Root-induced changes in the rhizosphere may affect mineral nutrition of plants in various ways. Examples for this are changes in rhizosphere pH in response to the source of nitrogen (NHrN versus N03-N), and iron and phosphorus deficiency. These pH changes can readily be demonstrated by infiltration of the soil with agar containing a pH indicator. The rhizosphere pH may be as much as 2 units higher or lower than the pH of the bulk soil. Also along the roots distinct differences in rhizosphere pH exist. In response to iron deficiency most plant species in their apical root zones increase the rate of H+ net excretion (acidification), the reducing capacity, the rate of Fe"' reduction and iron uptake. Also manganese reduction and uptake is increased several-fold, leading to high manganese concentrations in iron deficient plants.Low-molecular-weight root exudates may enhance mobilization of mineral nutrients in the rhizosphere. In response to iron deficiency, roots of grass species release non-proteinogenic amino acids (,,phytosiderophores") which dissolve inorganic iron compounds by chelation of Fe'" and also mediate the plasma membrane transport of this chelated iron into the roots.A particular mechanism of mobilization of phosphorus in the rhizosphere exists in white lupin (Lupinus albur L.). In this species, phosphorus deficiency induces the formation of so-called proteoid roots. In these root zones sparingly soluble iron and aluminium phosphates are mobilized by the exudation of chelating substances (probably citrate), net excretion of H+ and increase in the reducing capacity. In mixed culture with white lupin, phosphorus uptake per unit root length of wheat (Triticurn aestivurn L.) plants from a soil low in available P is increased, indicating that wheat can take up phosphorus mobilized in the proteoid root zones of lupin.At the rhizoplane and in the root (root homogenates) of several plant species grown in different soils, of the total number of bacteria less than 1 % are Nz-fixing (diazotrophe) bacteria, mainly Enterobacter and Klebsiella. The proportion of the diazotroph bacteria is higher in the rhizosphere soil. This discrimination of diazotroph bacteria in tHe rhizosphere is increased with foliar application of combined nitrogen. Inoculation with the diazotroph bacteria Azospirillurn increases root length and enhances formation of lateral roots and root hairs similarly as does application of auxin (IAA). Thus rhizosphere bacteria such as Azospirillurn may affect mineral nutrition and plant growth indirectly rather than by supply of nitrogen. Wurzel-induzierteVeriinderungen in der Rhizosphiire: Bedeutung fib die Miuernlstoffernhng der Wanzen Durch von Wurzeln induzierte Veranderungen in der Rhizosphare kann die Mineralstoffernahrung der Pflanzen in verschiedener Weise beeinfluRt werden. In der vorliegenden Arbeit werden dafir Beispiele gegeben. Veranderungen des Rhizospharen-pH-Wertes konnen in Abhangigkeit von der 06Ce3263186/040&?-0441 $02.5010 0 VCH Vcrlagsgesellschaft mbH, D-6940 Weinheim, 1986 442 Marsc...

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What does it mean to ‘drop out’ of therapy? Many definitions of ‘dropout’ have been proposed, but the most widely accepted is the client ending treatment without agreement of their therapist. However, this is in some ways an external criterion that does not take into account the client’s experience of therapy, or reasons for ending it prematurely. This study aimed to identify whether there were more meaningful categories of dropout than the existing dropout definition, and to test whether this refined categorization of dropout was associated with clinical outcomes. This mixed-methods study used a subset of data from the IMPACT trial, which investigated psychological therapies for adolescent depression. Adolescents were randomly allocated to a treatment arm (Brief Psychosocial Intervention; Cognitive-Behavioral Therapy; Short-Term Psychoanalytic Psychotherapy). The sample for this study comprised 99 adolescents, aged 11–17 years. Thirty-two were classified as having dropped out of treatment and participated in post-therapy qualitative interviews about their experiences of therapy. For 26 dropout cases, the therapist was also interviewed. Sixty-seven cases classified as having completed treatment were included to compare their outcomes to dropout cases. Interview data for dropout cases were analyzed using ideal type analysis. Three types of dropout were constructed: ‘dissatisfied’ dropout, ‘got-what-they-needed’ dropout, and ‘troubled’ dropout. ‘Dissatisfied’ dropouts reported stopping therapy because they did not find it helpful. ‘Got-what-they-needed’ dropouts reported stopping therapy because they felt they had benefitted from therapy. ‘Troubled’ dropouts reported stopping therapy because of a lack of stability in their lives. The findings indicate the importance of including the perspective of clients in definitions of drop out, as otherwise there is a risk that the heterogeneity of ‘dropout’ cases may mask more meaningful distinctions. Clinicians should be aware of the range of issues experienced by adolescents in treatment that lead to disengagement. Our typology of dropout may provide a framework for clinical decision-making in managing different types of disengagement from treatment.

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