Der Einfluss der K-Konzentration der Nährlösung auf die Ertragsbildung,die Qualität und den K-Aufnahmeverlauf bei Hafer

Summary 1. In solution culture with oats (Avena sativa) the effect of the K concentration of the nutrient solution on yield and K uptake rates has been investigated. The K concentration of the different treatments were: 0.1, 0.3, 0.9 and 2.7 me K/l. These concentrations were kept constant during the whole growing period. 2. The growth of the plants in all treatments was normal. Even with the lowest K concentration no visible symptoms of K deficiency occurred. The highest grain yield was obtained with a K concentration of 0.9 me K/l. This yield was about 40% higher than the yield with the lowest K concentration and about 5% higher than the grain yield with the highest K concentration. 3. The increasing K supply had a favorable effect on the fat and crude protein content of the grains. The highest K concentration (2.7 me K/l) resulted in the highest content of crude protein (20%) and of fat (6.2%). 4. The rates of K uptake throughout the growing period differed considerably. The highest rates were measured during the shooting stage and the blossom stage. The K concentration of the nutrient solution influenced the uptake rates significantly. High yields were obtained if the K uptake at the beginning of the blossom stage was higher than 50% of the total K uptake. 5. The optimal K concentration for the yield performance, 0.9 me K/l, found in this experiment cannot be compared with K concentrations of the soil solution under field conditions without reservations. Under field conditions root growth and the contact surface between soil solution and root surface are different. Assuming that under field condition this contact surface nutrient solution/root surface is not larger than in solution culture, also a K concentration of 1 me K/l of the soil solution should meet the K demand of the plants, necessary for the production of high grain yields.      

On catecholamine-containing cells in the rat interatrial septum

Summary The interatrial septum of the rat heart contains cells which show a strong intensive-yellow paraformaldehyde-induced fluorescence. By electron microscopy these cells are characterized by an abundance of dense-core vesicles.Cholinergio axons form axo-somatic synaptic contacts with the catecholamine-containing cells. These cells, packed with dense-core vesicles, are frequently interdigitated and interconnected by zonulae and maculae adhaerentes and occludentes. The catecholamine-containing cells are surrounded by satellite cells either individually or in groups.The catecholamine-containing cells, which bear blunt, plumpish processes, can be subdivided, on the basis of position and morphology into two types. One class of cells lies within the fibroblast capsule of the intra-atrial ganglion (van der Zypen, Hasselhorst, Merz and Fillinger, 1974). A second aggregation of catecholamine-containing cells occurs outside the ganglia in close proximity to capillaries. The capillaries exhibit pores in the area of contact with the catecholaminergic cells. The structure of these catecholamine-containing cells is described and their possible function discussed.

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Zusammenfassung Im Septum interatriale des Rattenherzens treten Zellen in Erscheinung, die nach Paraformaldehyd-Bedampfung eine intensive hellgelbliche Fluoreszenz zeigen. Diese Zellen zeichnen sich durch einen großen Reichtum an dense-core vesicles aus. Cholinerge Axone bilden axo-somatische Synapsen an den katecholaminhaltigen Zellen aus. Die mit dense-core vesicles angefüllten Zellen sind oft ineinander verzahnt und durch Zonulae adhaerentes verbunden. Einzeln oder in Gruppen werden die katecholamin-enthaltenden Zellen von Satelliten-Zellen umgeben.Die mit kurzen plumpen Fortsätzen versehenen katecholaminhaltigen Zellen lassen aufgrund ihrer Lage und eines andersartigen Baues zwei Typen erkennen. Eine Gruppe von Zellen liegt innerhalb der Fibrozytenkapsel des Ganglion intraatriale (van der Zypen, Hasselhorst, Merz und Fillinger, 1974). Eine zweite Ansammlung von Katecholamin enthaltenden Zellen findet sich außerhalb der Ganglien in engem Kontakt zu Kapillaren. Die Kapillaren weisen im Bereich des Kontaktes mit den katecholaminergen Zellen Poren auf. Die Struktur dieser Zellen wird geschildert und ihre mögliche Funktion diskutiert.

     

Turnover of organic nitrogen in soils and its availability to crops

The root development of barley seedlings grown for one week in an aerated nutrient solution was studied in the presence of dissolved organic matter from an aqueous chestnut leaf litter extract. In particular, the different effects of low and high molecular weight fractions (small molecules: molecular weight <1000; large molecules: >10,000) of the leaf litter extract were examined. In the presence of large molecules root growth was inhibited, an irregular root tip morphology was observed, and Ca and Mg concentrations in the shoots were lower than in control plants. These phytotoxic effects were not caused by the formation of an impermeable layer of large molecules on the root surfaces that lower accessibility for nutrient cations as inferred from voltammetric experiments. A germination assay using spruce seeds, however, indicated allelochemical effects of large molecules, which exhibit a higher aromaticity than the small molecules as indicated by spectroscopic characterisation. In the growth experiments with small molecules, no influence on the root development of barley was evident, but an increase of Ca and Mg in the shoots was detected. During these growth experiments, a large amount of the small molecules, mainly simple phenols and amino acids, disappeared from the nutrient solution. The loss of small molecules was most likely the effect of mineralisation.Abbreviations DOC dissolved organic carbon - DOM dissolved organic matter - LLE leaf litter extract - MW molecular weight - HMDE hanging mercury drop electrode     

Effect of potassium on the water potential, the pressure potential, the osmotic potential and cell elongation in leaves of Phaseolus vulgaris

The effect of potassium on the water potential, the osmotic potential and the pressure potential in younger and older leaves of Phaseolus vulgaris grown in hydroponic culture was studied. Inadequate potassium supply resulted in an increase of the osmotic potential. In the older leaves the water potential was raised, in the younger leaves the pressure potential was depressed in the treatment insufficiently supplied with potassium as compared with leaves with an adequate potassium supply. Cell size of the younger leaves was smaller in the treatment with the low K⁺ supply in comparison with the leaves well supplied with K⁺. Potassium had a beneficial effect on plant growth, especially on fresh matter production. The water status of leaves (water content, pressure potential, osmotic potential) responded more sensitively to potassium supply than dry matter production. Besides organic N and organic anions, K⁺ was the most abundant solute found in the press sap of the leaves. From the results it is concluded that K⁺ is indispensible for attaining an optimum potential (turgor) in young leaves which in turn has an impact on plant growth.     

Effect of Potassium Supply on the Rate of Phloem Sap Exudation and the Composition of Phloem Sap of Ricinus communis

The composition of phloem sap has been investigated in Ricinus communis var. gibsonii, grown for 2 weeks on nutrient solution of low and high potassium content (K(1) and K(2)). Diagonal cuts were made in the bark of the stem resulting in the exudation of clear droplets which mainly consisted of phloem sap. Although the plants at low K (0.4 mm) and high K (1 mm) did not differ in growth, leaf area, height, or stem circumference, the rate of exudation of the high K plants was about twice as high as that of the plants with the lower K supply. This promoting effect of K on exudation did not result in a dilution of organic (sucrose, UDP-glucose, ATP, UTP) and inorganic constituents of the phloem sap. For the following compounds, even significantly higher concentrations in the exudate were observed in the K(2) plants: potassium, raffinose, glucose 6-phosphate, and fructose 6-phosphate. Also, the osmotic pressure of the phloem sap was substantially increased in the higher K treatment. Experiments in which labeled (14)CO(2) was applied to one leaf showed that K had a favorable effect on the assimilation of CO(2), and in particular promoted the export of photosynthates from the leaf. It is suggested that the higher rate of phloem-loading in the plants with the better K supply is due to the higher CO(2) assimilation rate and especially to a better provision of ATP required for phloem loading. Higher phloem-loading rates result in higher osmotic pressure in the sieve tubes which probably gave rise to the higher flow rates observed in the plants with improved K supply.     

Measurements of pH in the apoplast of sunflower leaves by means of fluorescence

A method was elaborated by which the pH in leaf apoplast can be measured. The technique is based on the pH dependent fluorescence of 5-carboxyfluorescein (5-CF) or fluorescein isothiocyanate (FITC). The fluorescein isothiocyanate is coupled with a macromolecular dextran molecule (FITC-dextran). For eliminating the effect of the absolute dye concentration the dual excitation technique was applied. It was shown that the ratio of fluorescence excited by light of 491 nm and 463 nm was virtually independent of the concentration of 5-CF and that this fluorescence ratio was related to the pH. The plasmalemma is practically impermeable to FITC-dextran and in the test we carried out over a period of 6 h not the slightest indication was found that it may penetrate the plasma membrane. For 5-CF this cannot be ruled out completely. It is possible that at pH values below 4.5 it may penetrate biological membranes at low rates.
Experiments with leaves of sunflower ( Helianthus animus cv. Erika) perfused with 5-carboxyfluorescein and supplied with different nitrogen forms showed that NH⁺₄ application resulted in a decrease and NO⁺₃ application in an increase of the leaf apoplast pH. Leaf spraying with fasicoccin was followed by a pH decrease, while leaf spraying with the protonophores p -trifluoromethoxy carbonytcyanide phenylhydra-zon (FCCP) or nigericin resulted in neutral apoplastic pH. These results provide evidence that the method is well suited for measuring the response of the leaf apoplast pH to changing physiological conditions.     

Effect of potassium on uptake and incorporation of ammonium-nitrogen of rice plants

1. Rice was grown for 5 months in a sand solution culture at two different

1. K levels. The higher K supply resulted in a reduced uptake of Na +, Mg ++, and Ca++ by shoots. The uptake of NH4+-N of the shoots, however, was increased by the higher K supply.
2. In short term experiments, ill which the NH4+-N of the uptake solution was labelled by N 15, increasing K concentrations in the uptake solution did not depress the NH4 + uptake of young rice plants. Higher K concentrations in the uptake solution favoured the translocation of labelled N from the roots to the shoots. In some cases the higher K levels resulted also in an enhanced transfer rate of labelled N from the soluble to the insoluble N fraction.
3. Increasing levels of Mg++ in the uptake solution did not affect the uptake of labelled NH4-N.
4. I t is concluded that K + and NH4 + do not compete for common binding sites of the uptake mechanism in rice roots. This lacking competition suggests the speculation that NH4+-N is absorbed mainly in form of NH8 by plant cells.

     

Der Einfluss verschiedener Salze und verschiedener Inhibitoren auf den Wurzeldruck von Zea mays

The effect of different salts and inhibitors on the root pressure of Zea mays.— The influence of various salt solutions and inhibitors on the exudation rate has been investigated with young excised primary roots of Zea mays. The following results were obtained. — The effect of chlorides on the exudation rate was higher than the effect of sulphates K⁺ and Na⁺ effected higher flux rates than Ca²⁺ and Mg²⁺ The highest exudation rate was obtained with KCl. — In comparison to an isotonic Lutrol-solution (a liquid condensed polyethylenoxid) a 0.5525 molar KCl-solution, applicated on the root stump, increased the exudation rate considerably. — Metabolic inhibitors and anaerobic conditions decreased the exudation rate. — Experiments, concerning the influence of metabolic inhibitors on the exudation and on the Rb-uptake showed a highly significant positive correlation (r =+0.72***) between the exudation rates and the Rb-concentrations in the exudates. The Rb-accumulation in the root tissue was not correlated to the exudation rate. — The experimental data agree with the concept of a transversal water transport in the root tissue, effected by osmotic forces. The root pressure is based on the osmotic gradient between the xylem sap and the outer solution. This gradient is built up by the metabolic secretion of ions into the xylem sap. It is supposed that the transversal water transport in the roots mainly goes through the free space of the cortex.