Mobility of boron-polyol complexes in the hemiparasitic association between Rhinanthus minor and Hordeum vulgare: the effects of nitrogen nutrition.

Boron (B) is an essential nutrient required for plant growth and physiological processes. Long-distance B transport is facilitated by the formation of B-polyol complexes. We investigated B uptake and distribution in response to differing levels of exogenous nitrogen supply in the hemiparasitic association between Rhinanthus minor and Hordeum vulgare (barley) and in unparasitised barley and single Rhinanthus plants.

Does legume nitrogen fixation underpin host quality for the hemiparasitic plant Rhinanthus minor?

The high quality of leguminous hosts for the parasitic plant Rhinanthus minor (in terms of growth and fecundity), compared with forbs (non-leguminous dicots) has long been assumed to be a function of the legume's ability to fix atmospheric nitrogen (N) from the air and the potential for direct transfer of compatible amino compounds to the parasite. Using associations between Rhinanthus minor and Vicia faba (Fabaceae) that receive N either exclusively via symbiotic associations with rhizobia supplying organic N fixed from N(2) or exclusively through the supply of inorganic nitrate to the substrate, the underlying reasons for the quality of legumes as hosts for this parasite are unravelled. It is shown that sole dependence of the host, V.

Growth and development of the facultative root hemiparasite Rhinanthus minor after removal of its host.

Facultative plant hemiparasites exhibit optimal growth only when attached to a suitable host. After attachment, stomata of the parasite remain continuously open, thus, optimising the extraction of host xylem sap. When the host shoot was removed from the hemiparasitic Rhinanthus/barley association ~14 days after attachment, the resulting host-free attached Rhinanthus continued to grow and develop similarly well as the attached parasites.

Cytokinin flows from Hordeum vulgare to the hemiparasite Rhinanthus minor and the influence of infection on host and parasite cytokinins relations.

Using the facultative root hemiparasite Rhinanthus minor L. and Hordeum vulgare L. as a host, the flows, depositions and metabolism of zeatin-type cytokinins [zeatin (Z), zeatin riboside (ZR), zeatin nucleotide (ZN)] within the host, the parasite and between host and parasite have been studied during the period 41-54 d after planting (i.

Abscisic acid (ABA) flows from Hordeum vulgare to the hemiparasite Rhinanthus minor and the influence of infection on host and parasite abscisic acid relations.

Using the facultative root hemiparasite Rhinanthus minor and Hordeum vulgare as a host, the flows, depositions, and metabolism of abscisic acid (ABA) within the host, within the parasite, and between host and parasite have been studied. When the plants were supplied with 5 mM NO(3)(-), there were weak or no effects of parasitism on ABA flows, biosynthesis, and ABA degradation in barley. However, ABA deposition was significantly affected in the leaf laminae (3-fold) and in the leaf sheath (2.

Solute flows from Hordeum vulgare to the hemiparasite Rhinanthus minor and the influence of infection on host and parasite nutrient relations.

Using the facultative root hemiparasite Rhinanthus minor and Hordeum vulgare L. as a host, the flows and partitioning of mineral nutrients within the host, the parasite and between host and parasite have been studied during the study period 41-54 d after planting, i.e approximately 30-43 d after successful attachment of the parasite to the host.

Water flows in the parasitic association Rhinanthus minor/Hordeum vulgare.

Using the facultative root hemiparasite Rhinanthus minor and its host Hordeum vulgare several aspects of water relations have been measured in this parasitic association. Extraction of xylem sap by the parasite from the host's roots is facilitated by con siderably higher transpiration per leaf area in the parasite than in the host and by the fact that stomata of attached Rhinanthus were open all day and night despite extremely high ABA concentrations in the leaves. By comparison, another root hemiparasite, Melampyrum arvense, parasitizing various grasses in the field, showed normal diurnal stomatal behaviour.

Flows of elements, ions and abscisic acid in Ricinus communis and site of nitrate reduction under potassium limitation.

In a pot experiment Ricinus communis plants were cultivated in quartz sand and supplied daily with a nutrient solution which contained 4 mol m(-3) nitrate as the nitrogen source and either full strength potassium (1.3 mol m(-3), control) or 8% potassium (0.1 mol m(-3), K(+)-limitation).

Effect of top excision and replacement by 1-naphthylacetic acid on partition and flow of potassium in tobacco plants.

The effect of removal of the shoot apex of 92-d-old tobacco plants and its replacement by 1-naphthylacetic acid (NAA) on sink-source relationships and on the flows and partitioning of potassium and water has been studied over a short-term period of 7 d (intact control plants) or 8 d (decapitated and NAA-treated plants). For determining flows an upper, middle and lower stratum of three leaves each were analysed. Within the study period three new leaves were formed in control plants and 57.

Solute flux into parasitic plants.

Parasitic plants form intimate contacts with host tissue in order to gain access to host solutes. There are a variety of cell types within the host which parasitic plants could access to extract solutes. Depending on the degree to which the parasite has embraced the parasitic lifestyle, the extent of solute flux and the pathways used to transfer solutes from host to parasite will vary.

Foliar application of nitrate or ammonium as sole nitrogen supply in Ricinus communis. II. The flows of cations, chloride and abscisic acid.

Following a precultivation with pedospheric nitrogen nutrition, Ricinus plants were supplied with nitrogen solely by spraying nitrate or ammonium solution onto the leaves during the experimental period. The chemical composition of tissues, xylem and phloem exudates was determined and on the basis of the previously determined nitrogen flows (Peuke et al., New Phytologist (1998), 138, 657-687) the flows of potassium, sodium, magnesium, calcium, chloride and ABA were modelled.

Ion distribution in relation to leaf age in Leptochloa fusca (L.) Kunth* (Kallar grass) II. Anions*.

Using Leptochloa fusca (L.) Kunth (Kallar grass) plants, the distribution of Cl , NO , H PO , SO and malate between leaves of various ages has been studied. Plants grown in a reclaimed, salt-affected field, in solution culture and in soil at 10, 100 and 125 mM NaCl have been analyzed.

Ion distribution in relation to leaf age in Leptochloa fusca (L.) Kunth (Kallar grass): I. K, Na, Ca and Mg.

Using Leptochloa fusca (Kallar grass) plants, the distribution of K, Na, Mg and Ca between leaves of various ages has been studied. Plants grown in a salt-affected, reclaimed field, in a solution culture and in soil in pots at 10, 100 and 125 mM NaCl have been analyzed. Despite the presence of salt-secreting glands on Leptochloa fusca leaves, Na concentrations increased strongly with leaf age, while K concentrations were highest in young leaves and decreased with increasing leaf age.

Effects of transpiration on potassium and sodium fluxes in root cells and the regulation of ion distribution between roots and shoots of barley seedlings.

The effects of transpiration on uptake and xylem transport of K and Na and on the individual fluxes of these ions in root cells of barley seedlings (Hordeum distichon L., age 4.5 d) were studied.

Water transport in barley roots : Measurements of root pressure and hydraulic conductivity of roots in parallel with turgor and hydraulic conductivity of root cells.

Radial transport of water in excised barley (Hordeum distichon, cv. Villa) roots was measured using a new method based on the pressure-probe technique. After attaching excised roots to the probe, root pressures of 0.

Mesurement of longitudinal ion profiles in single roots of Hordeum and Atriplex by use of flameless atomic absorption spectroscopy.

A method is described by which the Na(+) and K(+) content in 0.5 mm sections of single roots of Hordeum distichon L. and Atriplex hortensis L.

K(+)-dependent net Na(+) efflux in roots of barley plants.

The influence of K(+) ions on the net Na(+) fluxes in cells of excised barley roots (Hordeum distichon L.) and roots of whole barley plants was investigated. The fluxes were determined by flame photometry in the external solution.

[On the light-dependent influx of ions in leaves of Elodea densa. Comparison of the influxes of K(+) and Cl (-) ions].

The light-dependent influxes of K(+) and Cl(-) in detached leaves of Elodea densa were measured using (36)Cl(-) and (42)K(+) or (86)Rb(+) as tracers.The K(+) and Cl(-) influxes were enhanced by light and also in the dark after a preillumination. The rate of influx decayed in the dark according to a first order reaction with a half-time of 25 or 27 sec.

[Effect of K(+) on Na (+) fluxes and transport in barley roots: K(+)-stimulated Na (+) efflux in the root cortex].

Barley roots grown on a nutrient solution containing 1 mM Na(+) but no K(+) are capable of a considerable Na(+) transport via the symplasm of the root and the xylem vessels. K(+) added to the medium surrounding the root cortex severely inhibits this transport after a lag period at a high rate constant (Fig. 3).

Evidence for a K(+)-stimulated Na (+) efflux at the plasmalemma of barley root cells.

The influence of K(+) on the Na(+) fluxes of barley root cells was investigated. A increased K(+) concentration (K(+) influx) results in a transient increase of the plasmalemma efflux of Na(+) followed by a decrease, and in a decrease of the cytoplasmic content and the tonoplast influx of Na(+). These results are consistent with a Na-K-pump at the plasmalemma.

[The influx of K(+) ions in leaves of Elodea densa, dependence on light, potassium concentration, and temperature].

1. The influx of potassium ions in leaves of Elodea densa during short periods of time was measured using (42)K and (86)Rb as tracers. The K(+) influx was linear with time (Fig.

[The Action of CO2 on the Light-dependent Cl(-)-Uptake by Elodea densa: Regulation between Noncyclic and Cyclic photophosphorylation].

The light curve of Cl(-)-uptake (uptake vs. light intensity) byElodea densa in pure N2 shows that saturation is reached at a very low light intensity. In N2+3% CO2, on the other hand, there is considerably less Cl(-) uptake.