Stomatal uptake of O3 in aspen and aspen-birch forests under free-air CO2 and O3 enrichment
by Uddling J., Hogg A. J., Teclaw R. M., Mary Anne Carroll M. A., Ellsworth D. S. (2010)
Johan Uddling a, *, Alan J. Hogg b, d, Ronald M. Teclaw c, Mary Anne Carroll d, e, f, David S. Ellsworth g
a Department of Plant and Environmental Sciences, University of Gothenburg, P.O. Box 461, SE-405 30 Göteborg, Sweden b Sweetland Writing Center, University of Michigan, 434 S. State St., Ann Arbor, MI 48109, USA c USDA Forest Service, Northern Research Station, Institute for Applied Ecosystem Studies, Rhinelander, WI 54501, USA d Department of Atmospheric, Oceanic, and Space Sciences, 2455 Hayward, University of Michigan, Ann Arbor, MI 48109, USA
e Department of Chemistry, University of Michigan, Ann Arbor, MI 48109, USA
f Department of Geological Sciences, University of Michigan, Ann Arbor, MI 48109, USA g Centre for Plant and Food Science, University of Western Sydney, Locked Bag 1797, Penrith South DC NSW 1797, Australia
Rising atmospheric carbon dioxide (CO2) may alleviate the toxicological impacts of concurrently rising tropospheric ozone (O3) during the present century if higher CO2 is accompanied by lower stomatal conductance (gs), as assumed by many models.
We investigated how elevated concentrations of CO2 and O3, alone and in combination, affected the accumulated stomatal flux of O3 (AFst) by canopies and sun leaves in closed aspen and aspen-birch forests in the free-air CO2–O3 enrichment experiment near Rhinelander, Wisconsin.
Stomatal conductance for O3 was derived from sap flux data and AFst was estimated either neglecting or accounting for the potential influence of non-stomatal leaf surface O3 deposition. Leaf-level AFst (AFstl) was not reduced by elevated CO2.
Instead, there was a significant CO2 O3 interaction on AFstl, as a consequence of lower values of gs in control plots and the combination treatment than in the two single-gas treatments.
In addition, aspen leaves had higher AFstl than birch leaves, and estimates of AFstl were not very sensitive to non-stomatal leaf surface O3 deposition.
Our results suggest that model projections of large CO2-induced reductions in gs alleviating the adverse effect of rising tropospheric O3 may not be reasonable for northern hardwood forests.
A three dimensional appreciation of the guard ce11 morphology coupled with ultrastructural studies should lead to a better understanding of their still obscure dynamics of movement. We have found the SEM of great value not only in studies of the surface details of stomata but also in resolving the structures and relationships that exist between the guard and subsidiary cells. We now report the isolation and SEM studies of guard cells from nine genera of plants.
Guard cells were isolated from the following plants: Psilotum nudum, four species of Equisetum, Cycas revoluta, Ceratozamia sp., Pinus sylvestris, Ephedra cochuma, Welwitschia mirabilis, Euphorbia tirucalli and Allium cepa.
To assess ozone risks to temperate deciduous forest trees in East Asia, the stomatal ozone uptake was estimated based on a flux-based modeling approach.
In this model, key parameters were obtained from scientific literatures on deciduous tree species in East Asia. In addition, regional characteristics of the leaf duration were estimated using a phenological model.
The results showed a difference in spatial pattern between AFst0 (accumulative stomatal ozone uptake) and AOT40 (accumulative exposure above a threshold concentration of 40 ppb during daylight hours). Although most of the areas of high ozone concentration corresponded to humid climate areas, not only the ozone concentration, but also the length of the leaf duration and the species-specific stomatal response to environmental factors, limited AFst0 in East Asia.
These results suggested that an approach based on stomatal ozone uptake would be a useful tool for ozone risk assessment in East Asia.
Taxonomic significance of leaf surface morphology in Aloe section Pictae (Xanthorrhoeaceae)
by Olwen M. G., Simmonds M. S. J., Smith G. F., Van Wijk A. E. (2009)
OLWEN M. GRACE1,2*, MONIQUE S. J. SIMMONDS FLS1, GIDEON F. SMITH2,3 and ABRAHAM E. VAN WYK FLS2
1 Royal Botanic Gardens, Kew, Surrey TW9 3AB, UK
2 Department of Plant Science, University of Pretoria, Pretoria 0002, South Africa
3 South African National Biodiversity Institute, Private Bag 101, Pretoria 0002, South Africa
in Botanical Journal of the Linnean Society 160: 418–428 –
Figure 1. Scanning electron micrograph of stomatal complex on adaxial leaf surface of Aloe umfoloziensis in transverse section: ec, epistomatal chamber; g, guard cell; i, inner cuticular ledge; l, lobe; o, outer cuticular ledge; s, subsidiary cell; sc, substomatal chamber. Scale bar, 10 mm.
Leaf surface morphology was analysed in 32 species representing the maculate species complex (the poorly resolved section Pictae) in the genus Aloe (Xanthorrhoeaceae).
Few comparative morphological data are available for the complex. Leaf surface and stomatal characters observed by scanning electron microscopy show taxonomically significant interspecific variation. Most species are characterized by irregularly outlined, four- to six-sided epidermal cells, the periclinal walls of which are flat and embellished with micropapillae and the anticlinal walls of which are indicated by channels on the leaf surface.
The outer stomatal pore is typically sunken or plane and surrounded by four lobes on the leaf surface that may overarch the epistomatal chamber. The guard cells have distinct outer and inner stomatal ledges.
Two geographical groups, comprising southern and east African species, are distinguishable by their leaf surface morphology. These characters are diagnostic in A. ellenbeckii, A. prinslooi and A. suffulta and support changes in the delimitation of A. greatheadii, A. macrocarpa and A. swynnertonii.
Figure 7. Analysis of functional relationship among heterotrimeric G protein, H2O2, and ExtCaM in guard cells. A, Effects of activator of G protein (400 ng/mL CTX) and inhibitor of NADPH oxidase (10 mM DPI) or scavenger of H2O2 (100 units/mL CAT) on V. faba stomatal closure. Control, Open stomata were kept in MES buffer for 2 h under light, then the stomatal aperture was treated as 100%; CTX, open stomata were treated with 1028 M CTX solution; CTX 1 DPI, open stomata were treated with 400 ng/mL CTX plus 10 mM DPI; CTX 1 CAT, open stomata were pretreated with 400 ng/mL CTX plus 100 units/mL CAT. Each assay was repeated three times. The data were presented as mean 6 SE (n 5 150). B, Fluorescent changes and (C) quantitative curve of H2O2 reflected with 50 mM H2DCF-DA after addition CaM in WT and gap1. Bar540mm.
Extracellular Calmodulin-Induced Stomatal Closure Is Mediated by Heterotrimeric G Protein and H2O2
by Chen Y.-L., Huang R., Xiao Y.-M., Lü P., Chen J., Wang X.-C. (2004)
Extracellular calmodulin (ExtCaM) exerts multiple functions in animals and plants, but the mode of ExtCaM action is not well understood.
In this paper, we provide evidence that ExtCaM stimulates a cascade of intracellular signaling events to regulate stomatal movement. Analysis of the changes of cytosolic free Ca21 ([Ca21]cyt) and H2O2 in Vicia faba guard cells combined with epidermal strip bioassay suggests that ExtCaM induces an increase in both H2O2 levels and [Ca21]cyt, leading to a reduction in stomatal aperture.
Pharmacological studies implicate heterotrimeric G protein in transmitting the ExtCaM signal, acting upstream of [Ca21]cyt elevation, and generating H2O2 in guard cell responses.
To further test the role of heterotrimeric G protein in ExtCaM signaling in stomatal closure, we checked guard cell responses in the Arabidopsis (Arabidopsis thaliana) Ga-subunit- null gpa1 mutants and cGa overexpression lines.
We found that gpa1 mutants were insensitive to ExtCaM stimulation of stomatal closure, whereas cGa overexpression enhanced the guard cell response to ExtCaM.
Furthermore, gpa1 mutants are impaired in ExtCaM induction of H2O2 generation in guard cells.
Taken together, our results strongly suggest that ExtCaM activates an intracellular signaling pathway involving activation of a heterotrimeric G protein, H2O2 generation, and changes in [Ca21]cyt in the regulation of stomatal movements.
The purpose of this research was to know comparative analysis of leaf stomata types in trees Swietenia macrophylla King and Polyalthia longifolia Bent & Hook. Var. Pendulain Makassar City.
This research has been conducted in A.P. Pettarani Street and Industrial Area Makassar. This research used modification method acetonethen performed a descriptive analysis.
The results showed that stomatal type of Swietenia macrophylla and Polyalthia longifolia is parasytic and phanerophor.
The highest density of leaf stomata on Swietenia macrophylla King is 877 stomata mm-2 in Industrial Area Makassar and the lowest density of stomata on the leaf Polyalthia longifolia Bent & Hook. var. Pendula is 411 stomata mm-2, in A.P. Pettarani Street.
Stomata adalah celah atau lubang yang berada padaorgan tumbuhan yang berwarna hijau yakni daun. Stotamadibatasi oleh sel khusus yang disebut sel penjaga atau sel penutup dan dikelilingi oleh sel tetangga. Peran penting stomata yaitu sebagai pertukaran gas O2 dan CO2 sebagai hasil dari fotosintesis dan respirasi aerob, penguapan atau transpirasi, serta mencegah kehilangan air. Praktikum ini bertujuan untukmengetahui pengaruh tekanan turgor terhadap membuka danmenutupnya stomata. Praktikum ini dilakukan pengamatan terhadap membukadan menutupnya stomata pada Rhoeo discolor. Pengamatandilakukan secara langsung menggunakan mikroskop terhadap sayatan daun Rhoeo discolor untuk mengamati stomatanya.Sayatan daun Rhoeo discolor diberi perlakuan terhadap air danlarutan gula, kemudian menghitung pengaruhnya terhadapmembuka atau menutupnya stomata dan menghitung jumlahnya. Hasil praktikum menunjukkan bahwa stomata yang diberi perlakuan dengan tetesan air lebih banyak yang terbukadaripada tertutup. Stomata yang diberi perlakuan larutan gulamenunjukkan banyak stomata yang tertutup daripada yangterbuka, karena konsentrasi larutan gula lebih tinggidibandingkan cairan intersel sehingga cairan didalam selhipotonis dan diluar sel menjadi hipertonis. Kemudian airmengakibatkan sel penjaga menjadi flacid dan menutup.