Redistribution of Potassium, Calcium, Magnesium, and Manganese in the Plant

The extent of redistribution in apple was described by calculating the fruit/leaf ratio of the cation content. It was found that the redistribution diminishes in the sequence K > Mg > Ca ～ Mn. These results are more or less in agreement with those found elsewhere. Investigations were made to see whether it was possible to account for the differences in redistribution by the phloem by means of the solubility of these cations in the sieve tube sap. As model plants Yucca flaccida and Ricinus communis were used, plants from which it was possible to obtain phloem sap in a rather pure state. It was found that the addition of potassium and magnesium as a chloride in the usual investigated range of concentrations did not give precipitation. With calcium and manganese, however, a precipitate soon occurred. Manganese was demonstrated to be less soluble than calcium. For Ricinus the maximum amount of calcium and manganese the sieve tube sap could contain before precipitation set in was higher than for Yucca sap. The results confirm the possibility that the redistribution of the different cations in the plant can be related inter alia to their solubility in the sieve tube sap. It was also found that the calcium in the phloem sap is present in ionic condition. Thus the normal laws of solubility should be applicable.     

Effect of Potassium, and Abscisic and Indole-3-Acetic Acids, on Maize Root Xylem Exudation and Potassium Efflux

The influence of potassium sulfate, abscisic acid (ABA) and indole-3-acetic acid (IAA) solutions on xylem exudation rate and potassium efflux from the apical cut end of root tips of intact maize (Zea mays L. cv. Dnepropetrovskaya) seedlings was studied. Foliar application of 5 mM K₂SO₄ considerably stimulated the exudation rate. The application of ABA and IAA (1 mM) also induced a high rate of xylem exudation, K⁺ efflux being simultaneously increased. This revised version was published online in July 2006 with corrections to the Cover Date.     

Muscle Potassium and Potassium Losses During Hypokinesia in Healthy Subjects

Hypokinesia (HK) induces electrolyte losses in electrolyte-deficient tissue, yet the mechanisms of electrolyte losses in electrolyte-deficient tissue remain unknown. Mechanisms of electrolyte deposition could be involved. To determine the effect of prolonged HK on potassium (K⁺) deposition were measured muscle K⁺ content and K⁺ losses. Studies were conducted on 20 physically healthy male volunteers during 30 days pre-experimental period and 364 days experimental period. Subjects were equally divided into two groups: control subjects (CS) and experimental subjects (ES). The CS group was run average distances of 9.8 ± 1.7 km day⁻¹ and the ES group was walked average distances of 2.7 ± 0.6 km day⁻¹. Muscle K⁺ content decreased (p < 0.05) and plasma K⁺ concentration, and K⁺ losses in urine and feces increased (p < 0.05) in the ES group compared to their pre-experimental level and the values in their respective CS group. Muscle K⁺ content, plasma K⁺ level, and urine and fecal K⁺ losses did not show any changes in the CS group compared to their pre-experimental values. The conclusion was that K⁺ losses in K⁺-deficient muscle of healthy subjects could have been attributable to the less efficient K⁺ deposition inherently to prolonged HK.     

Potassium, neuroglia, and oxidative metabolism in central gray matter.

Reviewed is the author's investigation of potassium in extracellular fluid of cerebral neocortex and spinal cord determined with ion-selective microelectrodes, and of oxidative metabolism monitored by fluorometric determination of intramitochondrial NADH in intact cortex. When gray matter is excited by afferent input, or by direct electrical stimulation, the logarithm of the rise of extracellular potassium concentration ([K+]0), the sustained shift of electrical potential, and the response of oxidative metabolism are linearly correlated. However, during seizures and during spreading depression, the correlation is broken, suggesting that the demand for oxidative energy exceeds that corresponding to the elevation of [K+]0. There exists a critical concentration of [K+]0 at which spreading depression inevitably erupts (12 mM for cat cerveau isole), but no such critical level could be detected for seizures. The rate of clearance of excess potassium from extracellular fluid is slower for high concentrations than for low; this rate is further slowed by the administration of phenobarbital, and possibly also of diphenylhydantoin. Changes of membrane potential of glia cells in the mammalian spinal cord can adequately be described by the Nernst equation.     

Potassium, sodium and Chloride in the protoplasm of characeae

Using vacuolar perfusion, which enabled us to replace the cellsap with a solution containing no k⁺, Na⁺ and Cl^–, theconcentrations of these ions in the protoplasm of three speciesof fresh water Characeae were determined. They were respectively,78, 2 and 27 mM in Nitella flexilis, 101, 9 and 31 mM in Nitellapulchella, and 112, 3 and 21 mM in Chara australis. Our previouslyreported results (3) indicating that the chloroplast layer containedmuch more Na⁺ and Cl^– than the endoplasm has been questionedin the light of the present results. ¹Present address: Department of Biology, College of GeneralEducation, Osaka University. (Received September 5, 1973; )     

多种农药与次氯酸钠、高锰酸钾和高铁酸钾的反应活性

为探究4类,10种广泛使用的农药(苯氧羧酸类,芳香酸类,取代脲类和烟碱类)与3种氧化剂(次氯酸钠,高锰酸钾和高铁酸钾)的反应活性,本研究在温度(25±2)℃、pH值为8的条件下,分析10种农药分别与3种氧化剂NaClO、KMnO4、K2Fe O4在不同浓度下的反应活性,采用HPLC检测法,对比降解效能,探究氧化剂性质与有机物结构导致的反应活性的差异。实验结果表明,不同种类农药的结构性质对反应活性有重要影响,3种氧化剂的氧化降解能力有明显差异。苯氧羧酸类和芳香酸类农药结构较简单,并含有稳定的苯环或吡啶环结构,氧化降解较困难。取代脲类和烟碱类农药结构较复杂,氧化剂可攻击其不饱和官能团,反应活性较高。NaClO对取代脲类农药的降解率明显优于其他2种氧化剂,3种氧化剂对烟碱类农药的氧化降解效果依次为NaClO>KMn O4>K2Fe O4。研究多种农药与次氯酸钠、高锰酸钾和高铁酸钾的反应活性对降解去除水体中的农药残留对水环境的治理具有重要意义。     

Cerebrovascular Permeability Coefficients to Sodium, Potassium, and Chloride

CSF and regional brain concentrations of 42K, 22Na, 36Cl, and [14C]mannitol were determined 3-45 min after intravenous injection of the tracers in pentobarbital-anesthetized rats. Rapid influx of 36Cl and 22Na into ventricular CSF immediately established concentration gradients from CSF to brain extracellular fluid. The CSF contribution to brain uptake of tracers was greatest in periventricular brain regions, where brain 36Cl concentrations were up to ninefold higher than concentrations in regions distant from ventricular CSF. Acetazolamide (20 mg kg-1 i.p.), an inhibitor of CSF formation, decreased 36Cl uptake into CSF and into periventricular brain regions but not into frontal cortex. 36Cl uptake into brain was unidirectional for 10 min after intravenous injection, and, during that period, diffusion from ventricular CSF did not contribute to uptake in the frontal cortex. Therefore, cerebrovascular permeability coefficients could be calculated from tracer concentrations in frontal cortex at 10 min and equaled, in cm s-1, 13.5 X 10(-7) for 42K, 1.4 X 10(-7) for 22Na, 0.9 X 10(-7) for 36Cl, and 1.5 X 10(-7) for [14C]mannitol. The low cerebrovascular permeabilities to K, Na, and Cl, comparable to those of some cell membranes, and the permselectivity (K much greater than Na greater than Cl) suggest that a significant fraction of ion transport across cerebral capillaries is transcellular, i.e., across the endothelial cell membrane.     

Insulin,Glucose, and Potassium in the Treatment of Congestive Heart Failure

A daily infusion of 500-1,000 ml of 50% glucose containing 100-120 units of soluble insulin and 100-120 mEq of potassium chloride per litre was given to six patients suffering from hyponatraemia and congestive cardiac failure resistant to digoxin and diuretic therapy. In two patients there was no response, but four showed a striking improvement with a sodium and water diuresis, a rise in plasma sodium level, and in two cases a reversion from atrial fibrillation to sinus rhythm. It is suggested that insulin, glucose, and potassium given by the intravenous route in adequate dosage forms a useful adjunct to the management of severe congestive heart failure.     

Effects of Vapor Pressure Deficit and Potassium Supply on Root Morphology,Potassium Uptake,and Biomass Allocation of Tomato Seedlings

Journal of Plant Growth Regulation - Atmospheric humidity, defined as the vapor pressure deficit (VPD), is an important factor affecting plant transpiration and nutritional status. Previous work...     

Potassium,calcium and magnesium antagonism in clones of Populus trichocarpa

Two clones of Populus trichocarpa varying in growth rate were grown in nutrient solutions with a range of K supply. In the leaves an antagonism between the levels of K and Ca+Mg was found, this was most extreme in the older leaves. Analysis of the contents of these elements in leaf vacuoles and cytoplasm suggests that in the vacuoles the total contents of K+Ca+Mg are controlled to maintain ionic and osmotic balance. At low K supply, the K deficit in the cytoplasm is not balance by accumulation of Ca and Mg, and it is suggested that other organic osmotica may accumulate. The regulation of K+Mg+Ca supplied to the leaves seems to be regulated by the roots and is not simple competition of ions for uptake sites at the plasmalemma.     

Potassium transporters in plants--involvement in K+ acquisition, redistribution and homeostasis

Potassium is a major plant nutrient which has to be accumulated in great quantity by roots and distributed throughout the plant and within plant cells. Membrane transport of potassium can be mediated by potassium channels and secondary potassium transporters. Plant potassium transporters are present in three families of membrane proteins: the K(+) uptake permeases (KT/HAK/KUP), the K(+) transporter (Trk/HKT) family and the cation proton antiporters (CPA). This review will discuss the contribution of members of each family to potassium acquisition, redistribution and homeostasis.     

Potassium transport by rabbit descending colon, in vitro

Studies of the bidirectional fluxes of K across segments of rabbit descending colon indicate that: a) when the tissue is short-circuited, the net flux does not differ significantly from zero under control conditions and in the presence of aldosterone; and b) the bidirectional fluxes of K conform to the Ussing flux-ratio equation over a wide range of transepithelial electrochemical potential differences. These and other findings strongly suggest that the movements of K across the epithelium are restricted to paracellular routes and are entirely passive. Studies dealing with the mechanism of homocellular K transport indicate that: a) K is actively transported into the cells across the basolateral membranes against an electrochemical potential difference of approximately 30 mV; and b) the active uptake of K may be mediated by a rheogenic Na-K exchange pump that is also responsible for transcellular Na transport. These results are entirely consistent with the model proposed by Koefoed-Johnson and Ussing for isolated frog skin.