An evaluation of the Olsen test as a measure of plant-available phosphorus in grassland soils derived from basalt parent material

Abstract. Anecdotal and circumstantial evidence have suggested that the Olsen test underestimates plant-available phosphorus (P) in basaltic soils in Northern Ireland. Therefore, the ability of this test to predict plant-available P in basaltic (and non-basaltic) soils was investigated by regressing Olsen-P data against herbage P indices calculated from plant tissue test data using the diagnosis and recommendation integrated system. The average Olsen-P concentration for a range of fields situated on basaltic soils was considerably lower than the average Olsen-P concentration for a range of fields situated on non-basaltic soils, and yet mean sward P status, as given by the herbage P indices, was similar for both groups of fields. Herbage P indices were also much better correlated with Olsen-P measurements in non-basaltic soils than in basaltic soils. Furthermore, at low Olsen-P values (≶9mgPL⁻¹) some swards on basaltic soils were genuinely deficient in P, while others were sufficient or even in surplus for this nutrient. The results confirm that Olsen-P is inadequate as a predictor of plant-available P in basaltic soils. It is concluded that an alternative soil test is needed to provide a reliable assessment of plant-available P in basaltic soils, to prevent overuse of fertilizer and manure P and to minimize the amounts of P entering local watercourses.     

Doxorubicin affects the cardiac muscarinic system in the rat.

During the study on the mechanism of doxorubicin-induced cardiotoxicity, we observed that a long incubation (4 hr) with doxorubicin reduced the maximal negative inotropic effects of a muscarinic receptor agonist, carbachol. The mechanism responsible for this doxorubicin-induced reduction of the efficacy of carbachol was examined in isolated guinea pig hearts. In isolated left atrial muscle preparations, 1 hr incubation with 100 microM doxorubicin caused a parallel right-ward shift of the concentration-response curves for carbachol, but a longer (4 hr) incubation with this agent (30, 100 or 200 microM), caused a significant reduction of the magnitude of the negative inotropic effect of carbachol in addition to the concentration-dependent parallel right-ward shift. The 4-hr incubation with these concentrations of doxorubicin also reduced the maximal negative inotropic effect of an adenosine A1 receptor agonist, R-phenylisopropyl adenosine (R-PIA), without affecting the potency of this agonist. Doxorubicin (1 to 100 microM) reduced [3H]quinuclidinyl benzilate (QNB) binding in a concentration dependent manner, but failed to alter [3HIR-PIA binding. The decrease in the magnitude of the maximal negative inotropic effect by doxorubicin was caused by changes in the muscarinic system at steps common to the transduction of muscarinic and adenosine A1 receptor mechanisms.     

Reproduction in three species of rainbowfish (Melanotaeniidae) from rainforest streams in northern Queensland, Australia

Abstract – The reproductive biology of three species of rainbowfish (Melanotaeniidae) in northeastern Australian rainforest streams was investigated. Two species, Melanotaenia eachamensis and Cairnsichthys rhombosomoides are endemic to the area, whereas the third, M. splendida splendida, is more widespread. The species were all highly fecund, producing many hundreds of eggs between 1.10 and 1.24 mm in diameter. Melanotaenia eachamensis was the most fecund, produced the largest eggs of the three species, and consequently exhibited the greatest maternal investment (as measured by gonadosomatic index). The majority of reproductive effort occurred during the dry season, although reproductively active fish were present year-round for each of the species, but particularly so for M. s. splendida and C. rhombosomoides. No evidence for a role by temperature or photoperiod as environmental cues for reproduction was found, and it was suggested that gonad development was strongly tied to somatic growth. The concentration of reproduction to the dry season ensures that larvae are produced during a period of relatively stable and benign physical conditions. Comparison of temporal changes in gonadosomatic index values suggest that the spawning season of M. eachamensis , which occurs in high-elevation streams, is more restricted and commences about 1 month earlier than either other species. A similar phenology was observed for the M. s. splendida population found at high elevation and highlights the potential for spatial differences in stream productivity to influence life history. ^Note     

Validation of the otoliths for age determination in Barbus sclateri (Günth.)

Abstract – Otoliths were used to explore the timing of annulus formation in Barbus sclateri. Lapillus exhibited opaque and translucent zones whose combination was formed once a year. Opaque zones appeared formed from July and January, and the translucent ones from February to June. We describe a procedure to assess age by using the number of annulii, the condition of the otolith's edge and the capture date. The use of otoliths for age determination in this cyprinid endemic to the Iberian Peninsula provides a useful alternative to the traditional methods of scale reading. ^Note     

Evaluation of two N cycle models for the prediction of N mineralization from grassland soils in the UK

Abstract. The ability of two nitrogen cycle models, of contrasting complexity, to predict N mineralization from a range of grassland soils in the UK, was evaluated. These were NCYCLE, a simple mass balance model of the N cycle in UK grasslands, and CENTURY, a more complex model simulating long-term C, N, P & S dynamics in grassland ecosystems. The models were tested using field measurements of net N mineralization from a range of grassland soils (differing in soil type, history & management practice), obtained over a 2 year period using a soil core incubation technique. This method was considered to measure the total net release of mineral N from the soil organic matter over a specified time, including N which may have been recycled several times. NCYCLE consistently under-estimated mineralization rates at all sites. By contrast, there was some correlation between CENTURY predictions of net N mineralization and field measurements. This may have reflected the different abilities of the two models to simulate N recycling. Neither model, however, was able to predict adequately the effect of cultivation and reseeding on net N mineralization.     

Mid-storage and pre-sowing seed treatments for lettuce and carrot

Mid-storage hydration-dehydration treatments with medium-vigour lettuce seed very effectively reduced physiological deterioration in storage and ultimately showed better field emergence and final yield. Soaking-drying treatment of high-vigour lettuce seed was not effective. Pre-sowing treatment of medium-vigour lettuce seed, though less effective than mid-storage treatment, gave better field performance, but high-vigour seed did not benefit from the treatment. For carrot, both mid-storage and pre-sowing seed treatments proved beneficial, with the former showing better performance than the latter. Unlike lettuce, well-preserved carrot seed responded positively to the pre-sowing treatment.     

The extent of genetic diversity among Vanilla species: Comparative results for RAPD and ISSR

Vanilla is a large genus of about 110 species in the orchid family (Orchidaceae), including the species Vanilla planifolia from which commercial vanilla flavoring is derived. Since most species of vanilla are considered rare and endangered there is an urgent need to conserve them through genetic analysis and propagation/conservation studies on this crop.The present study investigated the genetic diversity among nine leafy- and leaf-less Vanilla species employing 30 decamer RAPD primers and 10 ISSR primers. The species under study were diverse and displayed a range of variability (0–66% and 0–81% for RAPD and ISSR, respectively). A total of 154 RAPD polymorphic markers (83.24%, h = 0.378) and 93 ISSR polymorphic markers (86.11%, h = 0.363) were used to generate a genetic similarity matrix followed by the cluster analysis. Specific groupings were revealed by each cluster analysis with slight variation between two different markers. Among the nine species studied, V. planifolia, Vanilla aphylla and Vanilla tahitensis revealed very low level of variation within their collections, thus indicating a narrow genetic base. The large genetic distance of Vanilla andamanica from other species suggests its different origin. A close genetic affinity was observed between the pairs V. planifolia, V. tahitensis and Vanilla albida, V. aphylla. These are the first comparative results for RAPD and ISSR reporting inter-relationship among nine cultivated, wild and hybrid Vanilla species.