scholarly journals Relationships between climate of origin and photosynthetic responses to an episodic heatwave depend on growth CO2 concentration for Eucalyptus camaldulensis var. camaldulensis

2017 ◽  
Vol 44 (11) ◽  
pp. 1053 ◽  
Author(s):  
Michael E. Loik ◽  
Víctor Resco de Dios ◽  
Renee Smith ◽  
David T. Tissue
Keyword(s):  
Elevated Co2 ◽  
Eucalyptus Camaldulensis ◽  
Co2 Concentration ◽  
Co2 Assimilation ◽  
Interactive Effects ◽  
Multiple Control ◽  
Air Temperatures ◽  
Eastern Australia ◽  
Photosynthetic Responses ◽  
Eucalyptus Camaldulensis Dehnh

Stressful episodic weather is likely to affect the C balance of trees as the climate changes, potentially altering survival. However, the role of elevated CO2 concentration ([CO2]) in tolerating off-season episodic extremes is not clear. We tested for interactive effects of elevated CO2 and springtime heat stress on photosynthesis for seven genotypes of Eucalyptus camaldulensis Dehnh. var. camaldulensis, representing its widespread distribution across south-eastern Australia. We grew clonal material under glasshouse conditions of ambient (aCO2; 400 parts per million (ppm)) or elevated (eCO2; 640 ppm) [CO2], and air temperatures of 25 : 17°C (day : night), and measured the electron transport rate in PSII (ETR), stomatal conductance to water vapour (gs) and net CO2 assimilation (A). Measurements were made before, during and after a four-day temperature excursion of 35 : 27°C. ETR and A were ~17% higher for plants grown in eCO2 than in aCO2. Photosynthesis remained stable for plants in eCO2 during the heatwave. Based on the effect size ratio (eCO2 : aCO2), gs and ETR were temporarily affected more by the heatwave than A. A reduction in ETR in eCO2 was the only lasting effect of the heatwave. There were no significant differences among genotypes. Correlations between photosynthesis and climate of origin differed for plants grown in aCO2 compared with eCO2, suggesting potential complex and multiple control points on photosynthesis.

scholarly journals Carboxylation Capacity Can Limit C3 Photosynthesis at Elevated CO2 throughout Diurnal Cycles

Plants ◽  
2021 ◽  
Vol 10 (12) ◽  
pp. 2603
Author(s):  
James Bunce
Keyword(s):  
Elevated Co2 ◽  
Carbon Fixation ◽  
Leaf Gas Exchange ◽  
Co2 Concentration ◽  
Ambient Air ◽  
Early Morning ◽  
C3 Plants ◽  
Lablab Purpureus ◽  
Diurnal Cycles ◽  
Air Temperatures

The response of carbon fixation in C3 plants to elevated CO2 is relatively larger when photosynthesis is limited by carboxylation capacity (VC) than when limited by electron transport (J). Recent experiments under controlled, steady-state conditions have shown that photosynthesis at elevated CO2 may be limited by VC even at limiting PPFD. These experiments were designed to test whether this also occurs in dynamic field environments. Leaf gas exchange was recorded every 5 min using two identical instruments both attached to the same leaf. The CO2 concentration in one instrument was controlled at 400 μmol mol−1 and one at 600 μmol mol−1. Leaves were exposed to ambient sunlight outdoors, and cuvette air temperatures tracked ambient outside air temperature. The water content of air in the leaf cuvettes was kept close to that of the ambient air. These measurements were conducted on multiple, mostly clear days for each of three species, Glycine max, Lablab purpureus, and Hemerocallis fulva. The results indicated that in all species, photosynthesis was limited by VC rather than J at both ambient and elevated CO2 both at high midday PPFDs and also at limiting PPFDs in the early morning and late afternoon. During brief reductions in PPFD due to midday clouds, photosynthesis became limited by J. The net result of the apparent deactivation of Rubisco at low PPFD was that the relative stimulation of diurnal carbon fixation at elevated CO2 was larger than would be predicted when assuming limitation of photosynthesis by J at low PPFD.

scholarly journals Carboxylation Capacity Can Limit Photosynthesis at Elevated CO2 throughout Diurnal Cycles

2021 ◽  
Author(s):  
James Bunce
Keyword(s):  
Elevated Co2 ◽  
Carbon Fixation ◽  
Leaf Gas Exchange ◽  
Co2 Concentration ◽  
Ambient Air ◽  
Early Morning ◽  
C3 Plants ◽  
Lablab Purpureus ◽  
Diurnal Cycles ◽  
Air Temperatures

The response of carbon fixation in C3 plants to elevated CO2 is relatively larger when photosynthesis is limited by carboxylation capacity (VC) than when limited by electron transport (J). Recent experiments under controlled, steady-state conditions have shown that photosynthesis at elevated CO2 may be limited by VC even at limiting PPFD. These experiments were designed to test whether this also occurs in dynamic field environments. Leaf gas exchange was recorded every 5 minutes using two identical instruments both attached to the same leaf. The CO2 concentration in one instrument was controlled at 400 mol mol-1 and one at 600 mol mol-1. Leaves were exposed to ambient sunlight outdoors, and cuvette air temperatures tracked ambient outside air temperature. The water content of air in the leaf cuvettes was kept close to that of the ambient air. These measurements were conducted on multiple, mostly clear days for each of three species, Glycine max, Lablab purpureus, and Hemerocallis fulva. The results indicated that in all species, photosynthesis was limited by VC rather than J at both ambient and elevated CO2 both at high midday PPFDs and also at limiting PPFDs in the early morning and late afternoon. During brief reductions in PPFD due to midday clouds, photosynthesis became limited by J, The net result of the apparent deactivation of Rubisco at low PPFD was that the relative stimulation of diurnal carbon fixation at elevated CO2 was larger than would be predicted when assuming limitation of photosynthesis by J at low PPFD.

Warming alters the positive impact of elevated CO2 concentration on cotton growth and physiology during soil water deficit

2017 ◽  
Vol 44 (2) ◽  
pp. 267 ◽  
Author(s):  
Katrina J. Broughton ◽  
Renee A. Smith ◽  
Remko A. Duursma ◽  
Daniel K. Y. Tan ◽  
Paxton Payton ◽  
...  
Keyword(s):  
Soil Water ◽  
Water Deficit ◽  
Elevated Co2 ◽  
Water Loss ◽  
Recovery Period ◽  
Co2 Concentration ◽  
Interactive Effects ◽  
Plant Water ◽  
Soil Water Deficit ◽  
Whole Plant

Alterations in climate factors such as rising CO2 concentration ([CO2]), warming and reduced precipitation may have significant impacts on plant physiology and growth. This research investigated the interactive effects of elevated [CO2], warming and soil water deficit on biomass production, leaf-level physiological responses and whole-plant water use efficiency (WUEP) in cotton (Gossypium hirsutum L.). Cotton was grown in the glasshouse under two [CO2] treatments (CA, 400 µL L–1; CE, 640 µL L–1) and two temperature treatments (TA, 28°C : 17°C day : night; TE, 32°C : 21°C day : night). Plants were subjected to two progressive water deficit cycles, with a 5-day recovery period between the water deficit periods. CE increased vegetative biomass and photosynthetic rates, and decreased stomatal conductance in TA; however, these responses to CE were not evident under TE. CE increased whole-plant water loss under TA, but increased WUEp, whereas increased whole-plant water loss in TE decreased WUEp regardless of atmospheric [CO2]. CE may provide some positive growth and physiological benefits to cotton at TA if sufficient water is available but CE will not mitigate the negative effects of rising temperature on cotton growth and physiology in future environments.

scholarly journals Physiological Plasticity of Green Gram Stomata to Photosynthesis Traits under Interactive Effects of Elevated CO2, Drought and Heat Stress

2021 ◽  
pp. 109-119
Author(s):  
J. Ranjani Priya ◽  
D. Vijayalakshmi ◽  
A. Vinitha ◽  
M. Raveendran ◽  
V. Babu Rajendra Prasad
Keyword(s):  
Gas Exchange ◽  
Elevated Co2 ◽  
Heat Waves ◽  
Co2 Concentration ◽  
Interactive Effects ◽  
Green Gram ◽  
Combined Stress ◽  
Gas Exchange Parameters ◽  
Randomized Design ◽  
Drought And Heat Stress

Heat waves and droughts are projected to become more widespread as a result of climate change. At the same time, CO2 levels are predicted to have doubled by 2100. The stomatal regulation and gas exchange characteristics were assessed in 25 days old plants of green gram (var Co 8) by exposing them to six different treatments namely, T1: a [CO2] + a T+ irrigation (100%), T2: a [CO2] + a T+ irrigation (50%), T3: a [CO2] + e T (40ºC) + irrigation (100%), T4: e [CO2] – 800 ppm + a T+ irrigation (100%), T5: a [CO2] + combined stress [e T (40ºC) + irrigation (50%) T6: e [CO2] – 800 ppm + combined stress [e T (40ºC) + irrigation (50%)]. The experiment was carried out using Completely Randomized Design (CRD) with three replications. All gas exchange parameters viz., ((photosynthesis rate, stomatal conductance, and transpiration rate) were determined before imposing stress and two weeks after imposing stress. Stomatal characters was examined two weeks after imposing stress. Elevated CO2 stress caused a reduction in stomatal frequency accompanied by larger stomatal size. The study revealed the positive effect of higher CO2 concentration on gas exchange traits of the C3 crops viz., green gram.

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