Will Plant Performance on Soils Prone to Drought or With High Mechanical Impedance to Root Penetration Be Improved Under Elevated Atmospheric CO2 Concentration

1992 ◽  
Vol 40 (5) ◽  
pp. 491 ◽  
Author(s):  
J Masle
Keyword(s):  
Stomatal Conductance ◽  
Elevated Co2 ◽  
Leaf Growth ◽  
Carbon Partitioning ◽  
Growth Patterns ◽  
Plant Performance ◽  
Root Penetration ◽  
Mechanical Resistance ◽  
Growth Responses ◽  
Root Cells

Plants growing on dry soils or on soils with high mechanical resistance to root penetration grow more slowly and exhibit lower stomatal conductance than those growing on moist and loose soils. In most situations in nature where edaphic stresses develop rather slowly (compared to stresses imposed in most pot experiments conducted under controlled conditions), photosynthesis is mainly reduced via stomatal effects rather than via changes in mesophyll capacity for photosynthesis. Elevated CO2 will induce an increase in the internal partial pressure of CO2, despite stomatal conductance being lowered even further. Photosynthesis will therefore be improved, and leaf turgor will be increased. It is widely thought that growth on dry or hard soils is not carbon limited because levels of soluble carbohydrates in the leaves and root cells are increased. It is shown in this paper that growth on soil with high mechanical resistance does respond to elevated CO2. However, this response is smaller than expected from the increase of carbon assimilation rate because: (a) carbon partitioning is altered so that supplementary carbohydrates are preferentially allocated to the roots; (b) leaf growth sensitivity to internal availability of sugars is lower than in plants growing on loose soils. These alterations of 'sink activity' and carbon partitioning are mediated by unknown signalling factor(s) induced in the roots. It is not known whether the root factors acting in droughted plants are of the same nature. In both droughted and impeded plants the interacting effects of these factors and of ambient CO2 levels are likely to result in improved transpiration efficiency. More experiments are needed in this area, however, especially to ascertain the relative contribution of changes in growth patterns versus changes in the patterns of water use. In conclusion, the importance of identifying the nature of the sink limitations induced by root signals is emphasised. It is a fundamental area of research to be developed not only for assessing growth responses to rising CO2 under edaphic stress, but likely also for reconciling conflicting responses of field-grown and pot-grown plants.

Elevated temperature and CO2 cause differential growth stimulation and drought survival responses in eucalypt species from contrasting habitats

2019 ◽  
Vol 39 (11) ◽  
pp. 1806-1820 ◽  
Author(s):  
Deborah M G Apgaua ◽  
David Y P Tng ◽  
Samantha J Forbes ◽  
Yoko F Ishida ◽  
Nara O Vogado ◽  
...  
Keyword(s):  
Elevated Temperature ◽  
Stomatal Conductance ◽  
Elevated Co2 ◽  
Elevated Temperatures ◽  
Interactive Effects ◽  
Plant Performance ◽  
Eucalyptus Species ◽  
Climate Change Scenarios ◽  
Differential Growth ◽  
Tropical Regions

Abstract Climate change scenarios predict increasing atmospheric CO2 concentrations ([CO2]), temperatures and droughts in tropical regions. Individually, the effects of these climate factors on plants are well established, whereas experiments on the interactive effects of a combination of factors are rare. Moreover, how these environmental factors will affect tree species along a wet to dry gradient (e.g., along tropical forest–savanna transitions) remains to be investigated. We hypothesized that under the simulated environmental conditions, plant growth, physiological performance and survivorship would vary in a manner consistent with the species’ positions of origin along this gradient. In a glasshouse experiment, we raised seedlings of three Eucalyptus species, each occurring naturally in a wet forest, savanna and forest–savanna ecotone, respectively. We evaluated the effect of drought, elevated temperature (4 °C above ambient glasshouse temperature of 22 °C) and elevated temperature in combination with elevated [CO2] (400 ppm [CO2] above ambient of 400 ppm), on seedling growth, survivorship and physiological responses (photosynthesis, stomatal conductance and water-use efficiency). Elevated temperature under ambient [CO2] had little effect on growth, biomass and plant performance of well-watered seedlings, but hastened mortality in drought-affected seedlings, affecting the forest and ecotone more strongly than the savanna species. In contrast, elevated [CO2] in combination with elevated temperatures delayed the appearance of drought stress symptoms and enhanced survivorship in drought-affected seedlings, with the savanna species surviving the longest, followed by the ecotone and forest species. Elevated [CO2] in combination with elevated temperatures also enhanced growth and biomass and photosynthesis in well-watered seedlings of all species, but modified shoot:root biomass partitioning and stomatal conductance differentially across species. Our study highlights the need for a better understand of the interactive effects of elevated [CO2], temperature and drought on plants and the potential to upscale these insights for understanding biome changes.

Growth responses to elevated CO2 in NADP-ME, NAD-ME and PCK C4 grasses and a C3 grass from South Africa

2001 ◽  
Vol 28 (1) ◽  
pp. 13 ◽  
Author(s):  
Stephanie J. E. Wand ◽  
Guy F. Midgley ◽  
William D. Stock
Keyword(s):  
Gas Exchange ◽  
Elevated Co2 ◽  
Nicotinamide Adenine Dinucleotide ◽  
Malic Enzyme ◽  
Leaf Growth ◽  
Growth Potential ◽  
Nicotinamide Adenine ◽  
Individual Species ◽  
C4 Grasses ◽  
Growth Responses

The potential use of C4 biochemical subtypes [nicotinamide adenine dinucleotide phosphate-malic enzyme (NADP-ME), nicotinamide adenine dinucleotide-malic enzyme (NAD-ME) and phosphoenolpyruvate carboxykinase (PCK)] as delimiters of plant functional types (PFTs) with distinct responses to rising atmospheric CO2 concentrations was investigated in South African grass species. Gas exchange and above-ground growth in ambient and elevated CO2 (360 and 660 µmol mol–1 , respectively) were determined in three NADP-ME species, two NAD-ME species, two PCK species and one C3 species, all excavated from the same field site. Plants were grown in open-top chambers in a greenhouse for 178 d. Net CO2 assimilation rates were only significantly increased in one NAD-ME species, but stomatal conductances decreased (in six out of eight species, by a mean of 46%) and instantaneous leaf water-use efficiency increased (in all species, by a mean of 89%) in elevated CO2. These responses did not differ between photosynthetic pathways. Parameters derived from photosynthetic CO2 and light response curves were also not differentially influenced by CO2 treatment between pathways. Gas exchange responses were generally poorly related to CO2 responsiveness. Significant increases in leaf growth and canopy leaf area in elevated CO2 were found in two NADP-ME species, whereas increases in non-leaf above-ground growth were measured in three species representing all three C4 subtypes. Growth responses in elevated CO2 were apparently not simply correlated with biochemical subtype characteristics, although the most significant responses (particularly at the leaf level) were found for the NADP-ME pathway. This result was more likely attributable to the significant positive correlation found between CO2 responsiveness of leaf growth and relative leaf regrowth potential of individual species, the latter being higher in the two responsive NADP-ME species. Therefore, categorisation of PFTs according to relative growth potential may be more appropriate for predictions of CO2 responsiveness in C4 grasses.

Canopy development and hydraulic function in Eucalyptus tereticornis grown in drought in CO2-enriched atmospheres

2007 ◽  
Vol 34 (12) ◽  
pp. 1137 ◽  
Author(s):  
Brian J. Atwell ◽  
Martin L. Henery ◽  
Gordon S. Rogers ◽  
Saman P. Seneweera ◽  
Marie Treadwell ◽  
...  
Keyword(s):  
Elevated Co2 ◽  
Shoot Growth ◽  
Co2 Enrichment ◽  
Atmospheric Co2 ◽  
Shoot Biomass ◽  
Eucalyptus Tereticornis ◽  
Growth Responses ◽  
Ambient Conditions ◽  
Long Distance ◽  
Pipe Model

We report on the relationship between growth, partitioning of shoot biomass and hydraulic development of Eucalyptus tereticornis Sm. grown in glasshouses for six months. Close coordination of stem vascular capacity and shoot architecture is vital for survival of eucalypts, especially as developing trees are increasingly subjected to spasmodic droughts and rising atmospheric CO2 levels. Trees were exposed to constant soil moisture deficits in 45 L pots (30–50% below field capacity), while atmospheric CO2 was raised to 700 μL CO2 L–1 in matched glasshouses using a hierarchical, multi-factorial design. Enrichment with CO2 stimulated shoot growth rates for 12–15 weeks in well-watered trees but after six months of CO2 enrichment, shoot biomasses were not significantly heavier (30% stimulation) in ambient conditions. By contrast, constant drought arrested shoot growth after 20 weeks under ambient conditions, whereas elevated CO2 sustained growth in drought and ultimately doubled the shoot biomass relative to ambient conditions. These growth responses were achieved through an enhancement of lateral branching up to 8-fold due to CO2 enrichment. In spite of larger transpiring canopies, CO2 enrichment also improved the daytime water status of leaves of droughted trees. Stem xylem development was highly regulated, with vessels per unit area and cross sectional area of xylem vessels in stems correlated inversely across all treatments. Furthermore, vessel numbers related to the numbers of leaves on lateral branches, broadly supporting predictions arising from Pipe Model Theory that the area of conducting tissue should correlate with leaf area. Diminished water use of trees in drought coincided with a population of narrower xylem vessels, constraining hydraulic capacity of stems. Commensurate with the positive effects of elevated CO2 on growth, development and leaf water relations of droughted trees, the capacity for long-distance water transport also increased.

scholarly journals Differential Growth Responses of Wheat Seedlings to Elevated CO2

2018 ◽  
Vol 10 (3) ◽  
pp. 400-409 ◽  
Author(s):  
Hamid Reza ESHGHIZADEH ◽  
Morteza ZAHEDI ◽  
Samaneh MOHAMMADI
Keyword(s):  
Leaf Area ◽  
Plant Height ◽  
Elevated Co2 ◽  
Co2 Concentration ◽  
Tolerance Index ◽  
Dry Matter Accumulation ◽  
Wheat Cultivars ◽  
Growth Responses ◽  
Differential Growth ◽  
Wheat Seedlings

Intraspecific variations in wheat growth responses to elevated CO2 was evaluated using 20 Iranian bread wheat (Triticum aestivum L.) cultivars. The plants were grown in the modified Hoagland nutrient solution at a greenhouse until 35 days of age using two levels of CO2 (~380 and 700 µmol mol–1). The shoot and root dry weights of the wheat cultivars exhibited average enhancements of 17% and 36%, respectively, under elevated CO2. This increase was associated with higher levels of chlorophyll a (25%), chlorophyll b (21%), carotenoid (30%), leaf area (54%) and plant height (49.9%). The leaf area (r = 0.69**), shoot N content (r = 0.62**), plant height (r = 0.60**) and root volume (r = 0.53*) were found to have important roles in dry matter accumulation of tested wheat cultivars under elevated CO2 concentration. However, responses to elevated CO2 were considerably cultivar-dependent. Based on the stress susceptibility index (SSI) and stress tolerance index (STI), the wheat cultivars exhibiting the best response to elevated CO2 content were ‘Sistan’, ‘Navid’, ‘Shiraz’, ‘Sepahan’ and ‘Bahar’, while the ones with poor responses were ‘Omid’, ‘Marun’, ‘Sorkhtokhm’ and ‘Tajan’. The findings from the present experiment showed significant variation among the Iranian wheat cultivars in terms of their responses to elevated air CO2, providing the opportunity to select the most efficient ones for breeding purposes.

CO2 × Nitrogen Interaction on Seedling Growth of Four Species of Eucalypt.

1992 ◽  
Vol 40 (5) ◽  
pp. 457 ◽  
Author(s):  
SC Wong ◽  
PE Kriedemann ◽  
GD Farquhar
Keyword(s):  
Leaf Area ◽  
Elevated Co2 ◽  
Eucalyptus Camaldulensis ◽  
Fold Increase ◽  
Wide Distribution ◽  
Growth Responses ◽  
Seedling Vigour ◽  
Co2 Effects ◽  
Whole Plant ◽  
Large Trees

Four eucalypt species were selected to represent two ecologically disparate groups which would be expected to contrast in seedling vigour and in the nature of growth responses to CO2 × nitrogen supply. Eucalyptus camaldulensis and E. cypellocarpa were taken as examples of fast-growing species with a wide distribution, that develop into large trees. By contrast, E. pauciflora and E. pulverulenta become smaller trees, and show a more limited distribution. Seedlings were established in pots (5 L) of a loamy soil and supplied with nutrient solution containing either 1.2 or 6.0 mM NO3- in both ambient (33 Pa) and CO2-enriched (66 Pa) greenhouses. Analysis of growth response to treatments (2 × 2 factorial) was based on destructive harvest of plants sampled on four occasions over 84 days for E. carnaldulensis and E. cypellocarpa, and 100 days for E. pulverulenta and E. pauciflora. A positive CO2 × N interaction on plant dry mass and leaf area was expressed in all species throughout the study period. In E. carnaldulensis and E. cypellocarpa, plant mass was doubled by high N at 33 Pa CO2, compared with a three to four-fold increase at 66 Pa to reach 34g by final harvest. In E. pulverulenta and E. pauciflora, slower growth resulted in about 50% less mass at a given age, but relative increases due to CO2 and N were of a similar order. A distinction can be made between N and CO2 effects on growth processes as follows. When trees were grown on low N, elevated CO2 increased nitrogen-use efficiency (NUE) at both leaf and whole plant levels. On high N, leaf NUE was increased in E. camaldulensis and E. cypellocarpa, but decreased in E. pulverulenta and E. pauciflora. Whole plant NUE showed no consistent response to elevated CO2 when plants were supplied high N. Net assimilation rate (NAR) was increased by elevated CO2 in all species on either N treatment. Moreover, high N increased NAR under either CO2 treatment in all species. There was a positive N × CO2 interaction on NAR in E. carnaldulensis and E. cypellocarpa, but not in E. pulverulenta and E. pauciflora. Growth indices for E. carnaldulensis and E. cypellocarpa species, and especially E. carnaldulensis, generally exceeded those for E. pulverulenta and E. pauciflora in terms of NAR, leaf NUE, N-enhancement of CO2 effects on leaf area and biomass, and non-structural carbohydrate content of foliage.

High vapour pressure deficit and low soil water availability enhance shoot growth responses of a C4 grass (Panicum coloratum cv. Bambatsi) to CO2 enrichment

1998 ◽  
Vol 25 (3) ◽  
pp. 287 ◽  
Author(s):  
Saman P. Seneweera ◽  
Oula Ghannoum ◽  
Jann Conroy
Keyword(s):  
Soil Water ◽  
Elevated Co2 ◽  
Vapour Pressure ◽  
Shoot Growth ◽  
Vapour Pressure Deficit ◽  
C4 Grasses ◽  
Growth Responses ◽  
High Co2 ◽  
C4 Grass ◽  
Shoot Mass

The hypothesis that shoot growth responses of C4 grasses to elevated CO2 are dependent on shoot water relations was tested using a C4 grass, Panicum coloratum (NAD-ME subtype). Plants were grown for 35 days at CO2 concentrations of 350 or 1000 µL CO2 L-1. Shoot water relations were altered by growing plants in soil which was brought daily to 65, 80 or 100% field capacity (FC) and by maintaining the vapour pressure deficit (VPD) at 0.9 or 2.1 kPa. At 350 µL CO2 L-1, high VPD and lower soil water content depressed shoot dry mass, which declined in parallel at each VPD with decreasing soil water content. The growth depression at high VPD was associated with increased shoot transpiration, whereas at low soil water, leaf water potential was reduced. Elevated CO2 ameliorated the impact of both stresses by decreasing transpiration rates and raising leaf water potential. Consequently, high CO2 approximately doubled shoot mass and leaf length at a VPD of 2.1 kPa and soil water contents of 65 and 80% FC but had no effect on unstressed plants. Water use efficiency was enhanced by elevated CO2 under conditions of stress but this was primarily due to increases in shoot mass. High CO2 had a greater effect on leaf growth parameters than on stem mass. Elevated CO2 increased specific leaf area and leaf area ratio, the latter at high VPD only. We conclude that high CO2 increases shoot growth of C4 grasses by ameliorating the effects of stress induced by either high VPD or low soil moisture. Since these factors limit growth of field-grown C4 grasses, it is likely that their biomass will be enhanced by rising atmospheric CO2 concentrations.

Elevated CO2 alleviates the impact of drought on barley improving water status by lowering stomatal conductance and delaying its effects on photosynthesis

2007 ◽  
Vol 59 (3) ◽  
pp. 252-263 ◽  
Author(s):  
Anabel Robredo ◽  
Usue Pérez-López ◽  
Hector Sainz de la Maza ◽  
Begoña González-Moro ◽  
Maite Lacuesta ◽  
...  
Keyword(s):  
Stomatal Conductance ◽  
Elevated Co2 ◽  
Water Status ◽  
The Impact

scholarly journals Environmental controls over methanol emission from leaves

2007 ◽  
Vol 4 (4) ◽  
pp. 2593-2640 ◽  
Author(s):  
P. Harley ◽  
J. Greenberg ◽  
Ü. Niinemets ◽  
A. Guenther
Keyword(s):  
Stomatal Conductance ◽  
Leaf Growth ◽  
Dry Mass ◽  
Leaf Temperature ◽  
Photon Flux ◽  
Photon Flux Density ◽  
Emission Model ◽  
Production Term ◽  
Methanol Production ◽  
Environmental Controls

Abstract. Methanol is found throughout the troposphere, with average concentrations second only to methane among atmospheric hydrocarbons. Proposed global methanol budgets are highly uncertain, but all agree that at least 60% of the total source arises from the terrestrial biosphere and primary emissions from plants. However, the magnitude of these emissions is also highly uncertain, and the environmental factors which control them require further elucidation. Using a temperature-controlled leaf enclosure, we measured methanol emissions from leaves of six plant species by proton transfer reaction mass spectrometry, with simultaneous measurements of leaf evapotranspiration and stomatal conductance. Rates of emission at 30°C varied from 0.3 to 38 μg g (dry mass)−1 h−1, with higher rates measured on young leaves, consistent with the production of methanol via pectin demethylation in expanding foliage. On average, emissions increased by a factor of 2.4 for each 10°C increase in leaf temperature. At constant temperature, emissions were also correlated with co-varying incident photosynthetic photon flux density and rates of stomatal conductance. The data were analyzed using the emission model developed by Niinemets and Reichstein (2003a, b), with the incorporation of a methanol production term that increased exponentially with temperature. It was concluded that control of emissions, during daytime, was shared by leaf temperature and stomatal conductance, although rates of production may also vary diurnally in response to variations in leaf growth rate in expanding leaves. The model, which generally provided reasonable simulations of the measured data during the day, significantly overestimated emissions on two sets of measurements made through the night, suggesting that production rates of methanol were reduced at night, perhaps because leaf growth was reduced or possibly through a direct effect of light on production. Although the short-term dynamics of methanol emissions can be successfully modeled only if stomatal conductance and compound solubility are taken into account, emissions on longer time scales will be determined by rates of methanol production, controls over which remain to be investigated.

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