Model simulations link stomatal inhibition to impaired hydraulic conductance

Observations and model simulations link stomatal inhibition to impaired hydraulic conductance following ozone exposure in cotton

by Grantz D. A., Zhang X. J., Carlson T. (1999)

David A. Grantz, Xijie Zhang, Toby Carlson,

In Plant, Cell & Environment  22(10): 1201-1210 – DOI: 10.1046/j.1365-3040.1999.00486.x –


Ozone (O3) inhibits plant gas exchange and productivity. Vapour phase (gs) and liquid or hydraulic phase (K) conductances to water flux are often correlated as both change with environmental parameters. Exposure of cotton plants to tropospheric O3 reduces gs through reversible short‐term mechanisms and by irreversible long‐term disruption of biomass allocation to roots which reduces K. We hypothesize that chronic effects of O3 on gas exchange can be mediated by effects on K without a direct effect of O3 on gs or carbon assimilation (A). Experimental observations from diverse field and exposure chamber studies, and simulations with a model of mass and energy transport, support this hypothesis. O3 inhibition of K leads to realistic simulated diurnal courses of gs that reproduce observations at low ambient O3 concentration and maintain the positive correlation between midday gs and K observed experimentally at higher O3 concentrations. Effects mediated by reduced K may interact with more rapid responses of gs and A to yield the observed suite of oxidant impacts on vegetation. The model extends these physiological impacts to the extensive canopy scale. Simulated magnitudes and diurnal time courses of canopy‐scale fluxes of H2O and O3 match observations under low ambient concentrations of O3. With greater simulated concentrations of O3 during plant development, the model suggests potential reductions of canopy‐scale water fluxes and O3 deposition. This could represent a potentially unfavourable positive feedback on tropospheric O3 concentrations associated with biosphere–atmosphere exchange.

Ozone changes the linear relationship between photosynthesis and stomatal conductance

Ozone changes the linear relationship between photosynthesis and stomatal conductance and decreases water use efficiency in rice

by Masutomi Y., Kinose Y., Takimoto T., Yonekura T., Oue H., Kobayashi K.. (2019)

Yuji Masutomia, Yoshiyuki Kinoseb, Takahiro Takimotoc, Tetsushi Yonekurad, Hiroki Ouee, Kazuhiko Kobayashia

a Faculty of Agriculture, Ibaraki University, Japan

b Faculty of Life and Environmental Sciences, University of Yamanashi, Japan

c Institute for Agro-Environmental Sciences, NARO, Japan

d Center for Environmental Science in Saitama, Japan

e Faculty of Agriculture, Ehime University, Japan


In Science of The Total Environment  655: 1009-1016 – DOI:10.1016/j.scitotenv.2018.11.132 –


• Ozone significantly increased the intercept of the BWB relationship in rice.

• This change was found for a rice cultivar with the highest sensitivity to ozone.

• Increases in the intercept of the BWB relationship reflect a decreased water use efficiency.


Ozone is an important air pollutant that affects growth, transpiration, and water use efficiency (WUE) in plants. Integrated models of photosynthesis (An) and stomatal conductance (Gs) (An-Gs) are useful tools to consistently assess the impacts of ozone on plant growth, transpiration, and WUE. However, there is no information on how to incorporate the influence of ozone into An-Gs integrated models for crops. We focused on the Ball-Woodrow-Berry (BWB) relationship, which is a key equation in An-Gs integrated models, and aimed to address the following questions: (i) how does ozone change the BWB relationship for crops?; (ii) are there any difference in the changes in the BWB relationship among cultivars?, and (iii) how do the changes in the BWB relationship increase or decrease WUE for crops? We grew four rice cultivars in a field under ambient or Free-Air Concentration Enrichment (FACE) of ozone in China and measured An and Gs using a portable photosynthesis analyzer. We simulated WUE in individual leaves during the ripening period under different BWB relationships. The results showed that ozone significantly changed the BWB relationship only for the most sensitive cultivar, which showed an increase in the intercept of the BWB relationship under FACE conditions. These results imply that changes in the BWB relationship are related to the ozone sensitivity of the cultivar. Simulations of an An-Gs integrated model showed that increases in the intercept of the BWB relationship from 0.01 to 0.1 mol(H2O) m-2 s-1 indicated decreases in WUE by 22%. Since a reduction in WUE indicates increases in water demand per unit of crop growth, air pollution from ozone could be a critical issue in regions where agricultural water is limited, such as in rainfed paddy fields.

Effect of ozone on stomatal closure

Ozone. Effect on apparent photosynthesis, rate of transpiration, and stomatal closure in plants

by Hill A. C., Littlefield N. (1969)

A. Clyde Hill, Niel Littlefield,

Univ. of Utah, Salt Lake City


In Environ. Sci. Technol. 3(1): 52-56 –


The effect of soil water and atmospheric vapour pressure deficit on stomatal behaviour

The effect of soil water and atmospheric vapour pressure deficit on stomatal behaviour and photosynthesis in the oil palm

by Smith B. G. (1989)

In Journal of Experimental Botany 40: 647–651 –


The oil palm (Elaeis guineensis Jacq.) maintains a large leaf area throughout the year, but its productivity is limited by a low rate of dry matter production per unit leaf area. Stomatal closure, at times of low soil water availability and high atmospheric vapour pressure deficit, is an important factor limiting photosynthesis and hence dry matter production. In this paper, laboratory and field data are used to prepare a model of the relationships between net photosynthetic rate and stomatal conductance, and between stomatal conductance and environmental variables. Results show that high atmospheric vapour pressure deficits may limit production even in parts of the world where oil palms are not normally considered to suffer from water stress. The model can be used to design and evaluate irrigation systems, and to help quantify the potential value of oil palm genotypes with low stomatal sensitivity to either VPD or available soil water for use where irrigation is impractical.

Differing sensitivity of stomata to air humidity

Water Use Efficiency of Cassava. II. Differing sensitivity of stomata to air humidity in Cassava and other warm-climate species

by El-Sharkawy M. A., Cock J. H. & Held A. A. (1984)

Mabrouk A. El‐Sharkawy, James H. Cock, Alexander A. Held K.,


In Crop Science 24: 503–507 –

Measurements of CO2 and H20 exchange and the calculated leaf conductance of attached leaves in well‐watered plants were conducted over a range of leaf‐air vapor pressure differences (VPD) (1.0 to 4.0 kPa) to compare the response of cassava that of other warm‐climate species. Species tested were cassava (Manihot esculenta Crantz), andropogon (Andropogon gayanus Kunth), beans (Phaseolus vulgaris L.), siratro [Macroptilium atropurpureum (DC) urb], rice (Oryza sativa L.), eucalyptus (Eucalyptus deglupta Blume), amaranth weed (Amaranthus retroflexus L.) and grain sorghum [Sorghum bicolor (L) Moench]. Plants were grown in pots outdoors at the CIAT headquarters, Palmira, Colombia, South America. All except andropogon showed a decrease in leaf conductance with increase in VPD. The degree of stomatal sensitivity decreased as follows: cassava > siratro, amaranthus, eucalyptus, bean > sorghum, rice > andropogon. The greater sensitivity in cassava was associated with reduction in transpiration and stable leaf water potential (ψl) at large VPD. In other less sensitive species, transpiration increased and bulk leaf water potential decreased at large VPD. The response of cassava to changes in VPD resulted in higher water use efficiency (WUE = μmol CO2 uptake per mmol H2O loss) compared with other C3 species. This may contribute to the comparative advantage of cassava when grown under conditions of limited availability of water. The WUE of the C4 species (Sorghum, Andropogon, Amaranthus) were higher than those of the C3 species. This greater WUE of C4 species was attributed mainly to the higher photosynthetic rates of the C4 species rather than to a lower transpiration rate.

Effects of Clone and Irrigation on the Stomatal Conductance

Effects of Clone and Irrigation on the Stomatal Conductance and Photosynthetic Rate of Tea (Camellia sinensis)

by Smith B. G., Burgess P. J., Carr M. K. V. (1994)

  • (a1)†Unilever Plantations, Plant Breeding International (Cambridge), Maris Lane, Trumpington, Cambridge CB2 2LQ, England
  • (a2)‡Department of Agricultural Water Management, Silsoe College (Cranfield University), Silsoe, Bedford, MK45 4DT, England
  • (a3)§Ngwazi Tea Research Unit, Mufindi, c/o PO Box 4955, Dar-es-Salaam, Tanzania


In Experimental Agriculture 30(1): 1-16 – DOI:


Stomatal conductances (g) and photosynthetic rates (A) were monitored in six tea clones planted in a clone X irrigation experiment in the Southern Highlands of Tanzania. Measurements were made during the warm dry seasons of 1989 and 1990. There was no genotype X treatment interaction in the response in A or g of the various clones to irrigation. Irrigation increased A more than it increased g. Irrigation also increased the temperature optimum for photosynthesis and decreased photo-inhibition at high illuminance. Clones differed in g and A, and in the relationship between leaf temperature and A. The implications of these findings for clone selection are discussed.

Stomatal responses to vapour pressure deficit and drought

A rate equation model of stomatal responses to vapour pressure deficit and drought

by Eamus D., Shanahan S. (2002)

In BMC Ecol 2(8) –



Stomata respond to vapour pressure deficit (D) – when D increases, stomata begin to close. Closure is the result of a decline in guard cell turgor, but the link between D and turgor is poorly understood. We describe a model for stomatal responses to increasing D based upon cellular water relations. The model also incorporates impacts of increasing levels of water stress upon stomatal responses to increasing D.


The model successfully mimics the three phases of stomatal responses to D and also reproduces the impact of increasing plant water deficit upon stomatal responses to increasing D. As water stress developed, stomata regulated transpiration at ever decreasing values of D. Thus, stomatal sensitivity to D increased with increasing water stress. Predictions from the model concerning the impact of changes in cuticular transpiration upon stomatal responses to increasing D are shown to conform to experimental data.

Sensitivity analyses of stomatal responses to various parameters of the model show that leaf thickness, the fraction of leaf volume that is air-space, and the fraction of mesophyll cell wall in contact with air have little impact upon behaviour of the model. In contrast, changes in cuticular conductance and membrane hydraulic conductivity have significant impacts upon model behaviour.


Cuticular transpiration is an important feature of stomatal responses to D and is the cause of the 3 phase response to D. Feed-forward behaviour of stomata does not explain stomatal responses to D as feedback, involving water loss from guard cells, can explain these responses.