Month: August 2015

Nitric oxide-induced stomatal closure in Arabidopsis thaliana

 

Lipoxygenase 2 functions in exogenous nitric oxide-induced stomatal closure in Arabidopsis thaliana

by Sun Y., Lv D., Wang W., Xu W., Wang L., Miao C., Lin H. H. (2015)

in Functional Plant Biology – http://dx.doi.org/10.1071/FP15151

Abstract

Nitric oxide (NO) and lipoxygenase (LOX)-derived oxylipins play important roles in stomatal closure in plants, and LOX–NO crosstalk has been indicated in mesophyll cells. However, whether the crosstalk also exists in guard cells is not clear and the detailed mechanisms remain unknown.

Here, we report that exogenous sodium nitroprusside (SNP, a NO donor)-induced stomatal closure was clearly impaired in the AtLOX2 null mutant lox2–1 compared with wild-type (WT)Arabidopsis thaliana (L.) Heynh. Patch clamp analysis showed that the SNP-suppressed activity of inward-rectifying potassium channels in lox2–1 guard cell protoplasts was reduced. Moreover, SNP promoted an increase in cytosolic Ca2+ concentration in guard cells of lox2–1 mutants was inhibited compared with the WT.

These results suggest that AtLOX2 plays an important role in NO-induced stomatal closure by affecting the cytosolic Ca2+ concentration increase and the activity of inward-rectifying potassium channels in guard cells. Furthermore, lox2–1 mutants showed a higher rate of leaf water loss and a relatively wider stomatal aperture than the WT under normal growth conditions.

These data imply that AtLOX2 might modulate stomatal movement by increasing oxylipin generation in A. thaliana.

See the text: CSIRO

Stomatal density in Quercus ilex seedlings grown in an ozone-enriched environment

 

Early and late adjustments of the photosynthetic traits and stomatal density in Quercus ilex L. grown in an ozone-enriched environment

by Fusaro L., Gerosa G., Salvatori E., Marzuoli R., Monga R., Kuzminsky E., Angelaccio C., Quarato D., Fares S. (2015)

in Plant Biology – Accepted Article (Accepted, unedited article published online and citable)

Abstract

Quercus ilex L. seedlings were exposed for one growing season in Open-Top Chambers to three levels of ozone (O3): charcoal filtered air, non-filtered air supplemented with +30% and +74% of ambient air O3.

Key functional parameters related to the photosynthetic performance and stomatal density were measured to evaluate the response mechanisms of Q. ilex to chronic O3 exposure, clarifying how ecophysiological traits are modulated during the season in an ozone-enriched environment.

Dark respiration showed an early response to ozone exposure, increasing approximately 45 % relative to charcoal filtered air in both O3 enriched treatments. At the end of the growing season, instead, maximum rate of assimilation (Amax) and stomatal conductance (gs) showed a decline (-13 and -36 %, for Amax and gs, respectively), only in plants under higher levels of O3. Photosystem I functionality supported the capacity of Q. ilex to cope with oxidative stress by adjusting the energy flow partitioning inside the photosystems. The response to O3 was also characterized by an increase of stomatal density in both enriched treatments relative to control.

Our results suggest that in order to improve the reliability of metrics for ozone-risk assessment, the seasonal changes of the response of gs and photosynthetic machinery to O3 stress should be considered.

See the text: Wiley Online Library

 

The understanding of CO2 signaling pathway in guard cells.

 

Guard cell hydrogen peroxide and nitric oxide mediate elevated CO2-induced stomatal movement in tomato

by Shi K., Li X., Zhang H., Zhang G., Liu Y., Zhou Y., Xia X., Chen Z., Yu J. (2015)

in New Phytologist – Early View (Online Version of Record published before inclusion in an issue)

Summary

  • Climate change as a consequence of increasing atmospheric CO2 influences plant photosynthesis and transpiration. Although the involvement of stomata in plant responses to elevated CO2 has been well established, the underlying mechanism of elevated CO2-induced stomatal movement remains largely unknown.
  • We used diverse techniques, including laser scanning confocal microscopy, transmission electron microscopy, biochemical methodologies and gene silencing to investigate the signaling pathway for elevated CO2-induced stomatal movement in tomato (Solanum lycopersicum).
  • Elevated CO2-induced stomatal closure was dependent on the production of RESPIRATORY BURST OXIDASE 1 (RBOH1)-mediated hydrogen peroxide (H2O2) and NITRATE REDUCTASE (NR)-mediated nitric oxide (NO) in guard cells in an abscisic acid (ABA)-independent manner. Silencing of OPEN STOMATA 1 (OST1) compromised the elevated CO2-induced accumulation of H2O2 and NO, upregulation of SLOW ANION CHANNEL ASSOCIATED 1 (SLAC1) gene expression and reduction of stomatal aperture, whereas silencing of RBOH1 or NR had no effects on the expression of OST1.
  • Our results demonstrate that as critical signaling molecules, RBOH1-dependent H2O2 and NR-dependent NO act downstream of OST1 that regulate SLAC1expression and elevated CO2-induced stomatal movement. This information is crucial to deepen the understanding of CO2 signaling pathway in guard cells.

See the text: Wiley Online Library

Stomatal Features in Some Shade Trees

Cooling Effects and Humidification Potentials in Relation to Stomatal Features in Some Shade Plants

by AbdulRamahan A. A., Olayinka B. U., Haruna M., Yussuf B. T., Aderemi M. O., Kolawole O. S., Omolokun K. T., Aluko T. A., Oladele F. A. (2013)

in International Journal of Applied Science and Technology Vol. 3 No. 8; December 2013

Abstract

Thirty shade trees namely Lonchocarpus cyanenscens, Albizia lebbeck, Blidelia ferruginea, Prosobis africana, Burkea africana, Lophira lanceolata, Ficus elastica, Ficus trichopoda, Annona senegalensis, Citrus aurantifolia, Gliricidia sepium, Dioclea reflexa, Gmelina arborea, Acacia auriculiformis, Anacardium occidentale, Vitellaria paradoxa, Parkia biglobosa, Citrus paradisi, Citrus reticulata, Citrus limon, Citrus sinensis, Terminalia catappa, Tectonia grandis, Delonix regia, Mangifera indica, Thevetia neriifolia, Plumeria alba, Blighia sapida, Azadirachta indica, and Daniela olivieri were studied to determine their canopy characteristics in relationship to stomatal features possessed and the rate at which they transpire.

The canopy characteristics vary in all species with D. oliveri, T. catappa and L. cyanenscens, etc has the widest canopy while P. alba and C. limon has the narrowest canopy. Density of leaves (LD) is highest in T. neriifolia and D. regia, and it is lowest in P. alba, B. sapida, T. grandis, T. nerifolia. The tree height is tallest in L. cyanenscens followed by A. auriculiformis , G. arborea and D. oliveri .

In each species, leaves were taken and observed anatomically to reveal stomatal features and rate of transpiration; for instance T. catappa, A. auriculiformis and others that possessed amphistomatic leaves with heterogeneous stomatal complex types (SCTS) transpired faster than species such as T. grandis, A. senegalensis, A. occidentale etc with hypostomatic leaves and homogeneous SCTS.

Stomata in the studied species were all more than 15µm with A. auriculiformis having larger size (73.75µm) while D. regia possessed the smaller size (47µm). T. catappa has the highest stomatal density of 91.00mm2 while D. regia has the lowest stomatal density of 8.25mm2 .

Coolness provided by the shade trees is evidence in the temperature under the trees and in the open space; temperature is higher in the open than under the trees in all the 30 species studied. Based on the canopy characteristics and stomatal features possessed by each of these shade plants as well as their rate of transpiration, species such as T. catappa, A. indica, A. lebbeck, F. trichopoda, L. cyanenscens, D. regia, D. oliveri, and A. auriculiformis are the most preferable shade plant.

Read the full article: IJAST

Stomata in Umbelliferae (Apiaceae)

 

Stomatal types in the Umbelliferae and their taxonomic value Tribe Apiaea, subtribe Foeniculinae

by Ostroumova T. A., Lavrova T. V. (1991)

===

in Feddes Repertorium 102, (5-6), 385–394, 1991

Abstract

Stomatal types of 65 species representing 32 genera of the subtribe Foeniculinae have been investigated, the material origined from the territory of the USSR and some other regions of Asia and Europe.

Anomocytic, hemiparacytic, diacytic, paracytic and anisocytic types have been registered. Predominant types in many genera were anomocytic or anomocytic along with hemiparacytic, rarely a mixture of hemiparacytic and anisocytic; some genera had significant number (sometimes predominance) of diacytic and paracytic types. The genera Kadenia and Macrosciadium were found to be extremely variable as concerns stomatal types.

 

See the text: Wiley Online Library

Stomata and water balance

Photo credit: Google

The control of stomata by water balance

by Buckley T. N. (2005)

in New Phytol. 168(2): 275-292 – doi: 10.1111/j.1469-8137.2005.01543.x

CrossRef Medline Web of Science Google Scholar – Abstract – Full Article (HTML) – PDF(570K) – References – Web of Science® Times Cited: 96

Summary

It is clear that stomata play a critical role in regulating water loss from terrestrial vegetation. What is not clear is how this regulation is achieved. Stomata appear to respond to perturbations of many aspects of the soil–plant–atmosphere hydraulic continuum, but there is little agreement regarding the mechanism (or mechanisms) by which stomata sense such perturbations.

This review discusses feedback and feedforward mechanisms by which hydraulic perturbations are putatively transduced into stomatal movements, in relation to generic empirical features of those responses.

It is argued that a metabolically mediated feedback response of stomatal guard cells to the water status in their immediate vicinity (‘hydro-active local feedback’) remains the best explanation for many well-known features of hydraulically related stomatal behaviour, such as transient ‘wrong-way’ responses and the equivalence of hydraulic supply and demand as stomatal effectors.

Furthermore, many curious phenomena that appear inconsistent with feedback, such as ‘apparent feedforward’ humidity responses and ‘isohydric’ behaviour (water potential homeostasis), are in fact expected to emerge from the juxtaposition of hydro-active local feedback and the well-known hysteretic and threshold-like effect of water potential on xylem hydraulic resistance.

Read the full article: Wiley Online Library

Stomatal trait diversity amongst grasses

 

Photosynthetic pathway and ecological adaptation explain stomatal trait diversity amongst grasses.

by Taylor S. H., Franks P. J., Hulme S. P., Spriggs E., Christin P. A, Edwards J. E., Woodward F. I., Osborne C. P. (2012)

in New Phytologist 193:387–396. –

doi: 10.1111/j.1469-8137.2011.03935.x –

PubMed/NCB – Google Scholar

Summary

  • •
    The evolution of C4 photosynthesis in plants has allowed the maintenance of high CO2 assimilation rates despite lower stomatal conductances. This underpins the greater water-use efficiency in C4 species and their tendency to occupy drier, more seasonal environments than their C3 relatives.
  • •
    The basis of interspecific variation in maximum stomatal conductance to water (gmax), as defined by stomatal density and size, was investigated in a common-environment screening experiment. Stomatal traits were measured in 28 species from seven grass lineages, and comparative methods were used to test for predicted effects of C3 and C4 photosynthesis, annual precipitation and habitat wetness on gmax.
  • •
    Novel results were as follows: significant phylogenetic patterns exist in gmax and its determinants, stomatal size and stomatal density; C4 species consistently have lower gmax than their C3 relatives, associated with a shift towards smaller stomata at a given density. A direct relationship between gmax and precipitation was not supported. However, we confirmed associations between C4 photosynthesis and lower precipitation, and showed steeper stomatal size–density relationships and higher gmax in wetter habitats.
  • •
    The observed relationships between stomatal patterning, photosynthetic pathway and habitat provide a clear example of the interplay between anatomical traits, physiological innovation and ecological adaptation in plants.

See the full article: Wiley Online Library

The relationship between stomatal characteristics and elevation

Photo credit: PLOS

Elevation-Related Variation in Leaf Stomatal Traits as a Function of Plant Functional Type: Evidence from Changbai Mountain, China

by Wang R., Yu G., He N., Wang Q., Xia F., Zhao N., Xu Z., Ge J. (2014)

in PLoS ONE 9(12): e115395. – doi:10.1371/journal.pone.0115395

Abstract

Understanding the variation in stomatal characteristics in relation to climatic gradients can reveal the adaptation strategies of plants, and help us to predict their responses to future climate changes.

In this study, we investigated stomatal density (SD) and stomatal length (SL) in 150 plant species along an elevation gradient (540–2357 m) in Changbai Mountain, China, and explored the patterns and drivers of stomatal characteristics across species and plant functional types (PFTs: trees, shrubs, and herbs).

The average values of SD and SL for all species combined were 156 mm–2 and 35 µm, respectively. SD was higher in trees (224 mm–2) than in shrubs (156 mm–2) or herbs (124 mm–2), and SL was largest in herbs (37 µm). SD was negatively correlated with SL in all species and PFTs (P<0.01). The relationship between stomatal characteristics and elevation differed among PFTs. In trees, SD decreased and SL increased with elevation; in shrubs and herbs, SD initially increased and then decreased. Elevation-related differences in SL were not significant. PFT explained 7.20–17.6% of the total variation in SD and SL; the contributions of CO2 partial pressure (), precipitation, and soil water content (SWC) were weak (0.02–2.28%).

Our findings suggest that elevation-related patterns of stomatal characteristics in leaves are primarily a function of PFT, and highlight the importance of differences among PFTs in modeling gas exchange in terrestrial ecosystems under global climate change.

Scanning electron microscopy of stomata

 

The application of scanning electron microscopy in plant anatomy

by Merkulov L., Krstić L., Luković J., Bokorov M. (—-)

===

Serbian Society for Microscopy

Introduction

For investigations of the structure of vegetative and reproductive plant organs, scanning electron microscopy (SEM) is of great importance in study of dermal tissue anatomy and its special structures (stomata, glandular and non-glandular trichomes, papillae, specialized epidermal cells, pollen grain exinas, ornamentation of seed coats and outer layers of pericarps).

Dermal tissue as an outer leyer tissue towards the environment, is specialized structure with several functional demands: effective protection, transport of gasses, transpiration as well as secretion of different metabolic products through specialized cells. As this tissue is in direct contact with the environment, it clearly expresses adaptive structural characteristics induced by numerous exogenous factors (stomata number and size, stomata distribution, amount of epicuticular wax, etc.).

On the other hand, some dermal tissue characteristics are determined by genetic inheritance and therefore could not be changed, or change very little, under the influence of environmental factors (types of stomata, trichomes, cuticle, epicuticular wax shape, presence of specialized epidermal cells, etc.) and represent taxonomically important diagnostic characters. SEM is of a great significance in determination and analysis of those characters.

Read the full text: VIN

B1-Type Cyclin-Dependent Kinases and stomata in Arabidopsis

B1-Type Cyclin-Dependent Kinases Are Essential for the Formation of Stomatal Complexes in Arabidopsis thaliana

by Boudolf V., Barrôco R., de Almeida Engler J., Verkest A., Beeckman T., Naudts M., Inzé D., De Veylder L. (2004)

in The Plant Cell April 2004, vol. 16, no. 4, 945-955. – doi: http:/​/​dx.​doi.​org/​10.​1105/​tpc.​021774 – 

http://www.plantcell.org/content/16/4/945.abstract

F2.medium
Figure 2. In Situ Localization of CDKA;1 and CDKB1;1 mRNA. (A) to (C) Longitudinal section through cotyledons harvested 5 d after germination. White dots in dark-field images show the hybridization signal. Inset, bright-field image of the same section, with black dots showing the hybridization signal. (A) CDKA;1 expression. (B) CDKB1;1 expression. (C) Expression of neomycin phosphotransferase II gene (control probe). (D) and (F) CDKA;1 expression in a transverse and a paradermal section through a stoma, respectively. (E) and (G) CDKB1;1 expression in a transverse and a paradermal section through a stoma, respectively. Red arrowheads indicate the GCs. Scale bars in (A) to (C) = 50 μm; bars in (D) to (G) = 10 μm. – http://www.plantcell.org/content/16/4/945/F2.medium.gif

Abstract

Cyclin-dependent kinases (CDKs) are key regulators of the cell cycle. In yeasts, only one CDK is sufficient to drive cells through the cell cycle, whereas higher eukaryotes developed a family of related CDKs. Curiously, plants contain a unique class of CDKs (B-type CDKs), whose function is still unclear. We show that the CDKB1;1 gene of Arabidopsis (Arabidopsis thaliana) is highly expressed in guard cells and stomatal precursor cells of cotyledons, suggesting a prominent role for B-type CDKs in stomatal development. In accordance, transgenic Arabidopsis plants with reduced B-type CDK activity had a decreased stomatal index because of an early block of meristemoid division and inhibition of satellite meristemoid formation. Many aberrant stomatal cells were observed, all of them blocked in the G2 phase of the cell cycle. Although division of stomatal precursors was inhibited, cells still acquired stomatal identity, illustrating that stomatal cell differentiation is independent of cellular and nuclear division.

Read the full article: The Plant Cell