The Stomata as a Hydrophotic Regulator of the Water Deficit of the Plant

Stålfelt, M. G.

doi:10.1111/j.1399-3054.1955.tb07753.x

Cited by 119 publications

(34 citation statements)

References 20 publications

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“…Addition of mannitol in a concentration of 10"^ M proved to be necessary to enable the stomata to respond 'normally' to factors such as light and darkness and changes in CO2 concentration (a 'normal' response being defined as one similar to that observed on intact leaves). Stalfelt (1955) has shown that over-hydration can lead to a reduction in stomatal aperture and this may have been the factor involved here, although if so it is surprising that the osmotic pressure produced by such a low concentration of mannitol was sufficient to overcome Stalfelt's 'sub-optimal water deficit'. This question is being investigated further, and meanwhile for the present work io~^ M mannitol was added in order to ensure 'normal' behaviour of the stomata.…”

Section: Methodsmentioning

confidence: 91%

Stomatal Behaviour Following Treatment With Auxin‐like Substances and Phenylmercuric Acetate

Mansfield

1967

New Phytologist

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SUMMARYThe 'synthetic auxins' 2-naphthoxyacetic acid (XOXA), i-napththylacetic acid (XAA) and 2,4-dichlorophenoxyacctic acid (2,4-D) caused stomatal closure when apphed to detached leaves via their petioles. In the case of NOXA and XAA this closure was readily reversed if the intercellular spaces were flushed with CO,-free air, but the closure due to 2,4-D was not reversed by such treatment. It is concluded' that XOXA and NAA cause stomatal closure by disturbing the CO, balance in the leaf (by stimulating respiration or inhibiting photosynthesis) whereas 2,4-D exerts a more direct efl^ect on the guard cells.Phenylmercuric acetate (PA I A) caused stomatal closure on strips of detached epidermis, and this could be prevented by CO,-free air during the first 2 hours of treatment. Subsequently closure did occur in CO^-free air but by this time the toxicity of PAIA had apparently led to death of the cells. The relevance of these observations to the idea that chloroplast volume changes participate in the stomatal mechanism is discussed.

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Section: Methodsmentioning

confidence: 91%

Stomatal Behaviour Following Treatment With Auxin‐like Substances and Phenylmercuric Acetate

Mansfield

1967

New Phytologist

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“…The ATP photochemically generated by cyclic photophosphorylation may be used not only for CO2 assimilation but also for other ATP-requiring cellular activities (11). One example of such "nonphotosynthetic" use of ATP derived from cyclic photophosphorylation is amino acid incorporation by isolated chloroplasts (46 is curtailed or stopped altogether because of the well-known midday closure of stomata in leaves (47,48). A curtailment of CO2 assimilation would result in an accumulation of NADPH; hence the possibility arose that NADPH might have an effect on the operation of cyclic photophosphorylation.…”

Section: Resultsmentioning

confidence: 99%

Regulation of ferredoxin-catalyzed photosynthetic phosphorylations.

Arnon¹,

Chain²

1975

Proc. Natl. Acad. Sci. U.S.A.

134

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Under aerobic conditions that are likely to prevail in chloroplasts in vivo, the optimal concentration of ferredoxin for cyclic photophosphorylation was found to be equal to that required for NADP reduction and about onetenth of that needed for cyclic photophosphorylation under anaerobic conditions. In the presence of ferredoxin and NADP, cyclic photophosphorylation operated concurrently with noncyclic photophosphorylation, producing an ATP: NADPH ratio of about 1.5. The effective operation of ferredoxin-catalyzed cyclic photophosphorylation by itself required a curtailment of the electron flow from water which was accomplished experimentally by the use of either an inhibitor or far-red monochromatic light. An unexpected discovery was that the operation of cyclic photophosphorylation by itself was also regulated by a back reaction of NADPH and ferredoxin with two components of chloroplast membranes, component C550 and cytochrome b559. The significance of these findings to photosynthesis in vivo is discussed.Solar energy is first converted into biologically useful chemical energy by photosynthetic phosphorylation (photophosphorylation), the process by which the photosynthetic apparatus transforms the electromagnetic energy of sunlight into phosphate bond energy of ATP, the universal energy carrier of living cells. The energy of the photochemically generated ATP and reducing power is conserved through the biosynthesis of organic compounds from CO2. When these are later degraded by fermentation and respiration, reducing power and ATP are regenerated to drive the multitude of endergonic reactions and activities of living cells.Chloroplasts, the photosynthetic organelles of green plants, have two types of photophosphorylation, cyclic and noncyclic, names devised to denote the coupling of ATP formation to a light-induced electron flow that is either of a closed (cyclic) type that yields only ATP or of a unidirectional (noncyclic) type that yields not only ATP but also NADPH as reducing power (1). Ferredoxin plays a key role in both. In cyclic photophosphorylation ferredoxin is the endogenous catalyst (2, 3) and in noncyclic photophosphorylation ferredoxin is the electron acceptor (4) that in turn reduces NADP by an enzymatic reaction that is independent of light (5).In this paper we report the concurrent operation of ferredoxin-dependent cyclic and noncyclic photophosphorylation under conditions that are likely to exist in chloroplasts in vivo. These experiments led to the discovery that noncyclic electron flow provides a regulatory mechanism that permits cyclic photophosphorylation to operate either concurrently with the noncyclic type (and thereby to increase the ratio of ATP to NADPH as needed for photosynthetic CO2 assimilation) or to operate by itself and produce only ATP for those endergonic reactions that do not require photochemically generated reducing power. Illumination. Incident monochromatic illumination was provided by a 250 W tungsten-halogen lamp (General Electric type EHN) and appropriate inte...

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“…The water deficit is a very powerful regulator. When the defi cit rises above the critical value, it overrides all opening stimuli and causes closing even in high intensity light (81) or in CO2-free air (82). The water deficit is the only regulator of the aperture of the hydathodes in the wheat coleoptile (83).…”

Section: Environmental Factors Controlling Stomatal Movementmentioning

confidence: 99%

Stomatal Physiology

Ketellapper¹

1963

Annu. Rev. Plant. Physiol.

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The Stomata as a Hydrophotic Regulator of the Water Deficit of the Plant

Cited by 119 publications

References 20 publications

Stomatal Behaviour Following Treatment With Auxin‐like Substances and Phenylmercuric Acetate

Stomatal Behaviour Following Treatment With Auxin‐like Substances and Phenylmercuric Acetate

Regulation of ferredoxin-catalyzed photosynthetic phosphorylations.

Stomatal Physiology

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