An overview of the cellular and molecular mechanisms underlying ABA-evoked signaling events in stomata

Figure 1. The sequence of measurable early ABA-signaling
events in guard cells. Black boxes indicate the
beginning and duration of an event. ROS, reactive oxygen
species.

Early ABA signaling events in guard cells

by Pei Z. M., Kuchitsu K. (2005)

  • Zhen-Ming Pei, Department of Biology, Duke University, Durham, USA
  • Kazuyuki Kuchitsu,Department of Applied Biological Science, and Genome and Drug Research Center, Tokyo University of Science, Noda, Japan

===

in Journal of Plant Growth Regulation 24: 296–307 – DOI: 10.1007/s00344-005-0095-x – 

http://www.esalq.usp.br/lepse/imgs/conteudo_thumb/Early-ABA-Signaling-Events-in-Guard-Cells.pdf

Figure 2. A model for the early ABA-signaling events in
guard cells. Abscisic acid is perceived by an unknown
receptor (AAR), which triggers [Ca2+]i increases via H2O2-
activated Ca2+ influx channels (ICa) or Ca2+ release from
internal stores. The elevated [Ca2+]i induces further H2O2
production via stimulating NADPH oxidases, leading to a
positive feedback of [Ca2+]i increases. Both S-type and Ftype
anion channels (CLC) are activated by elevated
[Ca2+]i, resulting in anion efflux and depolarization of the
membrane potential. The depolarized membrane potential
promotes K+ efflux via K+ outward channels (Kout)
and inhibits K+ influx from K+ inward channels (Kin).
Meanwhile, K+ influx via Kin is inhibited by elevated
[Ca2+]i. The efflux of cations and anions reduces the solute
concentration in guard cells, and thus leads to water
efflux and stomatal closing.

Abstract

The plant hormone abscisic acid (ABA) regulates a wide variety of plant physiological and developmental processes, particularly responses to environmental stress, such as drought.

In response to water deficiency, plants redistribute foliar ABA and/or upregulate ABA synthesis in roots, leading to roughly a 30-fold increase in ABA concentration in the apoplast of stomatal guard cells. The elevated ABA triggers a chain of events in guard cells, causing stomatal closure and thus preventing water loss.

Although the molecular nature of ABA receptor(s) remains unknown, considerable progress in the identification and characterization of its downstream signaling elements has been made by using combined physiological, biochemical, biophysical, molecular, and genetic approaches.

The measurable events associated with ABA-induced stomatal closure in guard cells include, sequentially, the production of reactive oxygen species (ROS), increases in cytosolic free Ca2+ levels ([Ca2+]i), activation of anion channels, membrane potential depolarization, cytosolic alkalinization, inhibition of K+ influx channels, and promotion of K+efflux channels.

This review provides an overview of the cellular and molecular mechanisms underlying these ABA-evoked signaling events, with particular emphasis on how ABA triggers an “electronic circuitry” involving these ionic components.

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Stomatal conductance under varying atmospheric and soil water conditions

Canopy conductance of Pinus taeda, Liquidambar styraciflua and Quercus phellos under varying atmospheric and soil water conditions 

by Pataki D. E., Oren R., Katul G., Sigmon J. T. (1998)

School of the Environment, Duke University, Durham, NC 22708, USA.

in Tree Physiology 18: 307–315 – PMID: 12651370 – 

https://www.ess.uci.edu/~dpataki/reprints/18-307.pdf

Summary

Sap flow, and atmospheric and soil water data were collected in closed-top chambers under conditions of high soil water potential for saplings of Liquidambar styraciflua L., Quercus phellos L. and Pinus taeda L., three co-occurring species in the southeastern USA.

Responses of canopy stomatal conductance (g(t)) to water stress induced by high atmospheric water vapor demand or transpiration rate were evaluated at two temporal scales. On a diurnal scale, the ratio of canopy stomatal conductance to maximum conductance (g(t)/g(t,max)) was related to vapor pressure deficit (D), and transpiration rate per unit leaf area (E(l)). High D or E(l) caused large reductions in g(t)/g(t,max) in L. styraciflua and P. taeda.

The response of g(t)/g(t,max) to E(l) was light dependent in L. styraciflua, with higher g(t)/g(t,max) on sunny days than on cloudy days. In both L. styraciflua and Q. phellos, g(t)/g(t,max) decreased linearly with increasing D (indicative of a feed-forward mechanism of stomatal control), whereas g(t)/g(t,max) of P. taeda declined linearly with increasing E(l) (indicative of a feedback mechanism of stomatal control).

Longer-term responses to depletion of soil water were observed as reductions in mean midday g(t)/g(t,max), but the reductions did not differ significantly between species. Thus, species that employ contrasting methods of stomatal control may show similar responses to soil water depletion in the long term.

Stomata in Tilia sp. (lime tree)

Lower epidermis of lime tree (Tilia)

https://commons.wikimedia.org/wiki/Category:Microscopic_images_of_leaves_-epidermis_with_stomata#/media/File:Plant_leaf_epidermis(251_16)Lower_epidermis_of_lime_tree(Tilia).jpg

Photo Google Wikimedia Commons. 

Optical microscopy technique:Differential interference contrast (Nomarski)

Magnification: 1200x (for picture width 26 cm ~ A4 format).

Size of this preview: 800 × 512 pixels. – Original file ‎(3,752 × 2,401 pixels, file size: 1.74 MB, MIME type: image/jpeg).

Plant leaf epidermis (255 17) Lower epidermis of lime tree (Tilia).jpg

https://commons.wikimedia.org/wiki/File:Plant_leaf_epidermis_(255_17)Lower_epidermis_of_lime_tree(Tilia).jpg

This image comes from the archive of Josef Reischig and is part of the 384 pictures kindly donated by the authorship heirs under CC BY SA 3.0 license as a part of Wikimedia Czech Republic‘s GLAM initiative.  

Hidden categories: 

11 March 2014

Responses of sap flux and stomatal conductance to stepwise reductions in leaf area

Responses of sap flux and stomatal conductance of Pinus taeda L. trees to stepwise reductions in leaf area

by Pataki D. E., Oren R., Phillips N. (1998)

D. E. PATAKI, R. OREN, G. KATUL , J. SIGMON,

School of the Environment, Duke University, Durham, NC 22708, USA

===

in J. Exp. Bot. 49: 871–878 – 

https://www.ncbi.nlm.nih.gov/pubmed/12651370

Abstract

Sap flow, and atmospheric and soil water data were collected in closed-top chambers under conditions of high soil water potential for saplings of Liquidambar styraciflua L., Quercus phellos L. and Pinus taeda L., three co-occurring species in the southeastern USA. Responses of canopy stomatal conductance (g(t)) to water stress induced by high atmospheric water vapor demand or transpiration rate were evaluated at two temporal scales.

On a diurnal scale, the ratio of canopy stomatal conductance to maximum conductance (g(t)/g(t,max)) was related to vapor pressure deficit (D), and transpiration rate per unit leaf area (E(l)). High D or E(l) caused large reductions in g(t)/g(t,max) in L. styraciflua and P. taeda.

The response of g(t)/g(t,max) to E(l) was light dependent in L. styraciflua, with higher g(t)/g(t,max) on sunny days than on cloudy days. In both L. styraciflua and Q. phellos, g(t)/g(t,max) decreased linearly with increasing D (indicative of a feed-forward mechanism of stomatal control), whereas g(t)/g(t,max) of P. taeda declined linearly with increasing E(l) (indicative of a feedback mechanism of stomatal control).

Longer-term responses to depletion of soil water were observed as reductions in mean midday g(t)/g(t,max), but the reductions did not differ significantly between species.

Thus, species that employ contrasting methods of stomatal control may show similar responses to soil water depletion in the long term

The postulate that ion channels adopted stomatal guard cell‐specific functions after the divergence of bryophytes

On the origins of osmotically‐driven stomatal movements 

Sussmilch F. C., Roelfsema M. R. G., Hedrich R. (2018)

Frances C. Sussmilch, M. Rob G. Roelfsema, Rainer Hedrich,

Institute for Molecular Plant Physiology and Biophysics, University of Würzburg, Würzburg, Germany

===

in New Phytologist – published online and citable  – https://doi.org/10.1111/nph.15593 – 

https://nph.onlinelibrary.wiley.com/doi/abs/10.1111/nph.15593?af=R

Summary

Stomatal pores with aperture that can be adjusted by changes in guard cell turgor have facilitated plant success in dry environments.

We explore their evolutionary origins, considering recent findings from bryophytes. Unlike vascular plant stomata, which close to prevent water loss, bryophyte stomata become locked open to promote spore desiccation.

We find that the families of ion channels, known to control stomatal movements in angiosperms, are ancient and represented across extant land plants. However, while angiosperm guard cells express specific ion channel genes, none are specifically expressed in stomata‐bearing moss tissues.

Given the evolutionary shift in stomatal function from promotion to prevention of water loss, we postulate that ion channels adopted guard cell‐specific functions after the divergence of bryophytes.

Stomata in Tulipa (Liliaceae)

Phoro Google Wikimedia Commons – This image comes from the archive of Josef Reischig and is part of the 384 pictures kindly donated by the authorship heirs under CC BY SA 3.0 license as a part of Wikimedia Czech Republic‘s GLAM initiative. – Tulip leaf epidermis. – 3,749 × 2,399 (2.54 MB)

Optical microscopy technique:Differential interference contrast (Nomarski)

Magnification: 600x (for picture width 26 cm ~ A4 format).

11 March 2014 –3,751 × 2,401 (1.42 MB) – VicuñaUploader 1.20
Josef Reischig

Stomata in Lilium (Liliaceae)

Photo Google Wikimedia Commons – Photomicrograph of a Lilium leaf with stoma. A=Guard cell, B=Nucleus. Scale=0.1mm. – Source : Jon Houseman and Matthew Ford – 29 September 2014 – Author : Jon Houseman –Original file ‎(1,200 × 886 pixels, file size: 208 KB, MIME type: image/jpeg) – 1,200 × 886 (208 KB)