Light-dependent pH changes in leaves of C4 plants Comparison of the pH response to carbon dioxide and oxygen with that of C3 plants

Smallholder farmers in semi-arid areas depend on both cropping and livestock as the main sources of livelihoods. Rangeland productivity varies on both spatial and temporal scales and provides the major source of feed for livestock. Rangeland productivity is expected to decline with climate change thereby reducing livestock feed availability and consequently livelihoods that depend on livestock. This study was carried out to assess the impacts of climate change on rangeland productivity and consequently livestock population dynamics using a 30-year simulation modeling approach. The climate scenarios used in the simulations are built from the localized predictions by General Circulation Models (GCMs). The primary climate variables under consideration are rainfall (+/−7% change), carbon dioxide (CO2 up to 650 ppm) and temperature (+4 °C change). This was done by applying the SAVANNA ecosystem model which simulates rangeland processes and demographic responses of herbivores on a temporal and spatial scale using a weekly internal time step and monthly spatial and temporal outputs. The results show that rainfall levels of less than 600 mm/year have the largest negative effect on herbaceous biomass production. The amount of biomass from the woody layer does not change much during the year. The carbon dioxide (CO2) effects are more influential on the tree and shrub layers (C3 plants) than the herbaceous layer (C4 grasses). The CO2 effect was more dominant than the effects of rainfall and temperature. In the baseline simulations, the shrub plant layer increased significantly over 30 years while there is a three-fold increase in the woody plant layer (trees and shrubs) where biomass increased from a 1980 production to that of 2010. The biomass of the herbaceous layer was stable over the historical period (1980 to 2010) with values fluctuating between 200 and 400 g/m2. Grass green biomass has a variable distribution where most production occurred in the fields and cleared areas while lower levels of production were found in the forested areas. The spatial distribution of shrub green biomass was less directly linked to yearly rainfall. Shrub biomass was mostly found in forested areas, and it showed a steady increase in production. Cattle, donkey, and goat populations rose slowly from 1980 but the rise was disrupted by a dry period during the late 1980s to the early 1990s causing a decline in all populations primarily due to grass unavailability. The populations of cattle goats and donkeys started to rise again from 1995 onwards due to improvements in rainfall. Cattle and donkey populations were rising faster than that of goats while sheep population was not changing much for most of the simulation period, otherwise they declined significantly during the drought of 2002. Similar changes in simulated grass biomass (g/m2) were observed in almost all climate scenarios, except for the peak and low years. The livestock population simulation showed few variations in livestock population under all scenarios. The main conclusion from the study is that CO2 effects on rangeland productivity are much more dominant than the localized effects of rainfall and temperature. This has implications of favoring the growth of the tree and shrub layers over herbaceous layer, which meant that in the long run, the species that are able to use tree and shrub layers may be kept as a livelihood source as they will have a feed source.

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The end of life on Earth is not the end of the world: converging to an estimate of life span of the biosphere?

International Journal of Astrobiology ◽

10.1017/s1473550419000120 ◽

2019 ◽

Vol 19 (1) ◽

pp. 25-42 ◽

Cited By ~ 1

Author(s):

Fernando de Sousa Mello ◽

Amâncio César Santos Friaça

Keyword(s):

Partial Pressure ◽

Life Span ◽

Quantitative Agreement ◽

C4 Plants ◽

C3 Plants ◽

Ocean Mass ◽

The Future ◽

Geophysical Processes ◽

Red Giant ◽

Life On Earth

AbstractEnvironmental conditions have changed in the past of our planet but were not hostile enough to extinguish life. In the future, an aged Earth and a more luminous Sun may lead to harsh or even uninhabitable conditions for life. In order to estimate the life span of the biosphere we built a minimal model of the co-evolution of the geosphere, atmosphere and biosphere of our planet, taking into account temperature boundaries, CO2 partial pressure lower limits for C3 and C4 plants, and the presence of enough surface water. Our results indicate that the end of the biosphere will happen long before the Sun becomes a red giant, as the biosphere faces increasingly more difficult conditions in the future until its collapse due to high temperatures. The lower limit for CO2 partial pressure for C3 plants will be reached in 170(+ 320, − 110) Myr, followed by the C4 plants limit in 840(+ 270, − 100) Myr. The mean surface temperature will reach 373 K in 1.63(+ 0.14, − 0.05) Gyr, a point that would mark the extinction of the biosphere. Water loss due to internal geophysical processes will not be dramatic, implying almost no variation in the surface ocean mass and ocean depth for the next 1.5 billion years. Our predictions show qualitative convergence and some quantitative agreement with results found in the literature, but there is considerable scattering in the scale of hundreds of millions of years for all the criteria devised. Even considering these uncertainties, the end of the biosphere will hardly happen sooner than 1.5 Gyr.

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Quantum Yields of Photosystem II Electron Transport and Carbon Dioxide Fixation in C4 Plants

Functional Plant Biology ◽

10.1071/pp9900579 ◽

1990 ◽

Vol 17 (5) ◽

pp. 579 ◽

Cited By ~ 40

Author(s):

JP Krall ◽

GE Edwards

Keyword(s):

Carbon Dioxide ◽

Electron Transport ◽

Quantum Yield ◽

Photosystem Ii ◽

Malic Enzyme ◽

Co2 Fixation ◽

C4 Plants ◽

Quantum Yields ◽

Ps Ii ◽

Co2 Concentrations

The quantum yields of non-cyclic electron transport from photosystem II (determined from chlorophyll a fluorescence) and carbon dioxide assimilation were measured in vivo in representative species of the three subgroups of C4 plants (NADP-malic enzyme, NAD-malic enzyme and PEP-carboxykinase) over a series of intercellular CO2 concentrations (CI) at both 21% and 2% O2. The CO2 assimilation rate was independent of O2 concentration over the entire range of Ci (up to 500 μbar) in all three C4 subgroups. The quantum yield of PS II electron transport was similar, or only slightly greater, in 21% v. 2% O2 at all Ci values. In contrast, in the C3 species wheat there was a large O2 dependent increase in PS II quantum yield at low CO2, which reflects a high level of photorespiration. In the C4 plants, the relationship of the quantum yield of PS II electron transport to the quantum yield of CO2 fixation is linear suggesting that photochemical use of energy absorbed by PS II is tightly linked to CO2 fixation in C4 plants. This relationship is nearly identical in all three subgroups and may allow estimates of photosynthetic rates of C4 plants based on measurements of PS II photochemical efficiency. The results suggest that in C4 plants both the photoreduction of O2 and photorespiration are low, even at very limiting CO2 concentrations.

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Elevated Atmosphere Partial Pressure of CO2 and Plant Growth. III. Interactions Between Triticum aestivum (C3) and Echinochloa frumentacea (C4) During Growth in Mixed Culture Under Different CO2, N Nutrition and Irradiance Treatments, With Emphasis on Below-Ground Responses Estimated Using the δ13C Value of Root Biomass

Functional Plant Biology ◽

10.1071/pp9910137 ◽

1991 ◽

Vol 18 (2) ◽

pp. 137 ◽

Cited By ~ 40

Author(s):

SC Wong ◽

CB Osmond

Keyword(s):

Triticum Aestivum ◽

Mixed Culture ◽

Elevated Co2 ◽

Root Biomass ◽

Shoot Growth ◽

Mixed Cultures ◽

C4 Plants ◽

C3 Plants ◽

Δ13c Value ◽

Echinochloa Frumentacea

Wheat (Triticum aestivum L.), a C3 species, and Japanese millet (Echinochloa frumentacea Link), a C4 species, were grown in pots in monoculture and mixed culture (2 C3 : 1 C4 and 1 C3:2 C4) at two ambient partial pressures of CO2 (320 and 640 μbar), two photosynthetic photon flux densities (PPFDs) (daily maximum 2000 and 500 �mol m-2 s-1) and two levels of nitrogen nutrition (12 mM and 2 mM NO3-). Growth of shoots of both components in mixed culture was measured by physical separation, and the proportions of root biomass due to each component were calculated from δ13C value of total root biomass. In air (320 μbar CO2) at high PPFD and with high root zone-N, the shoot biomass of C3 and C4 components at the first harvest (28 days) was in proportion to the sowing ratio. However, by the second harvest (36 days) the C4 component predominated in both mixtures. Under the same conditions, but with low PPFD, C3 plants predominated at the first harvest but C4 plants had over- taken them by the time of the second harvest. Elevated atmospheric CO2 (640 μbar) stimulated shoot growth of Triticum in 15 of 16 treatment combinations and the stimulation was greatest in plants provided with low NO3-. Root growth of the C3 plants was generally stimulated by elevated CO2, but was only occasionally sensitive to the presence of C4 plants in mixed culture. However, growth of the C4 plants was often sensitive to the presence of C3 plants in mixed culture. In mixed cultures, elevated CO2 plants stimulated growth of C4 plants at high PPFD, high-N and in all low-N treatments but this was insufficient to offset a marked decline in shoot growth with increasing proportion of C3 plants in mixed cultures. The unexpected stimulation of growth of C4 plants by elevated CO2 was correlated with more negative δ13C values of C4 root biomass, suggesting a partial failure of the CO2 concentrating mechanism of C4 photosynthesis in Echinochloa under low-N. These experiments show that for these species nitrogen was more important than light or elevated pCO2 in determining the extent of competitive interactions in mixed culture.

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Mating of Helicoverpa armigera (Lepidoptera: Noctuidae) moths and their host plant origins as larvae within Australian cotton farming systems

Bulletin of Entomological Research ◽

10.1017/s0007485312000508 ◽

2012 ◽

Vol 103 (2) ◽

pp. 171-181 ◽

Cited By ~ 16

Author(s):

G.H. Baker ◽

C.R. Tann

Keyword(s):

Host Plant ◽

Helicoverpa Armigera ◽

Stable Carbon Isotopes ◽

Production Systems ◽

Farming Systems ◽

C4 Plants ◽

C3 Plants ◽

Bt Cotton ◽

Cotton Production ◽

Helicoverpa Armígera

AbstractTransgenic (Bt) cotton dominates Australian cotton production systems. It is grown to control feeding damage by lepidopteran pests such as Helicoverpa armigera. The possibility that these moths might become resistant to Bt remains a threat. Consequently, refuge crops (with no Bt) must be grown with Bt cotton to produce large numbers of Bt-susceptible moths to reduce the risk of resistance developing. A key assumption of the refuge strategy, that moths from different host plant origins mate at random, remains untested. During the period of the study reported here, refuge crops included pigeon pea, conventional cotton (C3 plants), sorghum or maize (C4 plants). To identify the relative contributions made by these (and perhaps other) C3 and C4 plants to populations of H. armigera in cotton landscapes, we measured stable carbon isotopes (δ13C) within individual moths captured in the field. Overall, 53% of the moths were of C4 origin. In addition, we demonstrated, by comparing the stable isotope signatures of mating pairs of moths, that mating is indeed random amongst moths of different plant origins (i.e. C3 and C4). Stable nitrogen isotope signatures (δ15N) were recorded to further discriminate amongst host plant origins (e.g. legumes from non-legumes), but such measurements proved generally unsuitable. Since 2010, maize and sorghum are no longer used as dedicated refuges in Australia. However, these plants remain very common crops in cotton production regions, so their roles as ‘unstructured’ refuges seem likely to be significant.

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Light-dependent pH changes in leaves of C3 plants

Planta ◽

10.1007/bf00208232 ◽

1991 ◽

Vol 184 (1) ◽

Cited By ~ 2

Author(s):

Zu-Hua Yin ◽

Katharina Siebke ◽

Ulrich Heber

Keyword(s):

C3 Plants ◽

Ph Changes

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Stable carbon isotopic composition of biomass burning emissions – implications for estimating the contribution of C3 and C4 plants

10.5194/acp-2021-897 ◽

2021 ◽

Author(s):

Roland Vernooij ◽

Ulrike Dusek ◽

Maria Elena Popa ◽

Peng Yao ◽

Anupam Shaikat ◽

...

Keyword(s):

Isotopic Composition ◽

Biomass Burning ◽

Field Experiments ◽

Combustion Products ◽

C4 Plants ◽

C3 Plants ◽

Stable Carbon ◽

Atmospheric Measurements ◽

C3 And C4 Plants ◽

Large Variability

Abstract. Landscape fires are a significant contributor to atmospheric burdens of greenhouse gases and aerosols. Although many studies have looked at biomass burning products and their fate in the atmosphere, estimating and tracing atmospheric pollution from landscape fires based on atmospheric measurements is challenging due to the large variability in fuel composition and burning conditions. Stable carbon isotopes in biomass burning (BB) emissions can be used to trace the contribution of C3 plants (e.g., trees or shrubs) and C4 plants (e.g. savanna grasses) to various combustion products. However, there are still many uncertainties regarding changes in isotopic composition (also known as fractionation) of the emitted carbon compared to the burnt fuel during the pyrolysis and combustion processes. To study BB isotope fractionation, we performed a series of laboratory fire experiments in which we burned pure C3 and C4 plants as well as mixtures of the two. Using isotope ratio mass spectrometry (IRMS), we measured stable carbon isotope signatures in the pre-fire fuels and post-fire residual char, as well as in the CO2, CO, CH4, organic carbon (OC), and elemental carbon (EC) emissions, which together constitute over 98 % of the post-fire carbon. Our laboratory tests indicated substantial isotopic fractionation in combustion products compared to the fuel, which varied between the measured fire products. CO2, EC and residual char were the most reliable tracers of the fuel 13C signature. CO in particular showed a distinct dependence on burning conditions; flaming emissions were enriched in 13C compared to smouldering combustion emissions. For CH4 and OC, the fractionation was opposite for C3 emissions (13C-enriched) and C4 emissions (13C-depleted). This indicates that while it is possible to distinguish between fires that were dominated by either C3 or C4 fuels using these tracers, it is more complicated to quantify their relative contribution to a mixed-fuel-fire based on the δ13C signature of emissions. Besides laboratory experiments, we sampled gases and carbonaceous aerosols from prescribed fires in the Niassa special Reserve (NSR) in Mozambique, using an unmanned aerial system (UAS)-mounted sampling set-up. We also provide a range of C3 : C4 contributions to the fuel and measured the fuel isotopic signatures. While both OC and EC were useful tracers of the C3 to C4 fuel ratio in mixed fires in the lab, we found particularly OC to be depleted compared to the calculated fuel signal in the field experiments. This suggests that either our fuel measurements were incomprehensive and underestimated the C3 : C4 ratio in the field, or that other processes caused this depletion. Although additional field measurements are needed, our results indicate that C3 vs C4 source ratio estimation is possible with most BB products, albeit with varying uncertainty ranges.

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The Kranz syndrome in the Eragrostideae (Chloridoideae, Poaceae) as indicated by carbon isotopic ratios*

Bothalia ◽

10.4102/abc.v15i3/4.1852 ◽

1984 ◽

Vol 15 (3/4) ◽

pp. 587-590

Author(s):

Hector O. Panarello ◽

Evangelina Sanchez

Keyword(s):

Mass Spectrometry ◽

C4 Photosynthesis ◽

Leaf Tissue ◽

C4 Plants ◽

C3 Plants ◽

Isotopic Ratios ◽

Carbon Isotope Ratios ◽

Carbon Isotopic ◽

Δ 13C ◽

Kranz Leaf Anatomy

13C/12C ratios are generally regarded as being very reliable indicators of C3 or C4 photosynthesis. These relative carbon isotope ratios are expressed as a negative δ 3C and fall into two distinct groups: Kranz (or C4) plants with δ between -9°/00 no and -18°/00 and non-Kranz (C3) plants with δ between -22°/00 and -280/00 no. In this paper, 29 taxa, representing 12 genera, of the tribe Eragrostideae were examined by mass spectrometry for their δ 13C in dried leaf tissue. All these taxa proved to be C4, plants with δ13C values ranging between -13,6°/oo and -10.9°/oo. These findings confirmed published leaf anatomical observations which showed that all the studied taxa had characteristic Kranz leaf anatomy.

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Light-dependent pH changes in leaves of C3 plants

Planta ◽

10.1007/bf00197120 ◽

1990 ◽

Vol 182 (2) ◽

Cited By ~ 2

Author(s):

Zu-Hua Yin ◽

Karl-Josef Dietz ◽

Ulrich Heber

Keyword(s):

C3 Plants ◽

Ph Changes

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Rhizodegradation of PAHs differentially altered by C3 and C4 plants

Scientific Reports ◽

10.1038/s41598-020-72844-4 ◽

2020 ◽

Vol 10 (1) ◽

Author(s):

Anithadevi Kenday Sivaram ◽

Suresh Ramraj Subashchandrabose ◽

Panneerselvan Logeshwaran ◽

Robin Lockington ◽

Ravi Naidu ◽

...

Keyword(s):

Bacterial Diversity ◽

Ribosomal Rna ◽

Bacterial Communities ◽

C4 Plants ◽

C3 Plants ◽

Good Resistance ◽

C3 And C4 Plants ◽

Incremental Change ◽

Polycyclic Aromatic ◽

Pahs Concentration

Abstract Pyrosequencing of 16S ribosomal RNA (rRNA) was employed to characterize bacterial communities colonizing the rhizosphere of plants with C3 and C4 photosynthetic pathways grown in soil contaminated with polycyclic aromatic hydrocarbons (PAHs) after 60 and 120 days. The results of this study exhibited a clear difference in bacterial diversity between the rhizosphere and non-rhizosphere samples and between the rhizospheres of the C3 and C4 plants after 120 days. In both C3 and C4 rhizospheres, an incremental change in PAHs degrading bacterial genera was observed in the 120th day samples compared to the 60th day ones. Among the PAHs degrading bacterial genera, Pseudomonas showed good resistance to PAHs in the 120th day rhizosphere of both C3 and C4 plants. Conversely, the genus Sphingomonas showed sensitivity to PAHs in the 120th day rhizosphere soils of C3 plants only. Also, a significant increase in the PAHs degrading genera was observed at 120th day in the C4 rhizosphere in comparison to the C3 rhizosphere, which was reflected in a reduced PAHs concentration measured in the soil remediated with C4 plants rather than C3 plants. These results suggest that the rhizoremediation of PAHs was primarily governed by the plant photosystems, which led to differences in root secretions that caused the variation in bacterial diversity seen in the rhizospheres. This study is the first report to demonstrate the greater effectiveness of C4 plants in enhancing the PAHs degrading bacterial community than C3 plants.

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