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.

Advertisements

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.

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.

Improvement of stomatal conductance models

Improvement of stomatal conductance models of rice under water saving irrigation treatment

Peng S., Pang G., Xu J., Zhang Z. (2009)

S. Peng, G. Pang, Junzeng Xu, Z. Zhang, 

in Nongye Gongcheng Xuebao/Transactions of the CSAE 25: 19–23. [in Chinese with English abstract] – 

https://www.researchgate.net/publication/288543709_Improvement_of_stomatal_conductance_models_of_rice_under_water_saving_irrigation_treatment

Abstract

In order to investigate the response relation model of stomatal conductance of rice leaves and related factors under water saving irrigation treatment, the field experiment was conducted in Kunshan experimental station of the State Key Laboratory of Hohai University in 2006.

According to the observed data, the response relation of different factors and stomatal conductance of rice was analyzed. Leaf-air temperature difference was introduced to improve the original models, and two types of representative models were compared as well.

The results indicated that the improved model taken into account of leaf-air temperature difference under the water saving irrigation condition had superior interpretive simulation ability than the original one.

The improved stomatal conductance model by Jarvis had better simulation results than the one improved by Leuning-Ball. The improved Jarvis stomatal conductance model is recommended under water saving irrigation treatment.

Leaf and stomata characteristics and drought tolerance indices

Leaf and stomata characteristics and tolerance of cowpea cultivars to drought stress based on drought tolerance indices under rainfed and irrigated conditions

by Peksen E., Peksen A. Gulumser A.. (2014)

Erkut Peksen, 1, Aysun Peksen, 2, Ali Gulumser, 1

1 Ondokuz Mayis University, Faculty of Agriculture, Department of Field Crop, Samsun, Turkey

2 Ondokuz Mayis University, Faculty of Agriculture, Department of Horticulture, Samsun, Turkey

https://www.researchgate.net/publication/260316270_Leaf_and_stomata_characteristics_and_tolerance_of_cowpea_cultivars_to_drought_stress_based_on_drought_tolerance_indices_under_rainfed_and_irrigated_conditions

===

in Int. J. Curr. Microbiol. App. Sci 3 (2): 626–634 – 

Abstract

In this study, leaf and stomata characteristics, and drought tolerance indices such as stress tolerance, mean productivity, geometric mean productivity, stress susceptibility index, stress index, stress tolerance index, harmonic mean, yield index and yield stability index were studied in cowpea (Vigna unguiculata (L.) Walp.) cultivars Karagoz-86 and Akkiz-86.

Experiments were setup based on completely randomized design (CRD) with factorial arrangement of the treatments with five replications under rainfed (non-watered) and irrigated (well-watered) conditions in 2005 and 2006 years.

Correlations among leaf characteristics (leaf number, leaf length, terminal leaflet length and width, petiolule length and leaf fresh weight), stomata characteristics (stoma number, stoma width and length on lower and upper epidermis) and seed yields of Karagoz-86 and Akkiz-86 under rainfed and irrigated conditions were determined.

Plant seed yield positively and significantly correlated with leaf number, leaf length, terminal leaflet width, terminal leaflet length, petiolule length, leaf fresh weight, plant height and pod number.

Based on drought tolerance indices, Karagoz-86 was found more tolerant to drought stress than Akkiz-86 and it could be recommended for rainfed condition.

Supplemental irrigation, particularly at flowering, pod setting and seed filling stage to improve plant growth and guarantee sufficient seed yield should be performed if it is possible.

Sap flux of co-occurring species and stomatal movements during seasonal soil drought

Sap flux of co-occurring species in a western subalpine forest during seasonal soil drought 

by Pataki D. E., Oren R., Smith W. K.(2000)

Diane E. Pataki, 1,3, Ram Oren, 1,  William K. Smith, 2,4

1 Nicholas School of the Environment, Duke University, Durham, North Carolina 27708 USA

2 Department of Botany, University of Wyoming, Laramie, Wyoming 82071 USA

===

in  Ecology 81: 2557–2566 – DOI: 10.2307/177474 – 

https://www.jstor.org/stable/177474?seq=1#page_scan_tab_contents

Abstract

Co-occurring species may utilize vastly different strategies to cope with limited water resources, particularly in areas subjected to predictable and recurring drought. While these physiological responses have commonly been measured at the leaf level, in small seedlings, and integrated in fluxes of whole stands or watersheds, sap flux measurements in large trees have become a useful tool for monitoring transpiration of individual canopies over long time periods.

In this study, sap flux (Js) was measured with constant heat sap flow gauges for co-occurring species which have been previously evaluated at the leaf level. Measurements were taken in a subalpine stand containing most of the dominant species of the central Rocky Mountains (Pinus contorta, Abies lasiocarpa, Populus tremuloides, and Pinus flexilis).

Daily Js values were parabolically related to daytime average atmospheric vapor pressure deficit (D) in all species, with a broad range of maximum Js values occurring between 1.2 and 1.8 kPa. Populus tremuloides had the greatest increases in Js with increasing D, while Pinus contorta showed the lowest Js.

A decrease in maximum Js was observed for all species later in the season when soil moisture declined from 0.35 to 0.24 m3/m3 at 0-45 cm. Late-season Js in A. lasiocarpa decreased 50% due to stomatal closure in response to the soil moisture deficit, regardless of daily D.

In contrast, the Pinus species were sensitive to D, showing larger late-season reductions in Js on high than on low D days. Populus tremuloides showed less sensitivity to soil moisture than the other species, with relatively high Js continuing late into the season and intermediate change in the response of Js to D with decreasing soil moisture.

Stand-level estimates of transpiration by plots dominated by Pinus contorta and A. lasiocarpa (2.6 ± 0.6 mm/d) were found to be similar to plots dominated by Populus tremuloides (2.7 ± 0.6 mm/d) despite the nearly fourfold higher leaf area indices for the conifers.