and the cortex of stems. Immunoblot analyses after 10 d of water stress showed that leaves had a slight decrease in the proteins of the C4-CAM pathway, while at the same time a new isoform of NADP-malic enzyme (NADP-ME) appeared. In contrast, the stem showed increases in proteins of the CAM pathway when water stressed. Under water stress, diurnal fluctuation in acidity in leaves was not accompanied by a net gain or loss of CO2 at night, and there was sustained, but decreased, fixation of CO2 during the day, characteristic of CAM cycling. High gross rates of O2 evolution were maintained during the day under water stress, suggesting induction of alternative electron sinks. With induced diurnal fluctuations in acidity in stems, there was no net carbon gain during the day or night. These results demonstrate, for the first time, that the stem of P. grandiflora is an inducible CAM-idling tissue. Our results also indicate that the C4 and CAM pathways operate independently of one another in P. grandiflora.

Degrees of crassulacean acid metabolism in tropical epiphytic and lithophytic ferns

1999 ◽  
Vol 26 (8) ◽  
pp. 749 ◽  
Author(s):  
Joseph A.M. Holtum ◽  
Klaus Winter
Keyword(s):  
Carbon Isotope ◽  
Crassulacean Acid Metabolism ◽  
Acid Metabolism ◽  
Dark Period ◽  
Titratable Acidity ◽  
Isotope Ratios ◽  
Light Period ◽  
Co2 Uptake ◽  
Carbon Isotope Ratios ◽  
Net Co2 Uptake

Crassulacean acid metabolism (CAM) was observed in three species of tropical ferns, the epiphytes Microsorium punctatum and Polypodium crassifolium and the lithophyte Platycerium veitchii. Polypodium crassifolium and P. veitchii exhibited characteristics of weak CAM. Although no net nocturnal CO2 uptake was observed, the presence of CAM was inferred from nocturnal increases in titratable acidity of 4.7 and 4.1 µequiv (g fr wt)–1 respectively, a reduction in the rates of net CO2 evolution during the first half of the dark period, and the presence of a CAM-like decrease in net CO2 uptake during the early light period. In M. punctatum net CO2 uptake during the first half of the dark period was accompanied by an increase in titratable acidity of 39.2 µequiv (g fr wt)–1 and a pronounced reduction in net CO2 uptake during the early light period. When water was withheld from P. crassifolium and M. punctatum, net CO2 uptake during the light was reduced markedly but there was no change in the extent or patterns of CO2 exhange in the dark. As a consequence, the proportion of carbon gained due to CO2 fixation in the dark increased from 2.8 and 10% to 63.5 and 49.3%, respectively (100% being net CO2 uptake during the light plus the estimated CO2 uptake during the dark). After 9 days without added water, dark CO2 uptake was responsible for the maintenance of a net 24 h carbon gain in P. crassifolium. Platycerium veitchii, P. crassifolium and M. punctatum exhibited carbon isotope ratios of between –25.9 and –22.6‰ indicating that carbon isotope ratios may not, by themselves, be sufficient for the identification of weak CAM. We suggest that CAM may be more prevalent in tropical epiphytic and lithophytic ferns than currently envisaged.

Crassulacean Acid Metabolism in Orchids under Water Stress

1982 ◽  
Vol 143 (3) ◽  
pp. 294-297 ◽  
Author(s):  
C. F. Fu ◽  
C. S. Hew
Keyword(s):  
Water Stress ◽  
Crassulacean Acid Metabolism ◽  
Acid Metabolism

scholarly journals Phosphoenolpyruvate carboxylase from pennywort (Umbilicus rupestris). Changes in properties after exposure to water stress

1984 ◽  
Vol 218 (2) ◽  
pp. 387-393 ◽  
Author(s):  
P P Daniel ◽  
J A Bryant ◽  
F I Woodward
Keyword(s):  
Water Stress ◽  
Phosphoenolpyruvate Carboxylase ◽  
Crassulacean Acid Metabolism ◽  
Acid Metabolism ◽  
Marked Decrease ◽  
Cam Plants ◽  
Allosteric Inhibitor ◽  
Allosteric Effector ◽  
Incomplete Form ◽  
C3 Photosynthesis

Umbilicus rupestris (pennywort) switches from C3 photosynthesis to an incomplete form of crassulacean acid metabolism (referred to as ‘CAM-idling’) when exposed to water stress (drought). This switch is accompanied by an increase in the activity of phosphoenolpyruvate carboxylase. This enzyme also shows several changes in properties, including a marked decrease in sensitivity to acid pH, a lower Km for phosphoenolpyruvate, very much decreased sensitivity to the allosteric inhibitor malate, and increased responsiveness to the allosteric effector glucose 6-phosphate. The Mr of the enzyme remains unchanged, at approx. 185 000. These changes in properties of phosphoenolpyruvate carboxylase are discussed in relation to the roles of the enzyme in C3 and in CAM plants.

Effect of Different CO2 Regimes on the Induction of Crassulacean Acid Metabolism in Mesembryanthemum crystallinum L

1979 ◽  
Vol 6 (6) ◽  
pp. 589 ◽  
Author(s):  
K Winter
Keyword(s):  
Water Stress ◽  
Phosphoenolpyruvate Carboxylase ◽  
Crassulacean Acid Metabolism ◽  
Acid Metabolism ◽  
High Salinity ◽  
Stomatal Closure ◽  
Initial Step ◽  
Mesembryanthemum Crystallinum ◽  
Initial Event ◽  
Response To Water

Induction of crassulacean acid metabolism (CAM) in Mesembryanthemum crystallinum in response to high salinity was studied in plants grown in different CO2 regimes to determine whether the induction of CAM could be controlled by CO2 supply in the light and dark; a possible consequence of stomatal closure in response to water stress. The activity of extractable phosphoenolpyruvate carboxylase (EC 4.1.1.31) and the nocturnal change in malate content were followed at frequent intervals after onset of the treatments. The results suggest that the initial event during the induction of CAM is a change in the biochemical apparatus, indicated by the activity of phosphoenolpyruvate carboxylase, which then leads to the day/night fluctuations of malate synthesis typical of CAM. This initial step is not controlled by the availability of CO2 in the light or dark.

scholarly journals Effect of Severe Water Stress on Aspects of Crassulacean Acid Metabolism in Xerosicyos

1993 ◽  
Vol 103 (4) ◽  
pp. 1089-1096 ◽  
Author(s):  
B. Bastide ◽  
D. Sipes ◽  
J. Hann ◽  
I. P. Ting
Keyword(s):  
Water Stress ◽  
Crassulacean Acid Metabolism ◽  
Acid Metabolism ◽  
Severe Water Stress
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