Effect of auxins on the modulation of stomatal opening, mediated through the activity of the plasma-membrane H+-ATPase.

 

 

Characterization of the plasma-membrane H+-ATPase from Vicia faba guard cells. Modulation by extracellular factors and seasonal changes.

by Lohse G., Hedrich R. (1992)

Screen Shot 2018-05-24 at 12.08.29

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in Planta 166: 206–214 –

Google Scholar – 

https://www.jstor.org/stable/23381682?seq=1#page_scan_tab_contents

Abstract

Stomatal movement is controlled by external and internal signals such as light, phytohormones or cytoplasmic Ca2+.
Using Vicia faba L., we have studied the dose-dependent effect of auxins on the modulation of stomatal opening, mediated through the activity of the plasma-membrane H+-ATPase. The patch-clamp technique was used to elucidate the electrical properties of the H+-ATPase as effected by growth regulators and seasonal changes. The solute composition of cytoplasmic and extracellular media was selected to record pump currents directly with high resolution. Proton currents through the ATPase were characterized by a voltage-dependent increase in amplitude, positive to the resting potential, reaching a plateau at more depolarized values.
Upon changes in extracellular pH, the resting potential of the cell shifted with a non-Nernst potential response (±21 mV), indicating the contribution of a depolarizing ionic conductance other than protons to the permeability of the plasma membrane. The use of selective inhibitors enabled us to identify the currents superimposing the H+-pump as carried by Ca2+.
Auxin-stimulation of this electroenzyme resulted in a rise in the outwardly directed H+ current and membrane hyperpolarization, indicating that modulation of the ATPase by the hormone may precede salt accumulation as well as volume and turgor increase.
Annual cycles in pump activity (1.5—3.8 μA·cm-2) were expressed by a minimum in pump current during January and February. Resting potentials of up to -260mV and plasma-membrane surface area, on the other hand, did not exhibit seasonal changes. The pump activity per unit surface area was approximately 2- to 3-fold higher in guard cells than in mesophyll cells and thus correlates with their physiological demands.

 

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Modeling stomatal responses to environment

 

 

Modeling stomatal responses to environment in Macadamia integrifolia 

by Lloyd J. (1991)

Jonathan_Lloyd8
Jonathan Lloyd, Imperial College London, UK

===

in Australian Journal of Plant Physiology 18: 649660 – DOI – 10.1071/PP9910649 –

CrossRef

http://www.publish.csiro.au/fp/PP9910649

Abstract

Gas exchange measurements were made of photosynthetic and stomatal responses of Macadamia integrifolia under controlled conditions. Test leaves were subjected to a range of temperatures, humidities and photon irradiances. When stomatal responses to humidity were plotted as a function of vapour mol fraction difference (D) a similar curvilinear response was observed at all temperatures and at photon irradiances of 200 and 1500 μmol quanta m-2 s-1. By contrast, when expressed as a function of relative humidity, different slopes in the humidity response were observed, and at high photon irradiances, stomatal conductances (gs) appeared to have an optimum temperature below 15ºC. Simple equations to quantify responses to leaf temperature (TI) and D were developed, the best of which was

gs = [1-k1(1-[Tl/Topt)]/k2√D,

where Topt is the leaf temperature at which maximal stomatal opening is observed and k1 and k2 are constants fitted by non-linear least squares regression analysis.

Calculation of the gain ratio of CO2 assimilation (A) to transpiration (E) (δA/δE) was complicated by effects of D on the relationship between A and leaf intercellular mol fraction of CO2 (CI). Calculation of δA/δE using A/CIrelationships derived by varying external CO2 mol fraction at constant D showed the gain ratio to be virtually constant (1.5 mmol mol-1) across a range of leaf temperatures and vapour mol fraction differences but, when calculated directly from the relationship between A and gs, a decrease in δA/δE with D was observed. Macadamia leaves have heavily sclerified bundle sheath extensions and it is considered that this dependence was an artefact due to non-uniform stomatal closure in response to increasing D. It is shown that, at any given temperature, a stomatal response of the form gsD-1/2 gives rise to an approximately constant δA/δE.

Leaf water and stomatal movement, visual observation of stomata in situ

 

 

Leaf water and stomatal movement in Gossypium and a method of direct visual observation of stomata in situ

by Lloyd F. E. (1913)

Francis E. Lloyd

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in Bull. Torrey Bot. Club 40: 1-2 –

https://archive.org/stream/jstor-2479849/2479849_djvu.txt

Francis E. Lloyd 

In a previous paper* it is shown that the rates of transpiration 
in cut shoots of the ocotillo, Fouquieria splendens, recorded by 
simultaneous volumetric readings and weighings, are not paraliel, 
but that the loss of water from the plant during the day is in 
excess of that taken up by the cut end of the shoot from the 
porometer. This result is in general harmony with the findings 
of Eberdtf with rooted plants of Helianthus annuus. It was not, 
however, found to be true in my study of the ocotillo that the loss 
of water takes place at a constant ratio during the hours of day- 
light, since the whole relation between the income and outgo may 
be reversed within a short space of time even during daylight by 
an apparently slight modification of the environmental condi- 
tions. This ready susceptibility of the plant lent color to the 
idea that the differences indicated by volumetric and gravimetric 
readings are measures of differences in the leaf moisture content, 
to be more briefly referred to as leaf water in the present paper.

RAP2.6L overexpression delays waterlogging induced premature senescence by increasing stomatal closure

 

 

RAP2.6L overexpression delays waterlogging induced premature senescence by increasing stomatal closure more than antioxidant enzyme activity

by Liu P., Sun F., Gao R., Dong H. (2012)

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in Plant Mol. Biol. 79: 609–622 – doi: 10.1007/s11103-012-9936-8 –

https://www.ncbi.nlm.nih.gov/pubmed/22661072

Abstract

Waterlogging usually results from overuse or poor management of irrigation water and is a serious constraint due to its damaging effects. RAP2.6L (At5g13330) overexpression enhances plant resistance to jasmonic acid, salicylic acid, abscisic acid (ABA) and ethylene in Arabidopsis thaliana. However, it is not known whether RAP2.6L overexpression in vivo improves plant tolerance to waterlogging stress.

In this study, the RAP2.6L transcript was induced by waterlogging or an ABA treatment, which was reduced after pretreatment with an ABA biosynthesis inhibitor tungstate. Water loss and membrane leakage were reduced in RAP2.6L overexpression plants under waterlogging stress. Time course analyses of ABA content and production of hydrogen peroxide (H(2)O(2)) showed that increased ABA precedes the increase of H(2)O(2).

It is also followed by a marked increase in the antioxidant enzyme activities. Increased ABA promoted stomatal closure and made leaves exhibit a delayed waterlogging induced premature senescence.

Furthermore, RAP2.6L overexpression caused significant increases in the transcripts of antioxidant enzyme genes APX1 (ascorbate peroxidase 1) and FSD1 (Fe-superoxide dismutase 1), the ABA biosynthesis gene ABA1 (ABA deficient 1) and signaling gene ABH1 (ABA-hypersensitive 1) and the waterlogging responsive gene ADH1 (alcohol dehydrogenase 1), while the transcript of ABI1 (ABA insensitive 1) was decreased.

ABA inhibits seed germination and seedling growth and phenotype analysis showed that the integration of abi1-1 mutation into the RAP2.6L overexpression lines reduces ABA sensitivity.

These suggest that RAP2.6L overexpression delays waterlogging induced premature senescence and might function through ABI1-mediated ABA signaling pathway.

H2S may represent a novel component downstream of NO in the ethylene-induced stomatal movement

 

 

Hydrogen sulfide may function downstream of nitric oxide in ethylene-induced stomatal closure in Vicia faba L

by Liu J., Hou Z., Liu G., Hou L., Liu X. (2012)

Jing LIU, Zhi-hui HOU, Guo-hua LIU, Li-xia HOU, Xin LIU, 

Key Laboratory of Plant Biotechnology in Universities of Shandong Province/College of Life Science, Qingdao Agricultural University, Qingdao 266109, P.R. China

===

in J. Integr. Agric. 11, 1644–1653. – doi: 10.1016/S2095-3119(12)60167-1 –

https://www.sciencedirect.com/science/article/pii/S2095311912601671

Abstract

Pharmacological, laser scanning confocal microscopic (LSCM), and spectrophotographic approaches were used to study the roles of hydrogen sulfide (H2S) and nitric oxide (NO) in signaling transduction of stomatal movement in response to ethylene in Vicia faba L.

Ethylene treatment resulted in the dose-dependent stomatal closure under light, and this effect was blocked by the inhibitors of H2S biosynthesis in V. faba L. Additionally, ethylene induces H2S generation and increases L-/D-cysteine desulfhydrase (pyridoxalphosphate-dependent enzyme) activity in leaves of V. faba L.

Inhibitors of H2S biosynthesis have no effect on the ethylene-induced stomatal closure, NO accumulation, and nitrate reductase (NR) activity in guard cells or leaves of V. faba L. Moreover, the ethylene-induced increase of H2S levels and L-/D-cysteine desulfhydrase activity declined when NO generation was inhibited.

Therefore, we conclude that H2S and NO probably are involved in the signal transduction pathway of ethylene-induced stomatal closure. H2S may represent a novel component downstream of NO in the ethylene-induced stomatal movement in V. faba L.

H2S and NO are involved in the signal transduction pathway of ethylene-induced stomatal closure

Figure 7 Effects of H2S synthesis inhibitors on ethephon-induced NO production in guard cells (a) or in leaves of Arabidopsis thaliana (b). Treatments: A, CK; B, 0.4 mmol/L AOA; C, 0.4 mmol/L NH2OH; D, 0.2 mmol/L C3H3KO3 + 0.2 mmol/L NH3.

 

Hydrogen sulfide induced by nitric oxide mediates ethylene-induced stomatal closure of Arabidopsis thaliana

by Liu J., Hou L., Liu G., Liu X., Wang X. (2011)

LIU Jing1 , HOU LiXia1 , LIU GuoHua1 , LIU Xin1* & WANG XueChen2

1 Key Laboratory of Plant Biotechnology in Universities of Shandong, Life Sciences College, Qingdao Agricultural University, Qingdao 266109, China;

2 State Key Laboratory of Plant Physiology and Biochemistry, College of Biological Sciences, China Agricultural University, Beijing 100094, China

===

in Chin. Sci. Bull. 56: 3547–3553 – doi: 10.1007/s11434-011-4819-y –

https://link.springer.com/content/pdf/10.1007/s11434-011-4819-y.pdf

Screen Shot 2018-05-23 at 10.27.45
Figure 9 Effects of 0.004% ethephon on NO levels in guard cells of wild-type Arabidopsis thaliana, and Atl-cdes and Atd-cdes mutants.

Abstract

Pharmacological, laser scanning confocal microscopic (LSCM), real-time PCR and spectrophotographic approaches are used to study the roles of hydrogen sulfide (H2S) and nitric oxide (NO) in signaling transduction of stomatal movement response to ethylene in Arabidopsis thaliana.

In the present study, inhibitors of H2S synthesis were found to block ethylene-induced stomatal closure of Arabidopsis. Treatment with ethylene induced H2S generation and increased L-/D-cysteine desulfhydrase (pyridoxalphosphate-dependent enzyme) activity in leaves. Quantitative PCR analysis showed AtL-CDes and AtD-CDes transcripts were induced by ethylene. It is suggested that ethylene-induced H2S levels and L-/D-cysteine desulfhydrase activity decreased when NO was compromised.

The data clearly show that ethylene was able to induce H2S generation and stomatal closure in Atnoa1 plants, but failed in the Atnia1,nia2 mutant. Inhibitors of H2S synthesis had no effect on ethylene-induced NO accumulation and nitrate reductase (NR) activity in guard cells or leaves of Arabidopsis, whereas ethylene was able to induce NO synthesis.

Therefore, we conclude that H2S and NO are involved in the signal transduction pathway of ethylene-induced stomatal closure. In Arabidopsis, H2S may represent a novel downstream indicator of NO during ethylene-induced stomatal movement.

The relationships between veins, stomata and epidermal cells in leaves, sepals and petals

 

 

Similar geometric rules govern the distribution of veins and stomata in petals, sepals and leaves

by Zhang F.-P., Carins-Murphy M. R., Cardoso A. A., Jordan G. J., Brodribb T. J. (2018)

Feng‐Ping Zhang, Madeline R. Carins Murphy, Amanda A. Cardoso, Gregory J. Jordan, Timothy J. Brodribb,
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in New Phytologist – https://doi.org/10.1111/nph.15210 –

https://nph.onlinelibrary.wiley.com/doi/abs/10.1111/nph.15210?af=R

Summary

  • Investment in leaf veins (supplying xylem water) is balanced by stomatal abundance, such that sufficient water transport is provided for stomata to remain open when soil water is abundant. This coordination is mediated by a common dependence of vein and stomatal densities on cell size. Flowers may not conform to this same developmental pattern if they depend on water supplied by the phloem or have high rates of nonstomatal transpiration.
  • We examined the relationships between veins, stomata and epidermal cells in leaves, sepals and petals of 27 angiosperms to determine whether common spacing rules applied to all tissues.
  • Regression analysis found no evidence for different relationships within organ types. Both vein and stomatal densities were strongly associated with epidermal cell size within organs, but, for a given epidermal cell size, petals had fewer veins and stomata than sepals, which had fewer than leaves.
  • Although our data support the concept of common scaling between veins and stomata in leaves and flowers, the large diversity in petal vein density suggests that, in some species, petal veins may be engaged in additional functions, such as the supply of water for high cuticular transpiration or for phloem delivery of water or carbohydrates.