Whole-plant Chamber Research Articles

Ontogenetic changes in root and shoot respiration, fresh mass and surface area of Fagus crenata.

To date, studies on terrestrial plant ecology and evolution have focused primarily on the trade-off patterns in the allocation of metabolic production to roots and shoots in individual plants and the scaling of whole-plant respiration. However, few empirical studies have investigated the root : shoot ratio by considering scaling whole-plant respiration at various sizes throughout ontogeny. Here, using a whole-plant chamber system, we measured the respiration rates, fresh mass and surface area of entire roots and shoots from 377 Fagus crenata individuals, from germinating seeds to mature trees, collected from five different Japanese provenances. Non-linear regression analysis was performed for scaling of root and shoot respiration, fresh mass and surface area with body size. Whole-plant respiration increased rapidly in germinating seeds. In the seedling to mature tree size range, the scaling of whole-plant respiration to whole-plant fresh mass was expressed as a linear trend on the log-log coordinates (exponent slightly greater than 0.75). In the same body size range, root and shoot respiration vs. whole-plant fresh mass were modelled by upward-convex (exponent decreased from 2.35 to 0.638) and downward-convex trends (exponent increased from -0.918 to 0.864), respectively. The root fraction in whole-plant respiration, fresh mass and surface area shifted continuously throughout ontogeny, increasing in smaller seedlings during early growth stages and decreasing in larger trees. Our results suggest a gradual shift in allocation priorities of metabolic energy from roots in seedlings to shoots in mature trees, providing insights into how roots contribute to shoot and whole-plant growth during ontogeny. The models of root : shoot ratio in relation to whole-plant physiology could be applied in tree growth modelling, and in linking the different levels of ecological phenomena, from individuals to ecosystems.

Vapor pressure deficit constrains transpiration and photosynthesis in holm oak: A comparison of three methods during summer drought.

High rates of vapor pressure deficit (VPD) can severely decrease plant productivity by reducing stomatal conductance, which might be exacerbated during Mediterranean summers due to soil water deficit. In this study, we monitored the response of holm oak, the archetype of Mediterranean trees, to changes in VPD during a summer drought period to evaluate the effects and consequences on gas exchange of the two water stresses (atmospheric and soil). Measurements were performed on trees growing in an experimental plantation over two summers with moderate drought stress by using three different methods: at the leaf level with an infrared gas analyzer, using a whole-plant chamber for short-term monitoring at the tree level, and measuring the canopy temperature for long-term monitoring. The three methods provided negative relationships between leaf conductance and VPD but with discrepancies probably associated with the measurement scale. Overall, the results showed that atmospheric and soil water stress had an additive effect. Under well-watered conditions, an increase in VPD was partially compensated by a reduction in stomatal conductance, resulting in a slight increase in the transpiration rates. With soil water deficit, the response to VPD resulted in a further decrease in stomatal conductance, reducing transpiration as a water saving strategy. The decrease in conductance in response to VPD was transitory, recovering to initial values as soon as the VPD decreased, both under well-watered and drought conditions. Due to this high sensitivity to atmospheric drought, the maximum carbon gain rates of holm oak were restricted to a short environmental window, which might modulate its physiological performance and natural distribution.

Whole-Plant Water Use in Field Grown Grapevine: Seasonal and Environmental Effects on Water and Carbon Balance.

Water scarcity is a main challenge in vineyards sustainability in most of the grapevine areas now and even more in near future due to climatic change perspectives. In consequence, water use efficiency (WUE) measurements are of the highest interest to improve the sustainability of this crop. The vast majority of WUE measurements relays on measurements of leaf carbon and water fluxes at leaf-level. However, less data are available at the whole-plant level, and for the moment those data are not totally coincident with conclusions reached at leaf scale. In this study, we used whole-plant chambers able to enclose an entire plant of 12 years old to measure at the same time water and carbon fluxes under realistic field grown conditions. The main objectives were to identify the technical issues interfering the whole-plant measurements and track the environmental and other abiotic factors that can affect water and carbon balance, i.e., WUE at the whole-plant scale. To achieve those objectives, we measured whole-plant water and carbon fluxes in grapevine exposed to two different water regimes at three phenological stages [pea size (July), ripening (August), and harvest (September)]. In September, measurements were repeated under high CO2 to also check its effect at the whole-plant scale. The results indicate that water and carbon fluxes are well coordinated under both water availability treatments. Under drought conditions, both fluxes were drastically reduced, but surprisingly the estimated WUE resulted not improved but decreased, contrarily to what is shown at the leaf scale. The phenology (September) also strongly decreased both water and carbon fluxes when compared to measurements in July. We hypostatized that harvest load respiration rates could have an important weight on the whole-plant net carbon exchange (NCE). Finally, high CO2 measurements, after correction for leaks, indicated an increase of whole-plant NCE as well as increased whole-plant WUE, as expected. Several technical issues were identified, like 1/instability of [CO2] during the night period that prevent robust estimation of whole-plant respiration and 2/condensation during last night and sun-rise hours which may affect the estimation of daily plant transpiration.

Analysis of leaf wetting effects on gas exchanges of corn using a whole-plant chamber system

A whole-plant chamber system equipped with a transpiration sap flow meter was developed for measuring the transpiration rate even if leaves are wetted. A preliminary experiment in which dynamics of transpiration rate and/or evaporation rate of wetted and non-wetted plants were measured and compared with each other demonstrated the validity of the measurement system. The system was then used to analyse leaf wetting effects on gas exchange of corn under slight water stress conditions of soil (a volumetric soil water content of 9.7%). Leaf wetting decreased vapour pressure in leaves by decreasing leaf temperature but it increased vapour pressure in the air; therefore, vapour pressure difference between leaves and air, as a driving force of transpiration, was significantly lower in wetted plant. As a result, transpiration rate decreased by 44% and leaf conductance as an index of stomatal aperture was increased by leaf wetting. Such increasing leaf conductance due to leaf wetting increased the photosynthetic rate by 30% and therefore it improved water use efficiency (2.4 times). These results suggest that morning leaf wetting due to night time dew formation may have an advantage in crop production in semi-arid regions.

Using whole-plant chambers to estimate carbon and water fluxes in field-grown grapevines

There are limited studies available that have investigated the effects of different levels of water supply on the whole-plant gas exchange dynamics. The latter is related to the difficulty in measuring whole-canopy carbon fixation and water consumption, especially in field conditions. Whole-plant chambers can measure these fluxes, therefore the aims of this work were (i) to determine the relationship between whole-plant gas exchange compared to single leaf gas exchange; (ii) to validate whole-canopy chamber measurements using sap flow probes; (iii) to measure the effect of soil water availability on water use efficiency calculated from gas exchange measured using whole-plant chambers. For these purposes, an experiment was carried out during the 2014 season in an experimental vineyard using six-years-old plants of cv. Grenache. Two irrigation regimes were established, moderate irrigation (50 % ETo) and non-irrigation. Carbon fixation and transpiration were measured using whole-plant chambers at veraison and pre-harvest. Simultaneously, leaf gas exchange was measured at different canopy positions during the day in order to compare those measurements with the whole-plant chamber data. In parallel, sap flow measurements were continuously recorded using heat balance probes. Results showed that CO2 fixation measured at noon in sun exposed leaves oriented to the south presented the highest correlation coefficient with whole plant chamber data. Whole-plant transpiration measured with whole-plant chambers was slightly higher compared to the estimated from sap flow data in both irrigated and non-irrigated plants. In general intensive leaf-level measurements do not completely reflect the whole plant physiology, due to variability of leaf to leaf environmental conditions and plant regulation of gas exchange.

A whole-plant chamber system for parallel gas exchange measurements of Arabidopsis and other herbaceous species.

BackgroundPhotosynthetic assimilation of carbon is a defining feature of the plant kingdom. The fixation of large amounts of carbon dioxide supports the synthesis of carbohydrates, which make up the bulk of plant biomass. Exact measurements of carbon assimilation rates are therefore crucial due to their impact on the plants metabolism, growth and reproductive success. Commercially available single-leaf cuvettes allow the detailed analysis of many photosynthetic parameters, including gas exchange, of a selected leaf area. However, these cuvettes can be difficult to use with small herbaceous plants such as Arabidopsis thaliana or plants having delicate or textured leaves. Furthermore, data from single leaves can be difficult to scale-up for a plant shoot with a complex architecture and tissues in different physiological states. Therefore, we constructed a versatile system—EGES-1—to simultaneously measure gas exchange in the whole shoots of multiple individual plants. Our system was designed to be able record data continuously over several days.ResultsThe EGES-1 system yielded comparable measurements for eight plants for up to 6 days in stable, physiologically realistic conditions. The chambers seals have negligible permeability to carbon dioxide and the system is designed so as to detect any bulk-flow air leaks. We show that the system can be used to monitor plant responses to changing environmental conditions, such as changes in illumination or stress treatments, and to compare plants with phenotypically severe mutations. By incorporating interchangeable lids, the system could be used to measure photosynthetic gas exchange in several genera such as Arabidopsis, Nicotiana, Pisum, Lotus and Mesembryanthemum.ConclusionEGES-1 can be introduced into a variety of growth facilities and measure gas exchange in the shoots diverse plant species grown in different growth media. It is ideal for comparing photosynthetic carbon assimilation of wild-type and mutant plants and/or plants undergoing selected experimental treatments. The system can deliver valuable data for whole-plant growth studies and help understanding mutant phenotypes. Overall, the EGES-1 is complementary to the readily-available single leaf systems that focus more on the photosynthetic process in within the leaf lamina.Electronic supplementary materialThe online version of this article (doi:10.1186/s13007-015-0089-z) contains supplementary material, which is available to authorized users.

Analysing uncertainties in the calculation of fluxes using whole-plant chambers: random and systematic errors

Aims Gas exchange measurements on individual plants depend largely on chamber systems, and uncertainties and corrections in current flux calculation procedures require further assessment.

Differential Uptake of Mercury Vapor by Gramineous C3 and C4 Plants

The uptake of mercury vapor by six gramineous plant species was compared under uniform conditions using a whole-plant chamber and (203)Hg-labeled mercury at a low atmospheric concentration. Mean Hg uptake by leaves of the C(3) species oats (Avena sativa), barley (Hordeum vulgare), and wheat (Triticum aestivum) was 5 times greater than that by leaves of the C(4) species corn (Zea mays), sorghum (Sorghum bicolor), and crabgrass (Digitaria sanguinalis). Although there was a difference in resistances associated with vapor entry into the leaves, as shown by estimates of gas exchange, the differential uptake by C(3) and C(4) species was largely attributable to internal resistances to Hg vapor binding. The nature of the internal resistances and the site or sites of Hg vapor binding remain unspecified.

Uptake of Mercury Vapor by Wheat

Using a whole-plant chamber and (203)Hg-labeled mercury, a quantitative study was made of the effect of environmental parameters on the uptake, by wheat (Triticum aestivum), of metallic mercury vapor, an atmospheric pollutant. Factors were examined in relation to their influence on components of the gas-assimilation model, [Formula: see text]where U(Hg) is the rate of mercury uptake per unit leaf surface, C(a)' is the ambient mercury vapor concentration, C(l)' is the mercury concentration at immobilization sites within the plant (assumed to be zero), r(l.Hg) is the total leaf resistance to mercury vapor exchange, and r(m.hg) is a residual term to account for unexplained physical and biochemical resistances to mercury vapor uptake.Essentially all mercury vapor uptake was confined to the leaves. r(l.hg) was particularly influenced by illumination (0 to 12.8 klux), but unaffected by ambient temperature (17 to 33 C) and mercury vapor concentration (0 to 40 mug m(-3)). The principal limitation to mercury vapor uptake was r(m.hg), which was linearly related to leaf temperature, but unaffected by mercury vapor concentration and illumination, except for apparent high values in darkness.Knowing C(a)' and estimating r(l.hg) and r(m.hg) from experimental data, mercury vapor uptake by wheat in light was accurately predicted for several durations of exposure using the above model.