Responses to Ambient CO2 Concentrations by Sodium-Deficient C4 Plants

Whether the mesophyll conductance to CO2 movement (gm) within leaves of C3 plants changes with CO2 concentration remains a matter of debate, particularly at low CO2 concentrations. We tested for changes in gm over the range of sub-stomatal CO2 concentrations (Ci) for which Rubisco activity limited photosynthesis (A) in three plant species grown under the same conditions. Mesophyll conductance was estimated by three independent methods: the oxygen sensitivity of photosynthesis, variable J fluorescence combined with gas exchange, and the curvature of the Rubisco-limited A vs. Ci curve. The latter assay used a new method of rapidly obtaining data points at approximately every 3 μmol mol−1 for Rubisco-limited A vs. Ci curves, allowing separate estimates of curvature over limited Ci ranges. In two species, soybean and sunflower, no change in gm with Ci was detected using any of the three methods of estimating gm. In common bean measured under the same conditions as the other species, all three methods indicated large decreases in gm with increasing Ci. Therefore, change in gm with Ci in the Rubsico-limited region of A vs. Ci curves depended on the species, but not on the method of estimating gm.

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The Effect of CO2 Enrichment and Irradiance on the Growth, Morphology and Gas Exchange of a C3 (Panicum laxum) and a C4 (Panicum antidotale) Grass

Functional Plant Biology ◽

10.1071/pp96077_co ◽

1997 ◽

Vol 24 (3) ◽

pp. 407 ◽

Cited By ~ 3

Author(s):

Oula Ghannoum ◽

Susanne von Caemmerer ◽

Edward W. R. Barlow ◽

Jann P. Conroy

Keyword(s):

Gas Exchange ◽

Co2 Enrichment ◽

Fold Increase ◽

Dry Weight ◽

Co2 Concentration ◽

High Light ◽

High Co2 ◽

Low Co2 ◽

C4 Species ◽

C3 Species

The effect of CO2 enrichment and irradiance on the growth and gas exchange of two tropical grasses, Panicum laxum (C3) and Panicum antidotale (C4) were investigated. The two species were grown at either 350 (low) or 700 (high) µL L-1 CO2 concentration, under 40% (low) or 100% (high) of direct sunlight and supplied with ample water and nutrition. Elevated CO2 enhanced plant dry weight at both irradiances in the C3 species (1.41-fold and 1.71-fold increase at low and high light, respectively) but only at high light in the C4 species (1.28 fold increase). CO2 enrichment had no effect on the dry weight of P. antidotale, when stem development was suppressed by growth under artificial lighting. When measured at the CO2 concentration at which they were grown, assimilation rates were similar in the low and high CO2 grown plants, for both species. However, when measurements made at low CO2 were compared, CO2 assimilation rates of the high light, high CO2 grown C3 and C4 species were lower than those of their low CO2 grown counterparts. High CO2 strongly reduced the stomatal conductance of both species, while it affected the Rubisco content (30% decrease) of the high light C3 species only. This work shows clearly that C4 species can respond to CO2 enrichment under favourable growth conditions, and that acclimation to elevated CO2 in pasture grasses does not necessarily involve accumulation of non-structural carbohydrates or reduction of total N or soluble proteins in source leaves.

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Effect of Sodium Nutrition on Chlorophyll a/b Ratios in C4 Plants

Functional Plant Biology ◽

10.1071/pp9840325 ◽

1984 ◽

Vol 11 (4) ◽

pp. 325 ◽

Cited By ~ 1

Author(s):

M Johnston ◽

CPL Grof ◽

PF Brownell

Keyword(s):

Chlorophyll A ◽

Early Stage ◽

Chlorophyll Concentration ◽

C4 Plants ◽

Growth Responses ◽

Amaranthus Tricolor ◽

Sodium Deficiency ◽

Group I ◽

Chloris Gayana

Methods for the determination of chlorophyll were compared in Amaranthus tricolor, Kochia childsii and Chloris gayana. From sequential extraction data, 96% ethanol appeared to be more efficient than 80% acetone in extracting chlorophyll from these plants. The chlorophyll a/b ratio was significantly lower in sodium-deficient compared to normal C4 plants. Of the group I elements, only sodium, irrespective of the salt supplied to deficient cultures, restored the chlorophyll a/b ratios to the value observed in normal plants. The concentration of sodium required to increase the chlorophyll a/b ratio in leaves of sodium-deficient plants was similar to that required to bring about the growth responses. The increase of the chlorophyll a/b ratio occurred at an early stage during recovery from sodium deficiency preceding the increase in chlorophyll concentration and the growth response. It is therefore likely that the low chlorophyll a/b ratio may be intrinsically associated with the condition of sodium deficiency.

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The Effect of CO2 Enrichment and Irradiance on the Growth, Morphology and Gas Exchange of a C3 (Panicum laxum) and a C4 (Panicum antidotale) Grass

Functional Plant Biology ◽

10.1071/pp96077 ◽

1997 ◽

Vol 24 (2) ◽

pp. 227 ◽

Cited By ~ 50

Author(s):

Oula Ghannoum ◽

Susanne von Caemmerer ◽

Edward W. R. Barlow ◽

Jann P. Conroy

Keyword(s):

Gas Exchange ◽

Co2 Enrichment ◽

Fold Increase ◽

Dry Weight ◽

Co2 Concentration ◽

High Light ◽

High Co2 ◽

Low Co2 ◽

C4 Species ◽

C3 Species

The effect of CO2 enrichment and irradiance on the growth and gas exchange of two tropical grasses, Panicum laxum (C3) and Panicum antidotale (C4) were investigated. The two species were grown at either 350 (low) or 700 (high) µL L-1 CO2 concentration, under 40% (low) or 100% (high) of direct sunlight and supplied with ample water and nutrition. Elevated CO2 enhanced plant dry weight at both irradiances in the C3 species (1.41-fold and 1.71-fold increase at low and high light, respectively) but only at high light in the C4 species (1.28 fold increase). CO2 enrichment had no effect on the dry weight of P. antidotale, when stem development was suppressed by growth under artificial lighting. When measured at the CO2 concentration at which they were grown, assimilation rates were similar in the low and high CO2 grown plants, for both species. However, when measurements made at low CO2 were compared, CO2 assimilation rates of the high light, high CO2 grown C3 and C4 species were lower than those of their low CO2 grown counterparts. High CO2 strongly reduced the stomatal conductance of both species, while it affected the Rubisco content (30% decrease) of the high light C3 species only. This work shows clearly that C4 species can respond to CO2 enrichment under favourable growth conditions, and that acclimation to elevated CO2 in pasture grasses does not necessarily involve accumulation of non-structural carbohydrates or reduction of total N or soluble proteins in source leaves.

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An overview of how rubisco and carbohydrate metabolism may be regulated at elevated atmospheric [CO2] and temperature

Agricultural and Food Science ◽

10.23986/afsci.72745 ◽

1996 ◽

Vol 5 (3) ◽

pp. 261-270 ◽

Cited By ~ 16

Author(s):

George Bowes ◽

Joseph C. V. Vu ◽

Mian W. Hussain ◽

Arja H. Pennanen ◽

L. Hartwell Allen

Keyword(s):

Co2 Enrichment ◽

Co2 Concentration ◽

Sucrose Phosphate Synthase ◽

Atmospheric Co2 ◽

Elevated Atmospheric Co2 ◽

Low Co2 ◽

C3 Species ◽

Leaf Carbohydrates ◽

Effects Of Temperature ◽

Sucrose Phosphate

Although atmospheric CO2 concentration ([CO2]) has been up to 16-fold higher than at present, the past several million years have seen atypically low values. Thus, modern-day plants are adapted to cope with a low [CO2]/[O2] ratio. The present [CO2] does not saturate C3 photosynthesis, so its doubling produces an “efficiency effect”, but it is not always fully realized. Acclimation to high [CO2] during growth can down-regulate photosynthesis, presumably to optimize carbon acquisition and utilization. A primary factor in acclimation is a reduction in rubisco. Two crops, rice and soybean, were used to study this phenomenon. Rice photosynthesis and growth peaked at 500 μmol mol-1 , whereas soybean responded up to 990 μmol mol-1 . Rubisco concentration declined under CO2-enrichment and increasing temperatures, more so in rice than soybean. The rubisco kcat of rice was unaffected by growth [CO2] or temperature, but that from soybean was increased by both. In rice the capacity to handle carbohydrate, as measured by sucrose phosphate synthase activity was up-regulated by CO2 -enrichment, but not by temperature. Leaf carbohydrates were increased by [CO2], but decreased by higher temperatures, starch more so than sucrose. Even though C3 species differ in response to [CO2] and temperature, CO2 -enrichment can moderate adverse effects of temperature extremes.

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The Effect of Sodium Nutrition on the Pool Sizes of Intermediates of the C Photosynthetic Pathway

Functional Plant Biology ◽

10.1071/pp9880749 ◽

1988 ◽

Vol 15 (6) ◽

pp. 749 ◽

Cited By ~ 15

Author(s):

M Johnston ◽

CPL Grof ◽

PF Brownell

Keyword(s):

Direct Application ◽

Photosynthetic Pathway ◽

Growth Responses ◽

Amaranthus Tricolor ◽

Mesophyll Cells ◽

Sodium Deficiency ◽

C4 Species ◽

C3 Species ◽

Chloris Gayana ◽

Group 1

Changes in C4 pathway intermediates in response to sodium nutrition, consistent with the hypothesis that there is a limitation in the conversion of pyruvate to phosphoenolpyruvate (PEP) in the mesophyll cells in sodium-deficiency, were observed in the C4 species, Kochia childsii, Chloris gayana, Amaranthus edulis, Amaranthus tricolor and Atriplex spongiosa. In the C3 species Lycopersicon esculentum (tomato), no differences were observed when grown with or without added sodium. Of the group 1 elements, only sodium, irrespective of the salt supplied to deficient cultures, effected these changes in the C4 species. In the light, concentrations of aspartate, PEP and 3-phosphoglycerate (3-PGA) were lower and those of pyruvate and alanine were greater in sodium-deficient than normal plants. In the dark, concentrations of aspartate, pyruvate, alanine, PEP and 3-PGA were similar in sodium-deficient and normal plants. In the C4 species Atriplex spongiosa, the concentration of sodium required to bring about these changes corresponded to that required for growth responses. Rapid increases in the concentrations of malate, PEP and 3-PGA and decreases in pyruvate and alanine were observed following the direct application of sodium to leaves.

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Effects of nutrient (NPK) supply on sugar beet response to elevated atmospheric CO2

Netherlands Journal of Agricultural Science ◽

10.18174/njas.v46i2.488 ◽

1998 ◽

Vol 46 (2) ◽

pp. 157-170

Author(s):

J. Wolf

Keyword(s):

Total Yield ◽

Co2 Concentration ◽

Nutrient Supply ◽

Nutrient Concentrations ◽

Moderate Increase ◽

Elevated Atmospheric Co2 ◽

Doubled Co2 Concentration ◽

Increased Co2 Concentration ◽

Different Levels ◽

Ambient Co2

To study interactions between nutrient supply and increased CO2 concentration in sugarbeet, plants were grown in pots for 4 months at ambient and doubled CO2 concentration and different levels of N, P or K. Doubling of ambient CO2 resulted in a moderate increase in total yield (+24%) and beet yield (+34%), however this CO2 effect disappeared with increasing nutrient shortage (in particular nitrogen). CO2 doubling did not result in significant changes in the minimum nutrient concentrations in leaves and beets.

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