Studies on the Absorption, Distribution and Release of Labelled Rubidium Ions in Young Intact Barley Plants

Helder, R. J.

doi:10.1111/j.1438-8677.1958.tb00619.x

Cited by 25 publications

(10 citation statements)

References 30 publications

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“…The lack of transport site saturation, coupled with the reduced vacuolar accumulation of Cl36 following short pretreatments, enabled more of the absorbed C136 to be transported to the xylem (fig 4). This situation is apparently analogous to other reports which show a greater rate of ion transport in high salt plants than in low salt plants (6,7,16,17,18 (fig 4).…”

Section: Discussionsupporting

confidence: 75%

“…Although similar data have been presented by other investigators, (5,15,16,18), some studies show that the transport of various ions to plant shoots or xylem exudates in high salt plants is greater than in low salt plants (6,7,16,17,18).The concentration of the external solution appears to play an important role in determining whether ion transport to shoots will be greater or smaller in high salt plants relative to low salt plants. Russell, Martin, and Bishop (18) and Russell and Shorrocks (16) have shown that high salt barley plants transport p32 (salt not specified) to shoots at a greater rate than do low salt plants when the external concentration is low, but that the reverse is true when the external concentration is high.…”

supporting

confidence: 51%

supporting

confidence: 50%

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Chloride Uptake and Transport of Different Salt Status

Hodges¹,

Vaadia²

1964

Plant Physiol.

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In a previous report (8) it was shown that the rate of radiochloride transport to the exudation stream of single exuding roots was less in high salt roots than in low salt roots. Although similar data have been presented by other investigators, (5,15,16,18), some studies show that the transport of various ions to plant shoots or xylem exudates in high salt plants is greater than in low salt plants (6,7,16,17,18).The concentration of the external solution appears to play an important role in determining whether ion transport to shoots will be greater or smaller in high salt plants relative to low salt plants. Russell, Martin, and Bishop (18) and Russell and Shorrocks (16) have shown that high salt barley plants transport p32 (salt not specified) to shoots at a greater rate than do low salt plants when the external concentration is low, but that the reverse is true when the external concentration is high. Furthermore, Russell and Shorrocks showed that a relationship exists between nutrient transport to shoots and transpiration rates only when high salt plants or high external concentrations are used. Similar data were presented earlier by Broyer and Hoagland (3). Hylmb and colleagues (9, 10, 11) have interpreted this type of relationship to mean that ions are passively swept into and across the root to the xylem with the transpiration stream. Broyer and Hoagland and Russell and Shorrocks, however, feel that the more rapid removal of ions from the vascular tissue caused by enhanced transpiration, serves to increase the overall rate of active ion transfer.Since the possibility exists that the salt status of the xylem stream may affect the rate of ion entry into the xylem, this particular point has been investigated and the results are presented here. In addition, the effect of the chloride content of the root tissue on the rate of Cl36 transport to the exudation stream of individual roots was investigated. Materials and MethodsIndividual exuding onion (Alliurn cepa, var. Early Grano) roots were used for all experiments.

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Section: Discussionsupporting

confidence: 75%

supporting

confidence: 51%

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Chloride Uptake and Transport of Different Salt Status

Hodges¹,

Vaadia²

1964

Plant Physiol.

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“…This site has a much higher affinity for K than for Na when Ca is present, hence the sharp drop in Na absorption at even low K concentrations, in the presence of Ca (figs 7,8).…”

Section: Discussionmentioning

confidence: 99%

The essential role of calcium in selective cation transport by plant cells

1961

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The mechanisms whereby plant cells absorb inorganic ions from the external media are selective: they discriminate among different ions. Particularly intriguing is the discrimination between potassium and sodium ions. Most plant cells accumulate much higher concentrations of potassium than of sodium ions, even from media in which the sodium concentration greatly exceeds that of potassium.Perhaps the best way to investigate these specificities is to study the manner in which different ions affect each other's absorption. In a previous paper (4) experiments were described demonstrating that in excised barley roots potassium and rubidium compete with each other in an identical absorption mechanism. At moderate concentrations, neither sodium nor lithium ions competed for the potassium-rubidium transport mechanism. The deduction was that there are specific ion binding sites on carrier molecules which effect the transport of the ions across cellular membranes. Potassium and rubidium ions are bound and transported by sites which fail to discriminate between them, hence these ions compete with each other for identical carrier sites. Sodium and lithium are not bound by the potassium-rubidium sites, hence do not compete with potassium and rubidium but are transported by separate sites.In this paper experiments with barley roots are presented which show that calcium ions are essential for the integrity of the selective absorption mechanism referred to, and information is given about some quantitative features of the calcium effect. MATERIALS & METHODSThe distilled water piped into the laboratory was passed through a mixed ion exchange column2 to free it from heavy metal and other impurities. This purified water was stored in pyrex carboys. Glassware was rinsed with about 0.5 M HCl, followed by exhaustive rinsing with distilled water. Salts used 'Received January 9, 1961. This assembly was placed in the dark, at room temperature. The solution was aerated continuously. Three days after the seeds were planted on the cheesecloth, the stainless steel screen with the seedlings was removed from the beaker, the roots were rinsed in two changes of water, and the assembly put on a beaker with fresh solution. The watchglass was not replaced. Two days after this, the roots were rinsed repeatedly in water, excised just below the screen, rinsed several more times, and suspended in about four liters of water.ABSORPTION EXPERIMENTS. For the experiments proper, roots were gently blotted on dry cheesecloth which had been washed and rinsed with distilled water. One-gram samples were weighed out on a torsion balance and transferred to 100 ml water in 30 X 300 mm culture tubes. The tubes were placed in a waterbath maintained at 30°C, and the water in the tubes was aerated. To start the absorption period proper, each tube in turn was removed from the bath, the water was decanted, the roots were rinsed twice with about 100 ml water each time, and 100 ml of prepared experimental solution were then poured in. The tubes were replaced in the bath, an...

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“…Helder (11) began to degrade. The lowered respiration was related to loss of mitochondrial activity.…”

Section: 'Lant Physiologymentioning

confidence: 99%