The Absorption of Ions by Microorganisms and Excised Roots

Barber, D. A.

doi:10.1111/j.1469-8137.1974.tb04609.x

Cited by 12 publications

(3 citation statements)

References 24 publications

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“…Since the characteristic distribution of thallium and silver occurs under conditions of considerable toxicity, it seems unlikely that an active shuttle between subsidiary and guard cells is involved (cf. Barber, 1974). There is also a phase shift between the kinetics of stomatal opening and those of ion accumulation in the guard cells (Laffray, Louguet & Garrec, 1982).…”

Section: Ion Accumulation Within the Epidermismentioning

confidence: 99%

The role of peristomatal transpiration in the mechanism of stomatal movement

Maier-Maercker¹

1983

Plant Cell & Environment

110

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Abstract. Peristomatal transpiration is defined as the relative high local rate of cuticular water loss from external and internal surfaces around the stomatal pore and its decisive role in the control of stomatal movement is re‐emphasized. As the resistance towards changes in air humidity is low in the pore surroundings, the state of turgor is particularly unsteady there. Due to the inherent instability the guard cell ‘senses’ fluctuations in the supply‐demand relationship of water and is thus the control unit proper. The environmental variables (supply and demand) are cross‐correlated within the subsidiary cell and the information is transmitted to the guard cell through the water potential gradient between the two cells. A conceptual segregation of a ‘humidity response’ by ‘passive’ stomatal movements is rejected. As ions always accumulate at the most distant point of the liquid path and as this point varies with pore width according to the prevailing water potential gradients, it is felt that the water stream is causing the characteristic pattern of ion distribution within the epidermis. Passive import of ions is attributed to local concentration gradients which are steepened by continuous supply and by water uptake into the guard cell in response to starch hydrolysis. A mechanistic model supplements the discussion.

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Section: Ion Accumulation Within the Epidermismentioning

confidence: 99%

The role of peristomatal transpiration in the mechanism of stomatal movement

Maier-Maercker¹

1983

Plant Cell & Environment

110

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“…Similarly, Tl"^ which is an excellent biological substitute for K"^ in in vitro and in a few in vivo studies (Williams, 1970;Lee, 1972;Chock and Titus, 1973) is present predominantly in a non-exchangeable form in Umbiliearia muhlenbergii and would therefore also appear to be located within the cell (Nieboer et al, 1976b). (Tr is readily absorbed into the protoplasm of higher plants (Lee, 1972) and is very toxic (Lee, 1972;Barber, 1974). )…”

Section: Potassium Efflux As a Function Of [So2]mentioning

confidence: 99%

Potassium Efflux by Lichen Thalli Following Exposure to Aqueous Sulphur Dioxide*

et al. 1977

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Summary Potassium efflux is a useful experimental quantity for assessing damage to lichens exposed to SO2. This SO2‐induced K+ efflux is biphasic in response to increasing concentrations of aqueous SO2. The first phase can be extrapolated to identify the SO2 concentration at which no K+ release occurred above the control values. This threshold concentration was used to determine the relative sensitivities of various lichen species. Good agreement was observed between the total K+ lost and the reduction in the total photosynthetic 14C‐fixation rates. The magnitude of the SO2‐induced K+ efflux indicated that release occurred from intra‐cellular sources. The kinetics of the release process and the effects of SO2 on membrane integrity are discussed.

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“…Some authors have proposed the existence of two transport systems (7), or a transport system plus a diffusion component (11), operating in parallel in the plasmalemma or in series in the plasmalemma and tonoplast (12). For some others, the kinetics of a system which intrinsically obeys Michaelis-Menten kinetics is modified by external factors, such as the presence of microorganisms in the roots (2) or the unstirred layers outside the membrane (4). Finally, for others the cause of the complex kinetics is intrinsic to the transport protein(s), which either experience conformational changes at different substrate concentrations (14) or changes in transport activity due to a sequential binding of K+ (22).…”

mentioning

confidence: 99%

Two Modes of Rubidium Uptake in Sunflower Plants

Benlloch¹,

Moreno²,

Rodríguez‐Navarro³

1989

Plant Physiol.

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The Rb+-uptake kinetics in K+-starved sunflower (Helianthus annuus) plants can be explained by the addition of two MichaelisMenten equations. In contrast, Rb+ uptake can be described by a single Michaelis-Menten equation in normal-K plants. Differences in the Kms and in the Arrhenius plots of Rb+ uptake in the two types of plants suggest two uptake modes.(16 and unpublished data of these authors). This system is a 180 kD protein with 12 potential membrane-spanning domains (8).Considering the similarities between plants and fungi in some of the basic transport processes (24), and the similarities between N. crassa and plants in the kinetics of Rb+ uptake, some experiments were designed to disclose more extensive similarities between K+ and Rb+ uptake in plants and fungi.K+ uptake in plants does not exhibit simple MichaelisMenten kinetics. Instead, complex K+ uptake kinetics are usually observed, which have been explained by many different hypotheses. Some authors have proposed the existence of two transport systems (7), or a transport system plus a diffusion component (11), operating in parallel in the plasmalemma or in series in the plasmalemma and tonoplast (12). For some others, the kinetics of a system which intrinsically obeys Michaelis-Menten kinetics is modified by external factors, such as the presence of microorganisms in the roots (2) or the unstirred layers outside the membrane (4). Finally, for others the cause of the complex kinetics is intrinsic to the transport protein(s), which either experience conformational changes at different substrate concentrations (14) or changes in transport activity due to a sequential binding of K+ (22).The negative effect of the K+ content on K+ uptake (9, 10), another observable characteristic of these kinetics, has been explained by an allosteric regulation of the system operating at the lower range of K+ concentrations (9, 15) or by longdistance regulation (6).In Helianthus annuus seeds (cv Sun-Gro 380 Eruosemillas, S.A. C6rdoba, Spain) were surface-sterilized in 0.5% NaOCl (1 min) and germinated in perlite irrigated with 5 mM CaCl2. Five-day-old seedlings were transferred to a K+ free nutrient solution complemented with the amount of KC1 required in each experiment and were grown for an additional 9-d period, unless otherwise stated. The K+-free nutrient solution was a slight modification of one previously described (5): 2.5 mm Ca(NO3)2, 1.0 mM MgSO4, 0.25 mM Ca(H2PO4)2, 12.5 ,uM H3BO3, 1.0 AM MnSO4, 1.0 AM ZnSO4, 0.25 MM CuSO4, 0.2 Mm (NH4)6Mo7024, and 10 AM Fe-ethylenediamine-di-o-hydrosyphenylacetic acid. Ca(OH)2 was used to adjust the pH to 5.5. Plants were grown under constant aeration of the nutrient solution in a chamber at 22°C day/l 8°C night, with a 13-h photoperiod and a photosynthetic photon flux density of 350 Mmol m-2s-' at the height of the plant canopy (fluorescent tubes, Sylvania cool white VHO).

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The Absorption of Ions by Microorganisms and Excised Roots

Cited by 12 publications

References 24 publications

The role of peristomatal transpiration in the mechanism of stomatal movement

The role of peristomatal transpiration in the mechanism of stomatal movement

Potassium Efflux by Lichen Thalli Following Exposure to Aqueous Sulphur Dioxide*

Two Modes of Rubidium Uptake in Sunflower Plants

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