Biological Sciences
Stomata
Stomata are small pores found on the surface of plant leaves and stems that regulate gas exchange and water loss. They open to allow carbon dioxide to enter for photosynthesis and close to minimize water loss through transpiration. Stomata play a crucial role in maintaining the balance between carbon dioxide uptake and water conservation in plants.
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11 Key excerpts on "Stomata"
eBook - PDFPlants and Microclimate
A Quantitative Approach to Environmental Plant Physiology
- Hamlyn G. Jones(Author)
- 2013(Publication Date)
- Cambridge University Press(Publisher)
6 Stomata Contents 6.1 Distribution of Stomata 6.2 Stomatal mechanics and mechanisms 6.3 Methods of study 6.4 Stomatal response to environment 6.5 Stomatal resistance in relation to other resistances 6.6 Stomatal function and the control loops 6.7 Sample problems The evolution of the Stomatal apparatus was one of the most important steps in the early colonisation of the terrestrial environment. Even though the Stomatal pores when fully open occupy between about 0.5 and 5% of the leaf surface, almost all the water transpired by plants, as well as the CO 2 absorbed in photo- synthesis, passes through these pores. It is only in rare cases, such as in the fern ally Stylites from the Peruvian Andes, that significant CO 2 may be absorbed through the roots (Keeley et al., 1984). The central role of the Stomata in regulating water vapour and CO 2 exchange by plant leaves is illustrated in Figure 6.1. This figure also shows some of the complex feedback and feedforward control loops that are involved in the control of Stomatal apertures and hence of diffusive conductance; these are discussed in Section 6.6.1. It is the extreme sensitivity of the Stomata to both environmental and internal physiological factors that enables them to operate in a manner that optimises the balance between water loss and CO 2 uptake. This chapter outlines the fundamental aspects of Stomatal physiology, their occurrence in plants, their morphology, their response to environmental factors and mechanics of operation, including a description of the various control loops illustrated in Figure 6.1. The role of the Stomata in the control of photo- synthesis and of water loss is discussed in more detail in Chapters 7 and 10. Further information on Stomata, their responses and mechanism of operation, may be found in older texts or symposia such as those by Meidner and Mansfield (1968), Jarvis and Mansfield (1981), Zeiger et al.
eBook - PDF- Sunil Pareek(Author)
- 2016(Publication Date)
- CRC Press(Publisher)
However, the leaves of the high-temperature-developed plants possess lower Stomatal density and reduced Stomatal size. In this case, to cool down the leaf, plant architec-tural adaptions such as petiole elongation, leaf elevation above the soil, and decrease in leaf thickness enhanced the diffusion of water vapor from the Stomata (Crawford et al., 2012; Murata and Mori, 2013). As another role of Stomata, it is generally accepted that the tran-spirational flux is the main mechanism of transport of nutrients in plants (Mengel and Kirkby, 1982; Novák and Vidovic ˇ, 2003). 6.2.2 Mechanism of Stomatal Closure and Opening Closure and opening of the Stomata pores depend on many factors, including environmental factors such as light, temperature, and RH (or better water VPD), CO 2 concentration inside the Stomatal cavity, water availability, and pathogens, and endogenous factors such as phytohormones and their inter-actions, and secondary messengers. Stomatal aperture changes over diur-nal cycles. To facilitate CO 2 assimilation, Stomata stay open during the day, especially in response to blue light, and tend to be closed at night (Talbott and Zeiger, 1998; Schroeder et al., 2001; Tallman, 2004). However, to con-serve water, plants with a crassulacean acid metabolism (CAM) close their Stomata during the daytime and open at night to uptake CO 2 (Bohnert et al., 1995; Black and Osmond, 2005). In this way, CAM plants lose less water and are adapted to dry conditions. The number of Stomata over the leaf surface is species dependent (Table 6.1) and highly depends on the environmental 162 P O S T H A R V E S T R I P E N I N G P H Y S I O L O G Y condition prevalent during growth of the plants. The distribution of Stomata over the leaf surface is not a random process. They are distributed in a way that effective diffusion of the gases between leaf internal tissues and the surrounding environment is provided.
eBook - PDFPlant Physiology 9
A Treatise: Water and Solutes in Plants
- F.C. Steward(Author)
- 2012(Publication Date)
- Academic Press(Publisher)
IX: Water and Solutes in Plants Copyright © 1986 by Academic Press, Inc. All rights of reproduction in any form reserved. 155 1 5 6 T . A. MANSFIELD 3. T H E PHYSIOLOGY OF Stomata 157 to the environment are of central importance in the physiology of guard cells. It is through these reactions that Stomata exert the fine control of gas exchange that is so essential to the survival of the majority of land plants. Furthermore, it is the complexity of these environmental responses that presents the main challenge to the physiologist today, just as in 1959. The emphasis in this chapter remains, therefore, much the same as in Heath's but no attempt has been made to cover all the important literature prior to 1959. The reader is strongly advised to refer to Heath's chapter to gain a full understanding of the many significant earlier researches into the re-sponses of Stomata. Heath expressed the hope that his chapter would . . . serve to indicate the complexity of such an apparently simple matter as a turgor-operated cell movement and hearten research workers at-tracted to this field with the conviction that all is not discovered. The reader of this present chapter may feel that the main achievement of the past 25 years is nothing more than a strengthening of this conviction. If this is the case, then our efforts have not been in vain. We can now claim F IG . 1. An electron micrograph of a Stomatal complex of timothy grass, Phleum pratense L . The Stomatal complexes of graminaceous species such as timothy consist of two guard cells (GC) and two flanking subsidiary cells (SC). The guard cells are bone shaped at maturity, with a narrow, constricted midzone and swollen, bulbous ends. The pore (P) between them is long and slitlike. The guard cell nucleus (N) is elongate and traverses the constricted midzone of the cell. Each guard cell contains many mitochondria (Mi) and plastids (PI). Although internal membranes are present in the latter, grana are not well developed.
eBook - PDF- M. K. V. Carr(Author)
- 2018(Publication Date)
- Cambridge University Press(Publisher)
13 Pores for Thought Gaseous Exchange Wight (1938) described the structure and function of the leaves of a tea plant 80 years ago when working in Assam. In one square inch (645 mm 2 ) of the leaf surface he found, for example, that there were between 10,000 and 20,000 Stomata, small pores which in tea are present only on the lower surface of the leaf (Figures 13.1 and 13.2). In fact, these numbers are a factor of 10 out (Box 13.1). There are 100,000–200,000 in a square inch (equivalent to 155–310 Stomata mm −2 ). It’ s a lot, anyway! Wight emphasised the role of Stomata in controlling the loss (egress) of water vapour from the leaf through the pores into the surrounding air (a process we know as transpiration), and the entry (ingress) of carbon dioxide (CO 2 , a gas) into the leaf. On entering the leaf, the CO 2 dissolves in the water saturating the cell walls surround- ing the intercellular spaces adjacent to the pore. The CO 2 then passes in solution from cell to cell until it reaches the palisade cells, where, in the presence of chlorophyll and under the influence of sunlight, the process of photosynthesis occurs. The CO 2 combines with the elements of water (hydrogen and oxygen) to form a sugar. For every unit volume of CO 2 taken in by the leaf, an equal volume of oxygen is released. This process, which as Wight (1932) stated allows plants to ‘feed themselves’, also serves to purify the atmosphere for animals, since we breathe in oxygen and expire carbon dioxide. Although they may seem far removed from practical issues arising on a tea estate, fundamental studies of Stomatal behaviour, photosynthesis, transpiration and plant water status are important for helping us to understand the mechanisms responsible for the observed responses of tea to its environment.
- C. B. Johnson(Author)
- 2013(Publication Date)
- Butterworth-Heinemann(Publisher)
13 REGULATION OF GAS EXCHANGE IN WATER-STRESSED PLANTS T. A. MANSFIELD J. A. WILSON Department of Biological Sciences, University of Lancaster, UK Introduction The control of transpiration by the movements of Stomata has an obvious bearing on crop productivity, because as Stomata close to conserve water they increasingly restrict the rate of entry of C0 2 into the leaf for photosynthesis. Water conservation is not only necessary for plants that are suffering measurable water stress. It must be looked upon as a continuous process that requires responses of the Stomata to many factors, which together control the rate of transpiration even in plants which may apparently have an abundant supply of soil water. The occasions are rare when a plant can support the transpiration that occurs through fully open Stomata, which allow a rate of evaporation nearly as great as that from a free water surface of the same area as the leaf. So little water is held in reserve in mesophytes that a leaf which transpires at a rate greater than the replacement of water via the xylem may not survive more than a few minutes, as can be demonstrated by the use of simple treatments to cause Stomata to open to abnormally wide apertures (Mansfield and Davies, 1981). The subject of this paper has to be cgnsidered in the context of all the factors that have been recognized as important in regulating the apertures of Stomata. We have elsewhere suggested that it is convenient to look upon the responses of Stomata as representing different lines of defence (Davies, Mansfield and Orton, 1978; Mansfield and Davies, 1981). The first lines of defence were considered to be the responses to factors of the aerial environment, especially water vapour pressure deficit (VPD) and C0 2 concentration, which can bring about the adjustment of Stomatal apertures to a level appropriate for the prevailing conditions.
eBook - PDF- Emea, A(Authors)
- 2018(Publication Date)
- Agri Horti Press(Publisher)
Neither do all of them close at the same time. Under most conditions, however, This ebook is exclusively for this university only. Cannot be resold/distributed. 202 Plant Physiology : Theory and Practice stomates probably are more nearly coincident in the time of their opening than in the time of their closing. The aggregate diffusive capacity of all of the stomates on a plant must therefore be thought of in terms of the two factors of the degree of opening of the individual stomates and the number of stomates that are open. It is probable that the Stomata1 mechanism of every species of plant exhibits certain distinctive features in the way in which it reacts to various combinations of environmental factors; hence only broad generalizations can be formulated regarding the daily periodicity of Stomata1 behaviour. The results of a number of investigators indicate that as a rule, under the conditions prevailing on a standard day, the stomates of most mesic species of plants are open all or most of the daylight period and closed at night their maximum diffusive capacity being attained about midday, or little before. The stomates open in the morning under the influence of the light factor and soon attain nearly their maximum diffusive capacity. Under standard day conditions, however, the water content and turgor of the leaf cells usually decrease progressively during most of the daylight period. Because of this internal water deficit which develops in the leaf, Stomata1 closure usually begins about noon or a little before. Virtually complete closure of the stomates often takes place considerably before the advent of darkness because of the predominant effect of the water factor over the light factor during the afternoon hours. Innumerable other types of daily cycles of Stomatal behaviour are possible,a few of which will be described briefly.
- T.T. Kozlowski(Author)
- 2012(Publication Date)
- Academic Press(Publisher)
He found that iso-lated Stomata of Amaryllis opened when immersed in water and closed in sugar solutions. These observations have been repeated by many investi-gators. They were supported by direct measurements of the osmotic poten-tial in guard and adjacent cells (e.g., Sayre, 1926) and by the direct experi-ment of Heath (1938) who showed that puncturing a guard cell led to its immediate closure and puncturing an adjacent cell to wider opening. This approach is being currently extended by H. Meidner (private commu-nication), who is able to open and close Stomatal pores by directly increas-ing or decreasing the hydrostatic pressure within the guard cells. [Some observations have now been published by H. Meidner and M. Edwards (1975). This important paper indicates that the hydrostatic pressures applied to guard and subsidiary cells needed to cause given changes in aper-ture were appreciably less than those expected from plasmolytically deter-mined osmotic potentials.] The only alternative hypothesis yet advanced, i.e., that Stomata are deformed by the differential swelling of various layers of the guard cell wall (Nadel, 1935), has little support. There is over-whelming evidence that an increase in the concentration of osmotically active substances within the guard cells leads to a decrease in the chemi-cal potential of the contained water and, hence, to a net influx of water, thereby increasing the volume of the guard cell and opening of the pore. 2. Structure and Functioning of Stomata 75 7 . Water Relations of Guard Cells In this chapter, we follow the usual convention of representing water potentials (Slatyer and Taylor, 1 9 6 0 ) .
eBook - ePub- Matthew A. Jenks, Paul M. Hasegawa, Matthew A. Jenks, Paul M. Hasegawa(Authors)
- 2013(Publication Date)
- Wiley-Blackwell(Publisher)
3 Stomatal regulation of plant water statusYoshiyuki Murata1 and Izumi C. Mori21 Graduate School of Environmental and Life Science, Okayama University, Tsushima-Naka, Kita-Ku, Okayama, Japan2 Institute of Plant Science and Resources, Okayama University, Chuo, Kurashiki, Okayama, Japan3.1 Stomatal transpiration and cuticular transpiration
The gametophytes of mosses and liverworts do not possess true Stomata. Instead of Stomata, liverwort gametophytes possess air pores. In contrast, most of the sporophyte generations of the bryophytes possess Stomata (Zeigler, 1987). Lichens that have wider ecological realms than the bryophytes are completely astomatous. The Isoetaceae have a number of astomatous species, particularly in the genus Isoetes . Most astomatous species of Isoetes are aquatic, and some phanerogam species become astomatous when submerged, for example, Lobellia dortmanna (Pedersen and Sand-Jensen, 1992) and species of Ranunculus (Bruni et al., 1996). However, some species of Isoetes and Stylites are terrestrial, occurring around the edges of oligotrophic bogs, and are astomatous (Keeley et al., 1984, 1994). It has been argued that Stomata are either absent or non-functional in species with plastic responses to submergence where gaseous exchange through Stomatal pores does not occur; instead gaseous movement through aerenchyma is the norm (Sculthorpe, 1967; Raven, 1984). Stomata are completely afunctional in the parasitic orchid, Neottia nidus-avis (Ziegler, 1987). Stomata are incapable of opening in Neottia , since the guard cells are fused to each other. In contrast, the Stomata in some aquatic species, such as Nymphaea alba , Nuphar lurea , and Lemna minor , remain permanently open (Ziegler, 1987). In L. minor , the Stomata do not close because the guard cells are mortal. In Nymphaea and Nuphar
eBook - PDF- F. R. Whatley, M. J. Kozioł(Authors)
- 2016(Publication Date)
- Butterworth-Heinemann(Publisher)
The inner walls of the epidermal cells which are adjacent to the Stomatal pore are thought to represent major evaporation sites within leaves (see Figure 2.1 of Meidner and Sheriff, 1976). This is because the diffusion paths of least resistance between the subStomatal cavity and the atmosphere are those from cells closest to the pore. The 136 The role of Stomata in resistance mechanisms converse will apply to S 0 2 entering from the atmosphere: once a molecule has entered through a stoma the route to the surface of a nearby subsidiary or epidermal cell is very short. The cells of the epidermis are therefore in a vulnerable position. They may also be more susceptible to S 0 2 injury because they lack chloroplasts (epidermal cells of higher plants only rarely contain chloroplasts). This could deprive them of the ability to convert S 0 2 to H 2 S using energy from photosynthetic electron transport. Sekiya et al. (1981) have reported that H 2 S emission from cucurbit leaves is almost totally light dependent. Cells without chloroplasts may therefore lack an important detoxification mechanism for removing excess sulphur by the production of H 2 S , and its diffusion back into the atmosphere. The ability of S 0 2 to damage epidermal and subsidiary cells preferentially can thus produce Stomatal opening by a simple mechanical means, namely the reduction of the pressure normally imposed upon the guard cells by the turgor of their neighbours. This leads to wider Stomatal apertures during the day, though does not necessarily impair their ability to respond to stimuli such as light and C 0 2 . Consequences of enhanced Stomatal opening Biscoe, Unsworth and Pinckney (1973) estimated that the Stomatal opening responses to S 0 2 which they had observed in broad bean would increase transpiration of a field crop by 23%. This could obviously be of economic significance since the supply of soil water often imposes limitations on productivity.
eBook - PDFElevated Carbon Dioxide
Impacts on Soil and Plant Water Relations
- M.B. Kirkham(Author)
- 2016(Publication Date)
- CRC Press(Publisher)
The letters in the figure refer to the pages, cited in the lower right of the figure, that discuss the various factors controlling Stomatal movements. These pages are in the article by Heath and Mansfield from which this figure has been taken. (Reprinted from Heath, O.V.S. and Mansfield, T.A, The movements of Stomata, in Wilkins, M.B., Ed., The Physiology of Plant Growth and Development , McGraw-Hill, New York, 1969, pp. 301–332, Fig. 9.9, Copyright 1969, McGraw-Hill, with permission from T.A. Mansfield, Lancaster University, Lancaster, United Kingdom, and Malcolm B. Wilkins, Regius Professor Botany, Glasgow, United Kingdom.) Elevated Atmospheric Carbon Dioxide: Stomatal Conductance 151 © 2011 by Taylor & Francis Group, LLC that guard cell turgor is increased and Stomata open. A negative shows that guard cell turgor is decreased and Stomata close. Under non-stressed conditions, Stomata of plants with the C 3 and C 4 type of photosynthesis are open during the day and closed at night (de Willigen et al. 2005). Stomata of plants with the CAM (Crassulacean acid metabolism) type of photosynthesis are open at night and are closed dur-ing the day. They open in the dark in response to a reduction in CO 2 concentration, and, thus, in CAM species, chloroplast photosynthesis is not required for Stomatal opening (Von Caemmerer and Griffiths 2009). The one commercially important plant with the CAM type of photosynthesis is pineapple ( Ananas comosus Merr.). Some Stomata of C 3 and C 4 plants are “leaky” at night, and these plants have nocturnal water loss, like CAM plants (Green et al. 2006). But we shall not con-sider this topic here. Now, let us look in more detail at the factors that control Stomatal movements, not yet consider-ing elevated CO 2 . S TOMATAL O PENING For over a 100 years, it has been known that guard cells take up potassium (Macallum 1905). In the mid part of the twentieth century, Japanese workers studied potassium in guard cells.
eBook - PDF- Alan R. Hemsley, Imogen Poole(Authors)
- 2004(Publication Date)
- Academic Press(Publisher)
In: Sage RF, Monson RK, eds. C 4 Plant Biology . San Diego: Academic Press, 411–444. Kerstiens G. 1996. Diffusion of water vapour and gases across cuticles and through Stomatal pores presumed closed. In: Kerstiens G, ed. Plant Cuticles – an Integrated Functional Approach . Oxford: BIOS Scientific Publishers, 121–134. Kirschbaum MUF, Gross LJ, Pearcy RW. 1988. Observed and modelled Stomatal responses to dynamic light environments in the shade plant Alocasia macrorrhiza. Plant, Cell and Environment 11 : 111–121. Knapp AK, Smith WK. 1987. Stomatal and photosynthetic responses during sun/shade transitions in subalpine plants: influence on water use efficiency. Oecologia 74 : 62–67. Knoll AH. 1984. Patterns of extinction in the fossil record of vascular plants. In: Nitecki MH, ed. Extinctions. Chicago: University of Chicago Press, 21–68. Kürschner WM. 1996. Leaf Stomata as biosensors of paleoatmospheric CO 2 levels. LLP contribu-tion. Series 5 , 1–153. Kürschner WM, Wagner F, Visscher EH, Visscher H. 1997. Predicting the response of leaf Stomatal frequency to a future CO 2 -enriched atmosphere: constraints from historical observations. Geologische Rundschau 86 : 512–517. Lake JA, Quick WP, Beerling DJ, Woodward FI. 2001. Signals from mature to new leaves. Nature 411 : 154. Lawson T, James W, Weyers JDB. 1998. A surrogate measure of Stomatal aperture. Journal of Experimental Botany 49 : 1397–1403. Lawson T, Weyers JDB. 1999. Spatial and temporal variation in gas exchange over the lower sur-face of Phaseolus vulgaris primary leaves. Journal of Experimental Botany 50 : 1381–1391. Lawson T, Oxborough K, Morison JIL, Baker NR. 2002. Responses of photosynthetic electron transport in Stomatal guard cells and mesophyll cells in intact leaves to light, CO 2 and humidity. Plant Physiology 128 : 52–62. Lee J, Bowling DJF. 1993. Influence of the mesophyll on Stomatal opening. Australian Journal of Plant Physiology 22 : 357–363. Leuning R, Kelliher FM, De Pury DGG, Schulze ED. 1995.
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