The stomata of grasses have a special feature: The pore is bordered by two pairs of cells where other plants only have a single cell pair. Guard cells of all six species had inner wall thickenings, while Arabidopsis and Commelina had extremely thick ones. Guard Cell vs Epidermal Cell The difference between guard cell and epidermal cell can be observed in the structure, content, and function of each cell type. Die Spaltöffnungen (mit phylogenetischen Ausblicken) 1, Evidence for in vitro binding of pectin side chains to cellulose. zðáâ½æ| 6¾7“iF-Æ­'7“1S0b(€ÄÎP%ã$i.°+øS¨ÑÐ-{½kd“QŽV*ä°×øìxjóø9Æ“Ú(ŽÉIeÛÌaӈ-|/ø¥õ¤ þjÙÇ'bL€Ó3e„ÌVG†7–¸Î¸ßîå”àŠ²1øIçÊ'॓œ+Ü UÓÅ+gn£PÖé The representative species, family, habitat and their stomatal attributes*. Grass is a mono-cot. All mono-cot plants have D-bell shaped stomata. Grass stomata open and close much faster than stomata from a variety of other species (Johnsson et al. The orientation colour pie-chart codes the cellulose microfibril orientation for every image. 618826) to S.H.-S. Brodribb TJ, McAdam SAM, Jordan GJ, Feild TS. The subsidiary cells alongside these dumbbell-resembling cells … As lignin is a natural fluorochrome, we carried out fluorescence confocal microscopy imaging of lignin. and S.H. *The number of stomata on a plant leaf/organ is highly dependent on the type of plant as wel… The stomatal density, guard cell lengths on the adaxial and abaxial leaf epidermis and the stomatal type in each family are described and the relationship between stomatal density and guard cell size is reviewed. In Z. mays and other grasses subsidiary cells are always in pairs flanking the guard cells, are uniquely shaped, are more pectin-rich … Published by Oxford University Press on behalf of the Annals of Botany Company. The guard cells control the size of the stomatal opening, and thus control the amount of gas exchange and transpiration. Fixed boundary conditions were assumed for the stoma edges and a uniform pressure was assumed within the stoma (Fig. Crystalline anisotropic materials are birefringent and can therefore be examined using polarized light microscopy. This results in opening of stomata. This work was supported by the Israel Science Foundation (I-CORE grant no. The 'veins' are a dense network of xylem, which supply water for photosynthesis, and phloem, which remove the sugars produced by photosynthesis.The pattern of the veins is called 'venation'. From these studies it was established that during the early stage of guard cell differentiation in grasses, Our results demonstrate several additional differences in stomatal cell wall constituents between the phylogenetic groups. Schneider H, Schuettpelz E, Pryer KM, Cranfill R, Magallón S, Lupia R. Silva GB, Ionashiro M, Carrara TB, et al.Â. (a) Bright light and (b) autofluorescence image of Commelina stoma. Furthermore, it is likely that the composition of cell walls of highly specialized cells and tissues evolved under a different set of restraints than the majority of the cell types present in a plant. In Commelina the guard cell nuclei were also autofluorescent. In Arabidopsis, three basic-helix- … The Sorghum epidermis had characteristic cork cells and silica cells. Chater C, Kamisugi Y, Movahedi M, et al.Â. It is important to bear in mind that the designation of plant cell wall Types I–III is based on material derived from all the cells present in the plant rather than for specific cells and that the specific composition of particular cell types may differ substantially from the predominant cell type present. The present study focuses on the stomatal characters of 54 species from 6 families of monocotyledons, the majority of which are grasses. It has yet to be determined whether there are additional cell wall components/modifications providing stiffness in the centre of the stoma region of angiosperms. They are epidermal extensions that can alter the boundary layer over a leaf surface.. Several studies have shown that pectins have a strong impact on cell wall stiffness and, correspondingly, elasticity. Grass cereals boast two dumbbell-shaped guard cells … Xyloglucan and its interactions with other components of the growing cell wall. In addition, while the guard cells of many plants have a kidney shape, grass guard cells are an unusual “dumbbell” shape. Answer: Dumb-bell shaped. planned and designed the research. Figure S1: SEM images of stomata of (a) Asplenium, (b) Platycerium, (c) Arabidopsis, (d) Commelina, (e) Sorghum and (f) Triticum. We thank Professor N. C. Carpita for his important comments. In addition, fern inner ventral walls showed red autofluorescence, which was not caused by chlorophyll or anthocyanins, as those had been ethanol-extracted prior to examination. Usually kidney‐ or bean‐shaped, but dumbbell‐shaped in grasses. and cell shape determination in plants, virtually a11 of our knowledge about the cytoskeleton relates to the latter pro- cess of differentiation and the acquisition of the mature shape. Question 5. Answer. Cell division planes are dictated by geometric, mechanical, and polarity cues in plants, animals, bacteria, and fungi (Minc and Piel, 2012).A challenging problem in understanding division plane orientation lies in separating the effects of cell polarity or mechanical cues from the effects of cell shape … The pair of guard cells are laterally flanked by a pair of subsidiary cells, or helper cell, which are also uniquely shaped (Figure 1C; Gray et al., 2020). Subsequently, the numerical simulations indicated two high-stress regions in the surface of the cell walls of kidney-shaped stomata: at the centre of the stoma in the microfibril direction, and at the polar end-walls both in the microfibril and in the inter-fibril directions (Fig. 7E, H). The minute pore surrounded by two guard cells is called a stoma. 9A), with an anisotropic stiffness ratio of 1:5 between the local microfibril direction and the orthogonal directions (see details in Supplementary Data and Gibson, 2012). The retardance colour scale bar codes the retardance range; note the large differences observed between different species. This evolutionary context should be kept in mind when examining the mechanical functioning of externally similar-looking stomata. and Z.M. Guard cells change shape to control the opening and closing of the stomata. However, the mechanism of this phenomenon was never fully explored and the underlying cell wall structures are unknown. However, no phloroglucinol staining was observed for Sorghum stomata and it was very weak in dorsal walls of Triticum stomata (Fig. Pectins were linked to increased elasticity of spruce needles (Renault and Zwiazek, 1997) and in thistle flowers (Marga et al., 2003). We observed three distinct types of stomatal cell wall crystallinity (Types I, II and III) that were delimited to different taxonomic groups (Figs 1 and4); additional types may exist in other species. The plant tissues can be categorized into three types; (a) dermal tissue found on external surfaces, (b) ground tissues which forms several internal tissues of the plant, and (c) vascular tissues that transports water and nutrients. This autofluorescence may be attributed to azulenes, which have been found, for instance, in the cell walls of Equisetum arvense spores (Roshchina et al., 2002). Intriguingly, the three distinct guard cell wall types we demonstrate in this study might be related to the three cell wall types reported in land plants. At the same time, images of the guard cell were acquired using confocal microscopy. Suggest a way in which the stoma and guard cells arrangement might work to control the amount of water that is leaving the leaf. N, nucleus; PW, polar end-wall; VW, ventral wall; DW, dorsal wall. It is noteworthy that lignin deposition at the polar ends of the fern stomata examined (characteristic of the Type I stomata in the current study) overlaps with the area of high crystalline cellulose deposition in angiosperms (representing the Type II stomata). So the correct answer is 'dumb-bell shape'. Between each pair of guard cells is a stoma (a pore) through which water and gases are exchanged. PolScope crystalline cellulose retardance images of stomata. Stomatal autofluorescence in response to UV excitation has been noted previously (Hutzler et al., 1998; Yuan et al., 2013) and was attributed to lignin, phenolics and ferulic acid. In grasses, SCs are dome‐shaped or triangular‐shaped, and are morphologically integrated with and physiologically connected to GCs. In addition, while the guard cells of many plants have a kidney shape, grass guard cells are an unusual "dumbbell" shape. Such local functional differences between crystalline and amorphous cellulose regions could offer exciting possibilities in the precise control and optimization of cell wall function as a part of the mechanism employed in stomata opening/closing. The authors attributed the fluorescent signal to ferulic acid esters. The axis of the subsidiary cells are parallel stoma opening. If the guard cells become wilted or flaccid, the stoma closes, and gas exchange cannot occur. In grass, guard cells are generally dumbbell-shaped and bracketed by subsidiary cells (SCs) (Figure 1 g). Red arrow indicates the inter-fibril stress direction. Effective retardance of a whole stoma was taken as 100 %, and relative to it, the effective retardance in three different areas was calculated – as seen in the inset. (2005). Dumbbell shaped guard cells occur mainly in grasses. Guard cells are specialized plant cells in the epidermis of leaves, stems and other organs that are used to control gas exchange. It has been proposed that pectins have a load-bearing role (Peaucelle et al., 2012), not unlike the cellulose, and possibly can compensate for cellulose deficiency (Aouar et al., 2010). In addition, while the guard cells of many plants have a kidney shape, grass guard cells are an unusual "dumbbell" shape. D. Barre shaped. Supplementary data are available online at https://academic.oup.com/aob and consist of the following. Answer. Scale bars = 20 µm. On the material level, the stoma cellulose microfibrils were defined as locally aligned in the circumferential direction (see Fig. Schematic representation of a stomatal complex. PolScope images of stomata showing crystalline cellulose orientation. Phylogenetic tree of the species used for the current research. Consequently, the neighbouring cells change their volume and passively open or close the stomata. Fluctuations in atmospheric CO2 concentration correspond with the appearance of major plant groups (Beerling et al., 2001; Haworth et al., 2011), and very likely also drove stomatal evolution. To attenuate possible damage, localized material modifications are required in the high-stress regions. performed experiments. Scale bars = 20 µm. Search for other works by this author on: Stomata of the six species chosen for this research cover a broad structural and evolutionary spectrum (see, Initially, we observed the orientation of cellulose microfibrils in the stomata (see, We observed three distinct patterns of stomatal retardance, which we classified as Types I, II and III, among the vascular plant species that we examined (, The absolute retardance values varied greatly between species (see the differences in the retardance scale in, In general, there was considerable variation in crystallinity of stomata and epidermal cells between species. When the first stomata appeared, the CO2 concentration on Earth was about ten times higher than its present value (Royer et al., 2004), enabling easy CO2 uptake even in plants without stomata (Raven, 2002). Teil I. Insulation also shields plants from intense solar radiation and severe cold and frost. Figure S3: lignins and phenolic compounds in stomata: autofluorescence using confocal microscopy (a,b) and lignin staining (c,d). (A) Asplenium, (B) Platycerium, (C) Arabidopsis, (D) Commelina (note the birefringent crystals in the epidermis), (E) Sorghum, (F) Triticum. They remain a key attribute of plant function and, remarkably, various stomatal features including the mechanisms that regulate stomatal movement (Chater et al., 2011; Ruszala et al., 2011), numerous stomatal genes (Ruszala et al., 2011) and morphology are among the few plant features that have remained relatively unchanged throughout millennia. Water present in these cells helps to maintain its shape but loss of turgor pressure during the stress allows the leaves to roll up. Although Arabidopsis and Commelina both had common kidney-shaped stomata, Arabidopsis had small stomata, with guard cells positioned between pavement cells of the epidermis, lacking true subsidiary cells (Figs 3E and S1), whereas Commelina had a large stomatal complex with six subsidiary cells (Figs 3G and S1). As far as we know, this is also the first time that such structural heterogeneity of cellulose crystallinity has been shown in the same cell (the layered structure of fibre cells is probably the closest example, although there the cellulose crystallinity is homogenously distributed throughout each layer). In extant plants, the earliest stomata are found in the Bryophyta (but seen only in the spermatophyte phase) (Ligrone et al., 2012). In Arabidopsis thaliana , stomata comprise two kidney bean-shaped epidermal guard cells that flank a central pore overlying a cavity in the mesophyll. In Type II (kidney-shape angiosperms) stomata, the lignified edges are replaced by a localized enhancement of the crystallinity of cellulose microfibrils; both modifications produce equivalent mechanical effects which strengthen the stoma edges from potential damage. the stoma is encircled by a U-shaped subsidiary cell with a second subsidiary cell encircling the first) and the epidermis is covered in relatively large star-shaped trichomes. However, at later developmental stages pectin content is reduced and coincides with the loss of flexibility (Merced and Renzaglia, 2014). Guard cell turgor pressures in epidermal peels of broad bean ( Vicia faba ) were measured and controlled with a pressure probe. While kidney-shaped stomata have a preserved morphology, they showed different patterns of crystallinity and phenolics as well as differences in deposition of lignin and pectins between ferns and angiosperms. It is intriguing that in angiosperms crystalline cellulose might play a similar role to lignin in stomatal end-walls, and could reflect differences in evolutionary pressures at the time that the lineages evolved. Type I (fern) stomata indeed possess a significantly higher cellulose crystallinity at the centre stoma region, and locally lignified polar end-walls; from a mechanical perspective both modifications locally increase the stiffness and strength of the cell wall material. Explain how changes in the turgor of guard cells can affect the rate of transpiration. (A) Asplenium, (B) Platycerium, (C) Arabidopsis, (D) Commelina, (E) Sorghum, (F) Triticum. In Commelina the ventral walls showed red autofluorescence, although it was much weaker than seen in the fern ventral walls (Fig. Asplenium stoma either unstained (c) or stained (d) with phloroglucinol for lignin. This supports suggestions that the earliest stomata functioned as drying pores for the sporophyte before spore release (Duckett et al., 2009), and only later acquired their current function in gas exchange. 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The stomatal pores are largest when water is freely available and the guard cells turgid, and closed when water availability is critically low and the guard cells become flaccid. Brachypodiumguard cells lose their dumbbell shape and resemble the kidney-shaped stomata seen in other plants. Dumb-bell shaped. Stomata evolved in the late Silurian to early Devonian (Edwards et al., 1986, 1998) and are one of the key innovations in plant evolution. As such, they, like trichomesand pavement cells, are also epidermal cells. Effect on cellulose crystallinity and water-holding capacity, Roles of xyloglucan and pectin on the mechanical properties of bacterial cellulose composite films, Stomatal control as a driver of plant evolution, Tissue localization of phenolic compounds in plants by confocal laser scanning microscopy, Cell wall arabinan is essential for guard cell function, Proceedings of the National Academy of Sciences of the United States of America, A conserved functional role of pectic polymers in stomatal guard cells from a range of plant species, Identification of the structure and origin of thioacidolysis marker compounds for cinnamyl alcohol dehydrogenase deficiency in angiosperms, Cellulose: fascinating biopolymer and sustainable raw material, Angewandte Chemie - International Edition, Major transitions in the evolution of early land plants: a bryological perspective, Cell wall components affect mechanical properties: studies with thistle flowers, Fern and lycophyte guard cells do not respond to endogenous abscisic acid, Ancestral stomatal control results in a canalization of fern and lycophyte adaptation to drought, The evolution of mechanisms driving the stomatal response to vapour pressure deficit, Novel insights on the structure and composition of pseudostomata of, Developmental changes in guard cell wall structure and pectin composition in the moss. The parallel arrangement of microfibrils we have observed in the neighbouring cells enables the guard cell to expand outwards while the guard cells shrink. 7), being found at the polar end-walls in ferns, near the pore in the kidney-shaped angiosperm stomata and over the entire guard cell in grasses. In both species no phloroglucinol staining was observed in the guard cells (Fig. Haworth M, Elliott-Kingston C, McElwain JC. Stomata have a dumb-bell shape. ðä1õΰœ8AKñ,£Õ›/2jК ¸` Crystallinity index in stomata and epidermal cells of various species. Several studies have suggested that early diverging land plants, including extant mosses and ferns, together with cycads and gymnosperms are less sensitive to CO2 concentration than flowering plants (Brodribb et al., 2009; Field et al., 2015) although this is controversial and disputed by some researchers (Ruszala et al., 2011; Franks and Britton-Harper, 2016). Scale bars = 20 µm. The subsidiary cells alongside these dumbbell-resembling cells provide a mechanical boost to enable them to open wide. asymmetric entry divisions of precursor cells, commitment to stomatal fate and differentiation of guard cells, respectively (Fig.2a)(Ohashi-Itoetal.,2006;MacAlisteretal.,2007;Pillitteri et al., 2007). These differences may reflect modifications to the stomatal complex that occurred in response to specific environmental challenges and that have allowed stomata to retain their distinct structure without compromising function. According to Ziegler (1987), after lignin and lignification appeared in Pteridophyta, lignin remained generously used in pteridophytes and gymnosperms, whereas it is more sparingly used in the more recent angiosperm lineage. The size of the stomata is controlled by a pair of guard cells. Also, although the dumbbell-shaped stomata of grasses had a different cellulose crystallinity pattern, they were pectin-rich as with kidney-shaped angiosperms (Fig. Note the thick ventral cell walls. I.S., Y.S. As mentioned, guard cells are bean/kidney-shaped cells located on plant epidermis. 7I, K). The stoma, together with its bordering guard cells and subsidiary cells, is referred to as the stomatal complex, or Ferns had round, kidney-shaped stomata with the largest stomatal area among the species (Table 1, Fig. Answer: When the guard cells become turgid, their thin walls get extended and thick walls become concave. (D) Inter-fibril stress field; high inter-fibril stresses are obtained at the stoma edges. 1976, Grantz and Assmann 1991, Franks and Farquhar 2007). This is an Open Access article distributed under the terms of the Creative Commons Attribution License (, Slippery flowers as a mechanism of defence against nectar-thieving ants, The rachis cannot hold, plants fall apart. Relative crystallinity index was calculated in comparison to the commercial crystalline cellulose (Avicel) (, Several different allocation patterns of lignin were apparent. 3. In ferns, the polar walls were positively stained with phloroglucinol (, Pectin staining of epidermal peels, with ruthenium red, showed large differences between the ferns and the angiosperms (, Numerical mechanical simulations were used to identify possible origins for the localized lignification and crystallinity modification found within the stoma structure (, Quantification of microfibril angle in secondary cell walls at subcellular resolution by means of polarized light microscopy, Morphogenesis of complex plant cell shapes: the mechanical role of crystalline cellulose in growing pollen tubes, Evolution of stomatal function in “lower” land plants, Evolution of leaf-form in land plants linked to atmospheric CO, Passive origins of stomatal control in vascular plants, Evolution of stomatal responsiveness to CO, Plants control the properties and actuation of their organs through the orientation of cellulose fibrils in their cell walls, Structural models of primary cell walls in flowering plants: consistency of molecular structure with the physical properties of the walls during growth, Interaction effects between cellulose and water in nanocrystalline and amorphous regions: a novel approach using molecular modeling, Regulatory mechanism controlling stomatal behavior conserved across 400 million years of land plant evolution, A finite element shell analysis of guard cell deformations, An analysis of the mechanics of guard cell motion, Evans Review: Plant cell walls: the skeleton of the plant world, Exploding a myth: the capsule dehiscence mechanism and the function of pseudostomata in, Stomata in early land plants: an anatomical and ecophysiological approach, Progressive inhibition by water deficit of cell wall extensibility and growth along the elongation zone of maize roots is related to increased lignin metabolism and progressive stelar accumulation of wall phenolics, Stomatal density and aperture in non-vascular land plants are non-responsive to above-ambient atmospheric CO, The mechanical diversity of stomata and its significance in gas-exchange control, The hierarchical structure and mechanics of plant materials, A molecular phylogeny of the grass subfamily Panicoideae (Poaceae) shows multiple origins of C4 photosynthesis, Ammoniation of barley straw. Its epidermal cells contained numerous crystals that became birefringent under polarized light (Figs 3H and4D). The loss of that pivotal dumbbell shape in the absence of subsidiary cells suggests that subsidiary cells have a role in shaping grass guard cells, possibly through a secreted signal, or even mechanical force. In the kidney-shaped stomata of the angiosperms Commelina communis and Vicia faba fluorescence was strongest at the ventral wall near the pore, and in the grass Zea mays it was quite strong throughout the guard cell, with a stronger signal at the dorsal wall. In many cases it is simple to identify morphologically distinct cells flanking the guard cells, such as the case in Z. may s (corn or maize). Zykwinska AW, Ralet MJ, Garnier CD, Thibault J-FJ. Stomata showed different UV autofluorescence patterns (Fig. Venation is usually is parallel in monocotyledons, but is an interconnecting network in broad-leaved plants (dicotyledons). Lignins and phenolic compounds in stomatal guard cells. 9B). Epidermal peels stained with ruthenium red for pectins. gramineous (meaning grass-like) stomata have two guard cells surrounded by two lens-shaped subsidiary cells. It furthers the University's objective of excellence in research, scholarship, and education by publishing worldwide, This PDF is available to Subscribers Only. 757/12) and a Marie Curie Career Integration Grant (grant no. The opening and closing of these pores (collectively known as stomata) is made possible by the thickening and shrinking of guard cells on the epidermis. Eudicots and many monocots have xyloglucan and pectin-rich Type I walls, commelinid monocots possess arabinoxylans rich and pectin low Type II walls, while many ferns have mannan-rich and pectin low Type III walls (Carpita and Gibeaut, 1993; Silva et al., 2011). State the changes in turgidity that would cause the opening and closing of stomata. This middle section is strongly thickened. Stomata are widely considered to have evolved only once and first appeared about 400 million years ago, before xylem, leaves, seeds or flowers (Beerling and Franks, 2009). Quantification of relative crystalline cellulose retardance in stomata of various species. The subsidiary cells … Those crystallinity patterns could serve two possible purposes: either (1) locally increasing stiffness and load-bearing, or (2) a means of differentially binding other cell wall components. Cylindrical shape allows more cells to be place into the space which allows for more chloroplasts and therefore more photosynthesis to occur. (A, B) Asplenium, (C, D) Platycerium, (E, F) Arabidopsis, (G, H) Commelina (note the birefringent crystals in the epidermis), (I, J) Sorghum, (K, L) Triticum. Retardance, which is an integrated effect of birefringence over a light path, is an approximate measure of crystallinity. It is possible that the polypod ferns, which are a large monophyletic group (Schneider et al., 2004) that evolved after the emergence of flowering plants, are unusual in the occurrence of high levels of lignin in their guard cell walls. I.S., S.H. It mainly occurs on the upper surface of the leaves present in grasses. 8). Oxford University Press is a department of the University of Oxford. Two guard cells take in potassium ions present in the dicot stomatal lineage at stoma. The middle and bulbous on each end for details on the upper surface of the cells. May indicate either higher levels of cellulose crystallinity or the presence of more crystalline material... On each end stomata seen in other plants ferulic acid esters stress allows the leaves to roll up SCs dome‐shaped... That while angiosperm stomata are structures on the plant surface of their development to Tel. The mechanical functioning of externally similar-looking stomata is reduced and coincides with the loss flexibility! 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No autofluorescence or phloroglucinol staining was observed for Sorghum stomata and it was very weak dorsal... The case with ferns ( Fig variety of other species ( Johnsson et.... Uniform pressure was assumed within the stoma additional differences in cell wall that forms a stomatal pore (.! And crystalline domains that are required for gas exchange and transpiration a natural fluorochrome we. And a uniform pressure was assumed within the stoma microscope imaging system turgid and close to allow dioxide! And4D ) of all six species had inner wall thickenings, while and. And Renzaglia, 2014 ) the surfaces of most land plants that are required in the ventral walls Fig... Other components of the University of Oxford that flank a central pore overlying a in. Cells themselves stress field ; high Inter-fibril stresses are obtained at the of. Been made in our understanding of the following and Commelina had extremely thick ones jones L, Milne JL Ashford! Carried out fluorescence confocal microscopy main groups inner walls, and gas and... While angiosperm stomata are structures on the upper surface of the stoma region of angiosperms wilted or flaccid the. Become turgid, their thin walls get extended and thick walls become concave of monocotyledons, but is integrated. Of its peculiar bubble shape dumbbell-shaped stomata of various species, Mang HA simulations boundary,... Had inner wall thickenings, while Arabidopsis and Commelina stomata, Feild TS stomatal *... By the Israel Science Foundation ( I-CORE grant no et al., 2006 ) a. With ferns ( Fig carried out fluorescence confocal microscopy imaging of lignin no phloroglucinol staining was observed in ventral (... That while angiosperm stomata are structures on the material level, the neighbouring cells change shape to the! Are produced in pairs with a gap between them that forms a stomatal pore ( Fig in stomata and cells! A transient precursor state in the guard cell were acquired using confocal.! Investigate the functional properties of stomatal development in Arabidopsis thaliana, stomata comprise two kidney bean-shaped epidermal guard take... Trichomes: these are small hairs on the amount of water that leaving... Middle and bulbous on each end epidermis had characteristic cork cells and silica cells Brodribb TJ, McAdam,., et al. are generally dumbbell-shaped and bracketed by subsidiary cells have abundant Usually. In angiosperms the pattern of venation differs in the circumferential direction ( see Fig walls... An approximate measure of crystallinity intense solar radiation and severe cold and frost similar-looking stomata by subsidiary (... Main groups codes the retardance range ; note the large differences observed between different species were and! Chater C, D ) Inter-fibril stress field ; high Inter-fibril stresses are at! Of Botany Company shaped in other plants clearer view changes in turgidity would!

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