A Comparison of the Uptake and Translocation of some Organic Molecules and Ions in Higher Plants

Shone, M. G. T.; Clarkson, David T.; Sanderson, John P.; Wood, Ann V.

doi:10.1016/b978-0-12-058250-1.50058-0

Cited by 17 publications

(14 citation statements)

References 31 publications

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“…It is well known that calcium and hydrogen ions play an important role in the control of ionic transport across the cytoplasmic membranes of plant cells (Shone et al, 1973;Clarkson, 1974;Luttge & Higinbotham, 1979). One of the possible mechanisms of this control is the interaction of these cations with fixed membrane surface charges.…”

Section: Ca 2+ and H + Effect On Plasmalemma Surface Chargesmentioning

confidence: 98%

Potassium channels in plasmalemma ofNitella cells at rest

Соколик¹,

Yurin²

1986

J. Membrain Biol.

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Summary. Cation channels of passive transport in the plasmalemma of Nitella flexilis cells at rest were studied by the voltageclamp technique using microelectrodes. Two types of potassium channels have been identified. They are activated at different voltages: over -100 to -80 mV (D-channels) and below -100 mV (H-channels). The zero-current potential of instantaneous voltage-current curves (IVCC's) for both types of channels shifts by 50 to 55 mV in response to a 10-fold increase of K + concentration in the solution. Ion movement in D-channels follows the free diffusion mechanism; in H-channels the independence principle is violated. The channel selectivity (in the order of decreasing permeability) is: K + > Rb + > NH~ > Na + > Li + > Cs + > TEA + choline*. It has been found that D-channel Cs + block is potential dependent while tetraethylammonium (TEA +) blocks Hchannels in a potential-independent manner, but H + ions do not affect the inward potassium current of the channels. Two types of potassium channels appear to be located in different parts of the membrane and their entrance parts are of different structure.

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Section: Ca 2+ and H + Effect On Plasmalemma Surface Chargesmentioning

confidence: 98%

Potassium channels in plasmalemma ofNitella cells at rest

Соколик¹,

Yurin²

1986

J. Membrain Biol.

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“…If J* is the membrane water flux then V = J* (7rr2 + 2nTrl) and v. = J* (77r2 + 2 7rrs) from which vs=V( 2s )r (2) dv,_ V ds-T (3) also in the source leaf C0 is constant and nonzero by hypothesis for 0 G s -1*. Substituting equations 2 and 3 into 1 we get (9) Co.9L/C°i s plotted against P* (Fig. 4), i.e.…”

Section: Theorymentioning

confidence: 99%

“…It has been assumed that the potential for a chemical to penetrate the plasmalemma of the cells is correlated with the over-all pattern of translocation it achieves in the plant as a whole. It was originally thought that chemicals displaying an apoplastic transport pattern were unable to penetrate the plasmalemma of plant cells and thus were excluded from the plant symplasm but recent investigations have shown that several chemicals termed apoplastic do penetrate plant cell membranes (4,(7)(8)(9)(10)13). Peterson and Edgington (7) have called such chemicals pseudoapoplastic.…”

mentioning

confidence: 99%

A Simple Theory Regarding Ambimobility of Xenobiotics with Special Reference to the Nematicide, Oxamyl

1979

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A theory is presented to explain the phloem mobility of certain systemic xenobiotics that are not weak acids. It is shown that there is a theoretically optimum permeability that permits optimum circulation through the symplasm and apoplast (including the phloem and xylem) of Solanum tuberosum plants. The optimum permeability is large enough to permit substantial passive permeation into sieve cells in the source leaf and yet is small enough to permit phloem ransport with some retention. The optimum permeability is a function of the velocity of sap flow in sieve tubes, the radius of the sieve tube, the over-all length of the plant, and the length of the carbohydrate and xenobiotic sources. It is argued that the nematicide, oxamyL is near the optimum permeability under some experimental conditions. It is shown that depending on the strength of the carbohydrate sink in roots or growth points and depending on the permeability of the xenobiotic, there can be passive accumulation of xenobiotics in the sieve tubes in the carbohydrate sink regions.The patterns of translocation which various xenobiotic substances display after entering a plant have been described for many chemicals, especially herbicides (1). Two distinctive patterns of transport were discerned, namely the apoplastic pattern and the symplasmic pattern. Movement in the apoplast occurs mainly via the xylem and the cell walls of the parenchyma cells, while movement in the symplasm occurs via the phloem and the interconnected protoplasts of the parenchyma cells. Chemicals moving by both routes are called ambimobile (5). It has been assumed that the potential for a chemical to penetrate the plasmalemma of the cells is correlated with the over-all pattern of translocation it achieves in the plant as a whole. It was originally thought that chemicals displaying an apoplastic transport pattern were unable to penetrate the plasmalemma of plant cells and thus were excluded from the plant symplasm but recent investigations have shown that several chemicals termed apoplastic do penetrate plant cell membranes (4, 7-10, 13). Peterson and Edgington (7) have called such chemicals pseudoapoplastic. They suggested that the permeability of the plasmalemma to the pseudoapoplastic chemical is so great that it cannot be retained in the symplasm for long

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“…own nature of uptake is still in doubt. The low order of accumulation of Ca by root tissues observed in conventional excised root experiments has been ascribed to a low permeability of the plasmalemma to Ca (Moore et al 1961, Shone et al 1973). but other explanations are possible.…”

Section: Discussionmentioning

confidence: 99%

“…Robards el al. 1973, it has been hypothesized that Ca may be unable to enter vascular tissues in mature zones of roots due to the suberization of endodermal cell walls (Shone et al 1973). Since intact plants of most species are known lo take up substantial amounts of Ca, these observations appear to support the concept of Ca uptake and transport by bulk flow of solution (MooTt et al 1961, Barber andKoontz 1963).…”

Section: Introductionmentioning

confidence: 96%

The Accumulation and Transport of Calcium in Barley Roots

Singh

Jacobson

1979

Physiologia Plantarum

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The accumulation and transport of Ca by various zones of 6‐day old barley roots (Hordeum vulgare L.) were examined with special reference to their relationship to the salt status of the root. The initial salt content had a profound effect on Ca transport and a lesser effect on Ca accumulation. High‐salt roots transported Ca in much larger amounts than did low salt roots. In low salt roots the apical zone was more active in transporting Ca to the conducting tissue than were the mid or basal zones However, in high salt roots all zones were about equally active in transporting Ca. The metabolic inhibitor, DNP, had little effect on accumulation but inhibited transport very effectively. The effect of DNP was more pronounced on transport from the apical zone than from the other root zones. Calcium applied anywhere along the root length moved only basally and its polarized longitudinal movement was maintained irrespective of the salt status of the root. The movement of Ca was characterized by a rapid release of preabsorbed Ca and a ready exchange of apoplastic Ca. The hypothesis is presented that cellular Ca is in a relatively mobile state. Its entry into the symplasm is the rate limiting step in longitudinal transport and its overall movement is metabolically controlled.

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A Comparison of the Uptake and Translocation of some Organic Molecules and Ions in Higher Plants

Cited by 17 publications

References 31 publications

Potassium channels in plasmalemma ofNitella cells at rest

Potassium channels in plasmalemma ofNitella cells at rest

A Simple Theory Regarding Ambimobility of Xenobiotics with Special Reference to the Nematicide, Oxamyl

The Accumulation and Transport of Calcium in Barley Roots

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