Stomata and CO2

Your opinion ?




To me, the modern world is largely a product of the Enlightenment – the European intellectual movement that emerged in the late 17th and 18th centuries and that emphasizes reason, progress and individualism rather than tradition. During this period humanity made great strides in defining the scientific method and technological progress, ethical behaviors and democratic social structures. We see the ongoing fruits of these ideas all around us today in the huge improvements in the quality of life that ever more people have enjoyed in the last few centuries.

These dramatic improvements in human living conditions have not come without significant costs, and rising atmospheric CO2 levels is one existential concern. The resulting global warming is here for all to see, and in my view only the most ignorant Luddites imaginable can deny it – people with no understanding of the ideas of the enlightenment. It is simply a scientific fact that atmospheric CO2 levels have risen by 44% since the early 1800s and the only plausible explanation is that this change results from human actions; the burning of fossil fuels and so on.

I recently learned that this atmospheric change is actually doing more than raising global temperatures and thus affecting the ice caps, sea levels and weather patterns. Plants use photosynthesis, whereby water drawn up through their root systems combines with CO2 drawn in from the atmosphere, to create the carbohydrates needed to increase their body mass, with oxygen given off as a waste product. Plant stomata (pores) open to facilitate this reaction – the open pores draw up water from the roots where it transpires to the atmosphere. The open pores also let in CO2 for photosynthesis to occur.

It has been scientifically proven that higher concentrations of CO2 in the air allow photosynthesis to progress faster so that plants grow faster and transpire less water. This can increase plant growth by 20%-60%. Unfortunately, the resulting plants are poor in nutrients (Iron, Phosphorus, other minerals and, especially, Nitrogen) because these are drawn from the soil and into plant tissues by the transpiring water and in the presence of excess CO2 plants transpire about 20% less water.

From our perspective, the biggest problem is Nitrogen deficiencies in plants. All herbivorous and omnivorous animals (including people) need to eat plants containing Nitrogen to be able to convert the carbohydrates they are made up of into amino acids, which are the major constituent of animal body tissues. To counter the reduced water transpiration by plants in CO2 rich environments you need to raise soil Nitrogen levels, which can be done by adding fertilizers or by planting (and eating) more legumes. Legumes, which are particular kinds of plants, exist symbiotically with bacteria called Rhizobia in their root systems which have the ability to absorb atmospheric Nitrogen and allow it to be easily taken up by the plant during transpiration. Therefore, legumes are especially rich in Nitrogen even at low water transpiration rates and so are exceptionally good animal feedstock.

So, rising atmospheric CO2 levels creates many more problems than just warming the atmosphere. The natural world has had billions of years to develop incredibly complex and interdependent systems (unless you are a creationist who believes the world was created 4,000 odd years ago by some super-being without leaving any supporting scientific evidence). These systems are often finely balanced and small changes can lead to dramatic shifts in equilibrium. Our world will continue to exist until the Sun eventually explodes or shrivels up from a lack of Hydrogen, but if we mess too much with the current equilibrium state, it will dramatically shift to another equilibrium state that does not support Homo Sapiens – this has happened many times in the past, just think asteroids and dinosaurs.


Ontogenetic types of stomata with figures



A new classification of the ontogenetic types of stomata

by Fryns-Claessens E., Van Cotthem W. R. J.  (1973)

Elisabeth Fryns-Claessens, University of Ghent, Belgium

2011-09-30 P1050982_2_2 copy
Willem R. J. Van Cotthem, University of Ghent, Belgium


in The Botanical Review (1973) – 39(1):71-138 – DOI: 10.1007/BF02860071

See full text: ResearchGate


The compilation of new data on stomatal ontogeny from the literature and the finding of a rather unknown type in Marcgravia have shown the need of a new classification of the ontogenetic types of stomata.

Pant (1965) recognized 10 main types; this number is now enlarged to 26 and a modified terminology is chosen. From the name of each type not only the ontogenetical pattern but also the morphological nature of the adult stoma can be deduced. Thus the gap between morphological and ontogeneticalclassifications has been bridged.

Two important differences from Pant’s classification and definitions are introduced.

In this classification any other new type can be included; all the possibilities for the introduction of supplementary data are left open.

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Two important differences from Pant’s classification and definitions are introduced: l. a modification of the definition of the mesoperigenous type ( by incorporation of the possibility that more than one neighbouring or subsidiary cell may be mesogenous). 2. the splitting up of the mesoparacytic type into a para-mesoperigenous and a para-mesogenous type ( not all the surrounding cells in the former being mesogenous). It is well known that any one type of adult stoma can be formed in different ontogenetic ways. This is expressed in our classification for the following cases: 1. aperigenous and anomo-mesoperigenous development for anomocytic stomata; 2. diperigenous, para-mesoperigenous and para-mesogenous development for paracytic stomata; 3. dia-mesoperigenous and dia-mesogenous development for diacytic stomata; 4. cyclo-perigenous, cyclo-mesoperigenous and cyclo-mesogenous development for cyclocytic stomata; 5. aniso-mesoperigenous and aniso-mesogenous development for anisocytic stomata; 6. monoperigenous and hemipara-mesoperigenous development for hemiparacytic stomata. It might be possible to find other examples in the future. The distinction between the aperigenous and the anomo-mesoperigenous type can be difficult. In the latter the stomata! initial divides into 2 unequal cells of which the smaller acts as the g.m.c. or divides a second time before forming the two guard cells. In the aperigenous type the stomata! initial acts directly as the g.m.c. and divides into two guard cells. The difficulty thus lies in the fact that in both types anomocytic adult stomata are produced, so that one has to determine in the first place which cell should be called the “stomata! initial” or “meristemoid,” for this is itself formed by a preliminary division of a protodermal cell. One of the best examples of this difference in interpretation is given in the paper by Bir, Rajagopal & Ramayya ( 1971 ) on the stomata in Rubiaceae. These authors found two developmental patterns for the paracytic stomata and called them: trilabrate and dolabrate. It seems not at all impossible that in both patterns the first division described is one of a protodermal cell and not of a meristemoid as the authors term it. A point in favour of this supposition is the fact that the larger daughter cell of this first division develops into a normal epidermal cell ( neighbouring cell), while the smaller retains its meristematic activity and produces two parallel subsidiaries ( see also Pant & Mehra, 1965: 307 and our comment on it p. 117). Much work remains to be done on stomata and their ontogeny. In our classification all the possibilities are left open to introduce any other new type. One needs only to compose the name of the new ontogenetic type by adding the name of one of the main ontogenetic groups to that of the type of adult stomata involved. New data on the distribution of the known types among the different plant groups, families, genera or species can be added to the list given at the end of the discussion for each type. In order to be able to complete our lists of existing data on the distribution of the types, we invite all research workers to send us reprints of publications on stomata. Any comments on this paper will be gladly accepted and will lead to interesting discussions.

The predominance of hypostomatous leaves over hyperstomatous ones



The adaptive significance of stomatal occurrence on one or both surfaces of leaves

by Parkhurst D. F. (1978)

David F. Parkhurst,

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in Journ. of Ecology 66: 367-383 –


(1) The relationship of stomatal occurrence (on one or both sides of leaves to environment was studied by literature search, mathematical modelling and investigation of herbarium specimens. The starting hypothesis, that hypostomatous leaves (with stomata only on the underside) should occur in dry habitats, was contradicted by all three sources.
(2) The models, based on mass-transfer physics, produced three major results:
(a) mesophyll thickness is the chief variable determining stomatal distribution, with thick leaves tending to be amphistomatous (with pores on both sides);
(b) stomatal distribution does not depend much on environmental variables, but the dependence is strongest under conditions of low water stress;
(c) within the limits of the models, amphistomatous leaves appeared nearly always to be better adapted than hypostomatous leaves, indicating that the models are not yet complete.
(3) Leaf thickness and stomatal distribution were determined from herbarium specimens of the Indiana species of Compositae, Liliaceae, Salicaceae and Scrophulariaceae. These measurements were then compared with a simple habitat rating derived for each species from published habitat descriptions. Hypostomatous leaves occurred least often in xeric habitats, most often in mesic ones, and again less often in hydric habitats. However, the data suggest that this relationship is secondary, with leaf thickness being the intervening variable.
(4) Finally, explanations are considered for the predominance of hypostomatous leaves over hyperstomatous ones


Causes and Ecological Significance of Stomatal Frequency



On the Causes and Ecological Significance of Stomatal Frequency with Special Reference to the Woodland Flora

by Salisbury E. J. (1927)

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in Philosophical Transactions of the Royal Society of London: Biological Sciences, 216, 1-65 –

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by Croxdale J. (2001)

Judith Croxdale,


in Encyclopaedia of Life Sciences – Nature Publishing Group, 1-5 – –


Stomata are specialized cells which respond to environmental and endogenous signals and change shape to allow gas exchange.

The cells are structurally adapted for movement that occurs as the result of increasing osmotic potential and turgor pressure.

Stomata in floating leaves

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Figures 35-43. Broad-leaved monocotyledons. Figure 35. Potamogeton nodosus (× 28). Figure 36. Boottia eordata (× 45). Figure 37. B. eordata (× 0.3). Figure 38. Limnobium spongia (× 15). Figure 39. L. spongia (× 0.8). Figure 40. L. spongia (× 0.08). Figure 41. Hydrocleis nymphoides (× 45). Figure 42. H. nymphoides (× 1.2). Figure 43. H. nymphoides (× 0.1).ves


Anatomical Observations on Floating Leaves

by Kaul R. B. (1976)

Robert B. Kaul

School of Life Sciences, University of Nebraska-Lincoln, Lincoln, Nebraska, USA


in Aquatic Botany 2: 215-234 –


An examination of 24 genera of aquatic plants having floating leaves and leaf-like thalli has been made.

Functional stomata occur on the adaxial sides of floating leaves of angiosperms and some ferns, and in some floating leaves there are stomata on the abaxial surface as well.

Most floating leaves have prominently chambered mesophyll, and in some instances the chambers are locally enlarged and form buoys.


The most consistent anatomical innovations have been the development of functional stomata on the adaxial surface and, in most taxa, the formation of the chambered mesophyll. These innovations have occurred independently in the transition to the floating-leaved condition by distantly related taxa. In some groups, e.g. Gramineae and Sparganiaceae, these characteristics were present in the aerial leaves of the forms ancestral to the floating-leaved species.

The densities of stomata on the adaxial sides of floating leaves vary greatly, just as they do on the abaxial sides of aerial leaves. It is likely that the frequency of stomatal opening is at least as significant as stomatal density. It is known that stomatal frequency and position are greatly influenced by leaf development above, on, or in the water in Polygonum (Massart, 1902), Potamogeton (Shinobu, 1952), and Ranunculus (Sculthorpe, 1967). The presence of some stomata, whether functional or not, on the lower surface of some floating leaves may be viewed as an intermediate condition in the transition from the aerial habit, while the complete absence of stomata in most submersed leaves, at least some of which have evolved from floating leaves, is then the final product of this evolutionary sequence. Floating leaves which have been derived from submersed leaves are likely to have no stomata at all on their abaxial sides, but the evidence for this derivation is at present meager.


Ontogeny of paracytic stomata



Ontogeny of the paracytic stoma: Variations and modifications

by Farooqui P. (1982)

  • Parveen Farooqui, Department of Botany, The University, Allahabad, India


in Proc. Indian Acad. Sci. (Plant Sci.) 91: 145 –


It was generally believed that the topography of the cells surrounding the guard cells in the mature condition indicate their mode of development. However, it has now been established that more than one ontogenetic type may correspond to a single mature type, or it may lead to the development of varied stomatal types.

The paracytic stoma was studied from this viewpoint. It was found that it may be formed through one of at least eight different modes. These are classified and reviewed.

The need to undertake studies on the ontogeny of this type of stoma in various groups of plants has been emphasized.