Effect of Cyclic Variations in Gas Exchange under Constant Environmental Conditions on the Ratio of Transpiration to Net Photosynthesis

Barrs, H. D.

doi:10.1111/j.1399-3054.1968.tb07318.x

Cited by 56 publications

(31 citation statements)

References 32 publications

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“…The effect of increasing leaf-water deficit on the residual or mesophyll resistance, rT,, is a matter of controversy. Our results in a companion report (10), the results by Boyer (3) using soybeans and corn, and work by others (1,15) indicate that the effect of leaf water deficit on rm, which includes the biochemical reaction at the site of fixation, is very small in the range of 0 to 20 bars leaf-water potential. Figure 2 shows the effect of RWC on rm and rT at the four levels of irradiance.…”

Section: Resultssupporting

confidence: 50%

Effects of Irradiance and Leaf Water Deficit on Net Carbon Dioxide Assimilation and Mesophyll and Transport Resistances

Mederski

Curry²,

Chen³

1975

Plant Physiol.

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Rate of net C02 assimilation by soil-grown soybean plants were studied over a range of relative leaf water contents at each of four levels of irradiance. There was a large interaction between light level and leaf water deficit on the rate of CO2 assimilation. The effect of leaf water deficit on assimilation became larger as irradiance increased. Both stomatal resistance to CO2 transport and mesophyll resistance to CO2 assimilation increased as leaf-water deficit increased. The increase in both resistance with changing leaf-water content was largest at high irradiance and became smaller as irradiance decreased. Relief of soil-moisture stress by watering induced large oscillations of C02 assimilation, stomatal resistance, and mesophyll resistance. The oscillation of the mesophyll resistance occurred in the absence of changes in relative water content and appeared to be related to oscillations in leaf temperaature. The observed increase in mesophyll resistance with decreasing leaf-water content under nonoscillative conditions may be caused by changes in leaf temperature rather than leaf water content.Subsequent to the experiments on the regulation of CO2 assimilation by stomata reported in a companion paper (10), we undertook studies, reported herein, of the interacting effect of leaf water deficit and light level on CO2 assimilation by the soybean plant. Under most field conditions, leaf water potential and light are the primary factors affecting stomatal resistance (14). Although reviews (7, 11) discuss the effects of single components of environment on stomatal behavior and CO2 uptake, there do not appear to be any reports on the interacting effects of light level and leaf water deficit on net CO2 assimilation.The results in our companion paper (10) and the work by others (3,4,15) dence by others (5, 12) that shows relatively large increases in mesophyll resistance with increasing leaf water deficit. Whether the conflicting evidence on the effect of leaf water deficit on mesophyll resistance is due to a difference on the reaction of various plant species, the methodology, or assumptions implicit in the determination of mesophyll resistance remains unanswered. In this paper the response of mesophyll and stomatal resistances to several levels of irradiance over a range of leaf water deficits are presented. MATERIALS AND METHODSThe general procedure consisted of enclosing a single soybean (Glycin7e max [L.] Merr.) leaflet, attached to the plant, in a Plexiglas chamber. Instrumentation permitted continuous, simultaneous determination of net CO2 assimilation (F), transpiration, leaf and air temperature, and the relative water content of the leaf. Four experimental runs were made at nonsaturating irradiance levels (I) of 0.098, 0.085, 0.059, and 0.041 ,ueinsteins cm-2 sec-' min-' in the wave length range of 400 to 700 nm. At each light level relative water content of the plant was allowed to decline from approximately 95 to 80% within the 7 to 8 hr required for a single run. The soil containing the plant was ...

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Section: Resultssupporting

confidence: 50%

Effects of Irradiance and Leaf Water Deficit on Net Carbon Dioxide Assimilation and Mesophyll and Transport Resistances

Mederski

Curry²,

Chen³

1975

Plant Physiol.

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“…The RWC indicates the water content of a given amount of leaf relative to its fully hydrated or fully turgid state and was determined using the following equation proposed by Barrs (1968)…”

Section: Relative Water Content (Rwc) and Electrolyte Leakage (El)mentioning

confidence: 99%

Silicon does not alleviate the adverse effects of drought stress in soybean plants

Ruppenthal

Zóz

Steiner

et al. 2016

SCA

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Beneficial effects of silicon (Si) in the plants growth under conditions of drought stress have been associated with to uptake and accumulation ability of element by different species. However, the effects of Si on soybean under water stress are still incipient and inconclusive. This study investigated the effect of Si application as a way to confer greater soybean tolerance to drought stress. The experiment was carried out in 20-L pots under greenhouse conditions. Treatments were arranged in a randomized block design in a 2 × 4 factorial: two water regimes (no stress or water stress) and four Si rates (0, 50, 100 and 200 mg kg -1 ). Soybean plants were grown until beginning flowering (R1) growth stage with soil moisture content near at the field capacity, and then it started the differentiation of treatments under drought by the suspension of water supply. Changes in relative water content (RWC) in leaf, electrolyte leakage from cells, peroxidase activity, plant nutrition and growth were measured after 7 days of drought stress and 3 days recovery. The RWC in soybean leaves decreased with Si rates in the soil. Silicon supply in soil with average content of this element, reduced dry matter production of soybean under well-irrigated conditions and caused no effect on dry matter under drought stress. The nitrogen uptake by soybean plants is reduced with the Si application under drought stress. The results indicated that the Si application stimulated the defense mechanisms of soybean plants, but was not sufficient to mitigate the negative effects of drought stress on the RWC and dry matter production. Key words: Glycine max. Water deficit. Electrolyte leakage from cells. Peroxidase activity. ResumoOs efeitos benéficos do silício (Si) no crescimento das plantas sob condições de déficit hídrico têm sido associados com a capacidade de absorção e acumulação deste elemento pelas diferentes espécies de plantas. No entanto, os efeitos de Si na cultura da soja em condições de déficit hídrico ainda são incipientes e inconclusivos. Este estudo investigou o efeito da aplicação de Si, como forma de conferir maior tolerância da soja ao estresse hídrico. O experimento foi conduzido em vasos de 20 L em condições de casa de vegetação. Os tratamentos foram dispostos em um delineamento em blocos casualizados, em esquema fatorial 2 × 4: dois regimes hídricos (sem ou com estresse hídrico) e quatro doses de Si (0, 50, 100 e 200 mg kg -1 ). As plantas de soja foram cultivadas até o início do florescimento (R1) com a teor

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“…The boundary layer resistance (ra), the stomatal resistance (r,), and the mesophyll resistance (rm) (13,14). The mesophyll resistance includes, besides a resistance to CO2 diffusion in the liquid phase, the photochemical and biochemical resistances which take place inside the chloroplast.It is known that increased plant water stress is followed by a decrease in the rate of photosynthesis (5, analyzing leaf temperature and CO2 and H20 exchange rates, that the decline in photosynthesis at reduced leaf water potentials was due primarily to an increase in stomatal diffusion resistance (2,5,13,29). In some circumstances an increase in mesophyll resistance to CO, diffusion in the liquid phase was implied as a factor controlling photosynthesis under stress conditions (15,24,28).…”

mentioning

confidence: 99%

Response of Carbon Dioxide Fixation to Water Stress

Plaut

Bravdo

1973

Plant Physiol.

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Application of water stress to isolated spinach (Spinacia oleracea) ehloroplasts by redutcion of the osmotic potentials of C02 fixation media below -6 to -8 bars resulted in decreased rates of fixation regardless of solute composition. A decrease in C02 fixation rate of isolated chloroplasts was also found when leaves were dehydrated in air prior to chloroplast isolation. An inverse response of C02 fixation to osmotic potential of the fixation medium was found with chloroplasts isolated from dehydrated leaves-namely, fixation rate was inhibited at -8 bars, compared with -16 or -24 bars.Low leaf water potentials were found to inhibit CO2 fixation of intact leaf discs to almost the same degree as they did C02 fixation by chloroplasts isolated from those leaves. C02 fixation by intact leaves was decreased by 50 and 80% when water potentials were reduced from -7.1 to -9.6 and from -7.1 to -17.6 bars, respectively. Transpiration was decreased by only 40 and 60%, under the same conditions. However, correction for the increase in leaf temperature indicated transpiration decreases of 57 and 80%, similar to the relative decreases in CO2 fixation.Despite the 4-fold increase in leaf resistance to C02 diffusion in the gas phase when the water potential of leaves was reduced from -6.5 to -14.0 bars, an additional increase of about 50% in mesophyll resistance was obtained. C02 concentration at compensation also increased when leaf water potential was reduced.The control of the CO2 pathway from the atmosphere to chloroplasts of higher plants is usually divided into three physical resistances arranged in series. The boundary layer resistance (ra), the stomatal resistance (r,), and the mesophyll resistance (rm) (13,14). The mesophyll resistance includes, besides a resistance to CO2 diffusion in the liquid phase, the photochemical and biochemical resistances which take place inside the chloroplast.It is known that increased plant water stress is followed by a decrease in the rate of photosynthesis (5, analyzing leaf temperature and CO2 and H20 exchange rates, that the decline in photosynthesis at reduced leaf water potentials was due primarily to an increase in stomatal diffusion resistance (2,5,13,29). In some circumstances an increase in mesophyll resistance to CO, diffusion in the liquid phase was implied as a factor controlling photosynthesis under stress conditions (15,24,28). Other investigators have shown a reduction in either photochemical or biochemical activities of the chloroplast itself when leaf water potentials were lowered (7,12,27). Recently, we have shown (22) that a decrease in osmotic potentials inhibited CO2 fixation of isolated chloroplasts even at a saturating concentration of CO2 at the chloroplast surface.Boyer (6) suggested that the rate of photosynthesis at leaf water potentials below -11 to -12 bars was limited by reduced photochemical activity of the leaves and not by CO2 diffusion rate or photosynthetic enzymes. The approach in the present work was to compare the response of CO2 fixation by i...

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Effect of Cyclic Variations in Gas Exchange under Constant Environmental Conditions on the Ratio of Transpiration to Net Photosynthesis

Cited by 56 publications

References 32 publications

Effects of Irradiance and Leaf Water Deficit on Net Carbon Dioxide Assimilation and Mesophyll and Transport Resistances

Effects of Irradiance and Leaf Water Deficit on Net Carbon Dioxide Assimilation and Mesophyll and Transport Resistances

Silicon does not alleviate the adverse effects of drought stress in soybean plants

Response of Carbon Dioxide Fixation to Water Stress

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