Stomata in some Convolvulaceae

 

Photo credit: Google

Merremia emarginata – Kupit-kupit

(Evolvulus_alsinoides)_Dwarf_Morning-glory_at_Bhongir_01
Photo credit Google – Evolvulus alsinoides – https://upload.wikimedia.org/wikipedia/commons/7/72/(Evolvulus_alsinoides)_Dwarf_Morning-glory_at_Bhongir_01.jpg

 

Epidermal structures and development of stomata in some Convolvulaceae

by Pant D. D., Banerji R. (1965)

Divya Darshan Pant, Rina Banerji

Allahabad University, India

in Senckenbergiana Biologica 46: 155-173

 

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Cuscuta reflexa habit3
Photo credit Google – Cuscuta reflexa – http://www.eflorakkl.in/FloraImages/Cuscuta%20reflexa%20habit3.jpg

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A model of stomatal conductance for C4 photosynthesis

 

 

A dynamic hydro-mechanical and biochemical model of stomatal conductance for C4 photosynthesis

by Bellasio C., Quirk J., Buckley T. N., Beerling D. J. (2017)

1. Australian National University CITY: Acton STATE: ACT POSTAL_CODE: 2601 Australia [AU]

2. The University Of Sheffield CITY: Sheffield United Kingdom [GB].

3. The University of Sydney CITY: Narrabri STATE: NSW POSTAL_CODE: 2390 Australia [AU].

4. University of Sheffield CITY: Sheffield United Kingdom [GB].

Thomas_Buckley2
Thomas N Buckley, University of Sydney

https://www.researchgate.net/publication/318721627_A_dynamic_hydro-mechanical_and_biochemical_model_of_stomatal_conductance_for_C4_photosynthesis?discoverMore=1

Abstract
C4 plants are major grain (maize, sorghum), sugar (sugarcane) and biofuel (Miscanthus) producers, and contribute ~20% to global productivity.
Plants lose water through stomatal pores in order to acquire CO2 (assimilation, A), and control their carbon-for-water balance by regulating stomatal conductance (gS). The ability to mechanistically predict gS and A in response to atmospheric CO2, water availability and time is critical for simulating stomatal control of plant-atmospheric carbon and water exchange under current, past or future environmental conditions.
Yet, dynamic mechanistic models for gS are lacking, especially for C4 photosynthesis. We developed and coupled a hydro-mechanical model of stomatal behaviour with a biochemical model of C4 photosynthesis, calibrated using gas exchange measurements in maize, and extended the coupled model with time- explicit functions to predict dynamic responses.
We demonstrated the wider applicability of the model with three additional C4 grass species in which interspecific differences in stomatal behaviour could be accounted for by fitting a single parameter.
The model accurately predicted steady-state responses of gS to light, atmospheric CO2 and O2, soil drying and evaporative demand, as well as dynamic responses to light intensity.
Further analyses suggest the effect of variable leaf hydraulic conductance is negligible.
Based on the model, we derived a set of equations suitable for incorporation in land surface models. Our model illuminates the processes underpinning stomatal control in C4 plants and suggests the hydraulic benefits associated with fast stomatal responses of C4 grasses may have supported the evolution of C4 photosynthesis.

Stomatal characteristics at different ploidy levels

Photo credit: Google

Coffea canephora. Robust Coffee

Personal communication by Manoj Kumar Mishra with submission form

Stomatal characteristics at different ploidy levels in Coffea L.

by Mishra M. K. (1997)

Manoj Kumar Mishra

in Annals of Botany 80(5): 689–692 – https://doi.org/10.1006/anbo.1997.0491 –

https://academic.oup.com/aob/article-lookup/doi/10.1006/anbo.1997.0491

Abstract

Stomatal frequency, epidermal cell frequency, stomatal guard cell length and stomatal index were examined at different ploidy levels in Coffea.

In general, stomatal and epidermal cell frequency per unit leaf area decreased while stomatal guard cell length increased with an increase in ploidy. The reduction in stomatal frequency at higher ploidy levels was mainly a result of larger epidermal cells.

In the case of C. canephora (cultivar S.274) a significant reduction in stomatal frequency was noticed from diploid to tetraploid level which was due to both larger epidermal cell size and less stomatal differentiation at the tetraploid level.

Besides the effect of ploidy on stomatal frequency and guard cell length, genotypic differences in stomatal frequency and stomatal guard cell length were also observed among cultivars of the same ploidy level.

Although variation in stomatal frequency among cultivars was found to be associated with the difference in stomatal to epidermal cell ratio, variation in guard cell length was attributed to differential genetic architecture.

In the present study a highly significant positive correlation ( r =0.82) between stomatal and epidermal cell frequency and high negative correlations between stomatal frequency and guard cell lengthr =-0.91) and epidermal cell frequency and stomatal guard cell length ( r =-0.93) were obtained.

The study also indicated that stomatal frequency can be predicted with 83 and 87% accuracy, respectively, by measuring stomatal guard cell length in coffee.

Stomatal responses to water stress in an ABA-unresponsive hybrid poplar

Photo credit: Google

Western Balsam Poplar – Populus trichocarpa 

 

form1
Photo credit Google -Populus balsamifera ssp. trichocarpa is native to North America.  – http://dendro.cnre.vt.edu/dendrology/images/Populus%20balsamifera%20ssp.%20trichocarpa/form1.jpg

 

Responses to water stress in an ABA – unresponsive hybrid poplar (Populus koreana x trichocarpa cv. Peace) I. Stomatal function

by Ridolfi M., Fauveau M. L., Label P., Garrec J. P., Dreyer E. (1996)

in New Phytologist, 1996, 134 ( 3): 445-454 – DOI: 10.1111/j.1469-8137.1996.tb04361.x – 

http://onlinelibrary.wiley.com/doi/10.1111/j.1469-8137.1996.tb04361.x/full

SUMMARY

The poplar cultivar ‘Peace’ (Populus trichocarpa×koreana) displays abnormal stomatal behaviour with a lack of sensitivity to exogenous abscisic acid (ABA) in mature leaves.

We report details of the leaf-age dependency of this feature, and present the responses of stomata to diverse closing stimuli in addition to ABA.

Soil water depletion induced complete stomatal closure of the youngest leaves, whereas the oldest exhibited almost no closure. By contrast, no such age effect was observed in stomatal sensitivity to ABA: a complete lack of closure was observed on all leaves, even with 10-3 M ABA.

Moreover, a preconditioning by drought did not restore the ability of stomata to close in response to ABA. Supplying detached leaves with Ca2+ (5 × 10-2 M) was effective in inducing stomatal closure in the youngest leaves, and reproduced the age-dependent drought response.

These results support the hypothesis that drought control of stomatal conductance in ‘Peace’ is ABA-independent, and could involve calcium ions. A loss of stomatal sensitivity to calcium, with leaf maturation, could explain the dependency of stomatal closure on leafage.

Xylem sap concentrations of calcium were lower than those required to close stomata, and no drought-induced increase was recorded. The mature leaves were also insensitive to increased ambient CO2, but darkness promoted partial stomatal closure.

Stomatal adjustment mechanisms should show patterned variation

 

 

Speculations on carbon dioxide starvation, late tertiary evolution of stomatal regulation and floristic modernization.

by Robinson J. M. (1994)

Umweltforschungszentrwn Leipzig-Halle, Permoserstr. 15, 04318 Leipzig, Germany

in Plant, Cell and Environment 1994;17345354 – DOI: 10.1111/j.1365-3040.1994.tb00303.x – 

Google Scholar – 

http://onlinelibrary.wiley.com/doi/10.1111/j.1365-3040.1994.tb00303.x/full

ABSTRACT

Ambient atmospheric CO2 concentration ([CO2]a) has apparently declined from values above 200μmol mol−1 to values below 200μmol mol−1 within the last several million years. The lower end of this range is marginal for C3 plants.

I hypothesize that:

(1) declining [CO2]a imposed a physiological strain on plants, and plant taxa evolving under declining [CO2]a tended to develop compensating mechanisms, including increased stomatal efficiency;

(2) angiosperms were better able to adjust to declining [CO2]than were gymnosperms and pteridophytes; and

(3) angiosperm adjustment has been uneven.

Fast-evolving taxa (e.g. grasses and herbs) have been better able to adapt to CO2 starvation. If these propositions are true, stomatal adjustment mechanisms should show patterned variation, and a single pattern of stomatal regulation cannot be assumed.

 

ABA, temperature and stomata

 

Photo credit: Google

Zea mays 

The effects of temperature and ABA on stomata of Zea mays L.

by Rodriguez J. L., Davies W. J. (1982)

in J. Exp. Bot. 33, 977–987. – doi: 10.1093/jxb/33.5.977 –

CrossRef Full Text | Google Scholar

https://academic.oup.com/jxb/article-abstract/33/5/977/566674/The-Effects-of-Temperature-and-ABA-on-Stomata-of?redirectedFrom=fulltext

 

Abstract

Epidermal fragments were removed from maize leaves by tearing parallel to the veins. These were incubated at a number of different temperatures in several concentrations of ABA.

The sensitivity of stomata to temperature was dependent upon the technique used to incubate epidermis. Generally, the widest apertures were recorded at around 25°C.

In all experiments, stomata incubated at low (10°C) temperatures on 5.6 × 10−4 M ABA showed wider apertures than those incubated on distilled water. This ABA-stimulated stomatal opening was accompanied by an increase in the intensity of potassium staining in the guard cells. At 25 °C, epidermis incubated on several concentrations of ABA showed some stomatal closure, decreased potassium staining in the guard cells and increased potassium staining in the subsidiary cells.

Inhibition in stomata by ABA is mediated through protein phosphatases

 

 

Blue light-induced apoplastic acidification of Arabidopsis thaliana guard cells: inhibition by ABA is mediated through protein phosphatases.

by Roelfsema M. R. G., Staal M., Prins H. B. A. (1998)

M. Rob G. Roelfsema, Marten Staal, Hidde B. A. Prins

in  Physiologia Plantarum 103: 466474 –DOI: 10.1034/j.1399-3054.1998.1030404.x – 

Google Scholar – 

http://onlinelibrary.wiley.com/doi/10.1034/j.1399-3054.1998.1030404.x/full

Abstract

The phytohormone abscisic acid (ABA) inhibits blue light-induced apoplastic acidification of guard cells. The signal transduction pathway of ABA, mediating this response, was studied using ABA-insensitive (abi) mutants of Arabidopsis thaliana.

Apoplastic acidification was monitored with a flat tipped pH-electrode placed on epidermal strips, in which only guard cells were viable. Blue light-induced apoplastic acidification was reduced by vanadate and diethylstilbestrol (DES), indicating involvement of plasma membrane-bound H+-ATPases.

In wild type epidermal strips, ABA reduced blue light-induced acidification to 63%. The inhibition did not result from an increased cytoplasmic free Ca2+concentration in guard cells, since factors that increase the Ca2+ concentration stimulated apoplastic acidification.

Apoplastic acidification was not inhibited by ABA in abi1 and abi2 mutants. In abi1 epidermal strips ABA had no effect on the acidification rate, while it stimulated apoplastic acidification in abi2.

The ABA response in both mutants could be partially restored with protein kinase and phosphatase inhibitors. The abi1 guard cells became ABA responsive in the presence of okadaic acid, a protein phosphatase inhibitor. In abi2 guard cells the wild type ABA response was partially restored by K-252a, a protein kinase inhibitor.

Apoplastic inhibition is thus mediated through the protein phosphatases encoded by ABI1 and ABI2. The results with protein kinase and protein phosphatase inhibitors indicate that ABI1 and ABI2 are involved in separate signal transduction pathways.