Reproductive biology of a tropical catfish, Mystics nemurus Cuvier & Valenciennes, in Chenderoh reservoir, Malaysia

Abstract. The reproductive biology of a popular and abundant freshwater catfish, Mystus nemurus Cuvier & Valenciennes, was examined, including sex ratio, gonadosomatic index, ova diameter and fecundity. The numerical ratio of male to female was 1:1.06 and was not significantly different (P > 0.05). Mean female gonadosomatic indices (GSI) in April and September corresponding to north-east and south-west monsoons were significantly different (P < 0.05) from the dry season (May, June, July and August). Thus the apparent GSI maxima in April and September were indicative of peak spawning period. However, there were no significant differences (P > 0.05) in the fluctuation of the measure of GSI except for those in the dry months, which probably suggested the existence of a protracted breeding season. Mean male GSI in February and November were similarly significant (P < 0.05) to the dry season, although not statistically different (P > 0.05) from those of January, March, April, July, August, October and November. This was probably attributable to an extended breeding period with spawning peaks in February and November corresponding to early and late monsoons. The aseasonal reproduction is common in tropical fishes. GSI were positively correlated with rainfall and water level fluctuations. Fecundity varied from a minimum 6900 to a maximum 93510 in specimens with total lengths of 34.8cm and 45.0cm respectively. Fecundity was found to increase linearly with length and weight and was significantly different (P < 0.05) from them.     

Effects of red and blue LEDs on in vitro growth and microtuberization of potato single-node cuttings

The objectives of this study were to investigate the effects of red and blue LEDs on in vitro growth and microtuberization of potato (Solanum tuberosum) single-node cuttings. Explants were incubated under 6 light treatments: 100% red LEDs (R), 75% red LEDs+ 25% blue LEDs (3RB), 50% red LEDs+ 50% blue LEDs (RB), 25% red LEDs+ 75% blue LEDs (R3B), 100% blue LEDs (B) and white LEDs (W). Most of the growth and physiological parameters were significantly higher in 3RB than W. Enhancement of leaf area and chlorophyll concentrations were obtained in B. Leaf stomata were elliptical with the lowest density in 3RB. However, those in W were round in shape, and those with the smallest size and the highest density were observed in R. Most of the characteristics of microtuberization were also improved in 3RB. The combined spectra of red and blue LEDs increased the number of large microtubers. The fresh weight of individual microtubers in R and W were increased, but not their number. These results suggest that, of the treatments assessed, 3RB is optimal for the in vitro growth of potato plantlets and the combination of red and blue LEDs is beneficial for microtuberization.     

Quality and Crop Yield Potential of Moderately Degraded Alfisols Under Different Nutrient Inputs and Cropping Patterns

Crop performance on degraded soil needs special management practices to overcome soil quality limitations. In a 2-year(from summer 2006 to winter 2007–2008) field trial on a moderately degraded Alfisol in Swabi District(34°7′12′′N, 72°28′20′′E), Pakistan,the effects of three cropping patterns, cereal-cereal(CC), cereal-legume(CL), and cereal-cereal and legume intercrop(CLI), were tested in main plots under four fertilization treatments in sub-plots, including no fertilization(control), farmers' practice(FP, 60:45 kg ha~(-1) N:P_2O_5), recommended dose(RD, 120:90:60 kg ha~(-1) N:P_2O_5:K_2O), and integrated nutrient management(INM, 20 t ha~(-1) farmyard manure integrated with 50% N, 100% P, and K of recommended dose), using a split-plot randomized complete block design. The performance of CL was superior than CC in plant height, leaf area index(LAI), cob length, grain yield, biological yield, and grain protein(8%, 26%, 8%, 5%, 10%, and 8% increases, respectively), while CLI confirmed significant improvement only in LAI(25%) over CC. Response to nutrient inputs from all sources was in the order of INM RD FP control, and the maximum net economic return by INM(23% and 2.5 times higher than RD and FP, respectively) indicated severe deficiency of both macro-and micro-nutrients in the soil as well as degraded physical properties. Increases in soil organic matter, total N, total mineral N, available P and K, total porosity, and available water-holding capacity by 6%, 34%, 24%, 50%, 13%, 5%, and 7%, respectively, and decrease in soil bulk density by 4% after four crop seasons indicated optimistic changes in soil quality as a result of the combined effects of fertilization from organic and inorganic sources and legumes within crop rotation. This study suggests that keeping the soil covered under cereal-legume rotation crops all year round and treatment with INM(50% N from organic source and 50% from inorganic source) are the best management practice for sustained production on degraded Alfisols.     

Pharmacokinetics and urinary excretion of sulphadimidine in sheep and goats

Pharmacokinetics and urinary excretion of sulphadimidine were determined in sheep and goats following a single intravenous injection (100 mg/kg). The disposition of the drug was described in terms of exponential expression: C _p= Be ^-βt. Based on total (free and bound) sulphonamide level in plasma, pseudo-distribution equilibrium was rapidly attained and the half-life for elimination was 3.88 ± 0.64 h and 4.00 ± 0.34 h in sheep and goats, respectively. Body clearance, which is the sum of all clearance processes was 88 ± 19 and 55 ± 4 ml/kg/h in sheep and goats. Based on this study a satisfactory intravenous dosage regimen might consist of 100 and 60 mg sulphadimidine/kg body wt for sheep and goats and should be repeated at 12 h intervals. The influence of disease conditions on predicted plasma levels remain to be verified experimentally. Three-quarters of an intravenously injected dose of sulphadimidine was excreted in the urine of sheep and goats within 24 h of administration. The drug was mainly excreted as free amine while acetylated drug constituted 7 and 8% of total drug content in the urine of sheep and goats, respectively.     

Residues of atrazine and its metabolites after prolonged usage

Residus d'atrazine el de ses metabolites après une utilisation prolongée De I'atrazine a été appliquée dans un champ cultivé en maïs (Zea mays L.) pendant 20 annees consecutives, a des doses allant de 1.40 a 2.24 kg/ha. L'analyse d'échantillons de sol prélevés 6 et 12 mois après la derniere application a révélé la presence de residus du produit et de ses analogues hydroxy monodealkyles. Les jeunes pousses et les racines de plantes d'avoine (Avena saliva L.) cultivees dans le champ contenaient de l'hydroxytriazine (2-hydroxy-4-éthylamino-6-isopropyl-amino-i-triazine) et l'un de ses analogues monodealkyles sous la forme conjuguée. De l'avoine et de la fléole (Phleum pralense L.), cultivees sur le sol traité, dans une chambre de culture, donnèrent des resultats analogues. Les resultats suggèrent que les applications d'atrazine répétées a long terme annuellement pour le désherbage du maïs conduisent a la persistance dans le sol de certains de ses produits de degradation, principalement des analogues hydroxylés, un an apres la derniere application d'herbicide. Il est concevable que de tels résidus puissent pénétrer dans les cultures vivrières implantées dans un sol traite a 1'atrazine, dans 1'année ou les annees qui suivent la cessation d'un traitement a long terme.     

Bound and extractable 14C residues in canola (Brassica napus) plants treated with radiolabelled atrazine

The nature and distribution of ¹⁴C atrazine (2- chloro- 4 -ethylamino- 6 -isopropylamino-s-tria- zine) residues in resistant and susceptible canola (Brassica napus L.) varieties were studied. Radiolabelled atrazine was applied to the plants just before the flowering stage and continued for 10 days. The plants were harvested 3, 10 and 25 days after the end of the treatment. The roots, shoots and pods of each plant were exhaustively extracted with methanol. The ¹⁴C distribution between the methanol extracts and the plant matrix fractions (bound residues) was similar for the two varieties. High-pressure liquid Chromatographie analysis of the methanol extracts showed that they contained two unknown metabolites (possibly conjugates) in addition to atrazine. The bound ¹⁴C residues were released by supercritical methanol extraction and analysed by thin-layer chromato- graphy, gas chromatography and high-pressure liquid chromatography. Several ¹⁴C components in the released material were detected. Bound atrazine and its two dealkylated metabolites represented only a very small portion (10–18%) of the total bound ¹⁴C residues in the plants. Résidus ¹⁴C extractibles et liés chez des plantes de canola (Brassica napus) traitées avec de l'atrazine radioactivement marquée La nature et la distribution de résidus d'atrazine ¹⁴C (2-chloro 4-ethylamino-6-isopropylamino-s-triazine) chez des variétés de canola résistantes et sensibles ont étéétudiés. De l'atrazine radiomarquée a été appliquée aux plantes juste avant la floraison et poursuivie pendant 10 jours. Les plantes ont été récoltées 3, 10 et 25 jours après la fin du traitement. Les racines, tiges et gousses de chaque plante ont été complètement extractées avec du methanol. La distribution du ¹⁴C entre les extraits méthanol et les fractions de plantes matricielles (liées) a été similaire pour les 2 variétés. Des analyses HPLC des extraits méthanol ont montré qu'ils contenaient deux metabolites inconnus (probablement combinés) en plus de l'atrazine. Les résidus ¹⁴C liés étaient libérés par une extraction au méthanol supercritique et analysé par Chromatographie en couche mince, Chromatographie gazeuze et HPLC. Plusieurs composés dans le matériel libéré ont été détectés. L'atrazine liée et ses deux metabolites dealklyés représentaient seulement une très petite part (10–18%) de la totalité des résidus ¹⁴C liés dans les plantes. Gebundene und extrahierbare ¹⁴C-Rückstände in mit radioaktiv markiertem Atrazin behandeltem Raps (Brassica napus) Die Art und die Verteilung von Rückständen von ¹⁴C-Atrazin (2-Chlor-4-ethylamin-6-iso- propylamin-s-triazin) wurden in resistenten und empfindlichen Varietäten von Raps (Brassica napus) untersucht. Das radioaktiv markierte Herbizid wurde kurz vor der Blüte und 10 Tage weiter auf die Pflanzen ausgebracht. Die Pflanzenproben wurden 3, 10 und 25 Tage nach dem Ende der Behandlung gezogen. Wurzeln, Sprosse und Schoten wurden erschöpfend mit Methanol extrahiert. Die ¹⁴C-Verteilung in den Methanolextrakten und im Pflanzenmaterial (gebundene Rückstände) war bei beiden Sorten ähnlich. Bei der HPLC-Analyse wurden in den Methanolextrakten neben Atrazin 2 unbekannte Metaboliten (vermutlich Konjugate) gefunden. Die gebundenen ¹⁴C-Rückstände wurden im Überkritischen Verfahren mit Methanol extrahiert und dünnschicht-, gas-und HPL-chromatographisch analysiert. Verschiedene ¹⁴C-Verbindungen wurden gefunden. Gebundenes Atrazin und seine beiden de-alkylierten Metaboliten machten nur eine kleinen Anteil (10 bis 18%) der gesamten gebundenen ¹⁴C-Rückstände aus.     

堆肥, 石灰和磷酸二铵对铜尾矿土壤重金属的植物有效性的影响

Soil samples from a historic copper mine tailing site at the Parys Mountain,North Wales (UK) were amended with green waste compost (GC),GC+30% sewage sludge (GCS),lime and diammonium phosphate (DAP),to determine the effect of amendments on DTPA-and Ca (NO₃) ₂-extractable metals in the mine tailing and on the phytoavailability of heavy metals by a lettuce (Lactuca sativa L.).Both compost were added at the rate of 10% by weight,lime was added as calcium carbonate equivalent (pH = 7) and DAP at a 2300 mg kg^-1 soil level.The experiment was arranged in randomised complete design with three replicates in pots under control environment.Addition of lime resulted in the largest reduction in metal extractability with DTPA and Ca (NO₃) ₂ and phytoavailability of Cu,Fe and Zn while DAP was effective in lowering Pb extractability and phytoavailability.With exception of Zn,all other metals extracted decreased with time after amendment applications.The distribution of heavy metals between and within the four procedures of potentially bioavailable sequential extraction (PBASE) varied significantly (P < 0.001).Stronger relationships were noted between the metals extracted with PBASE SE1 and Cu,Pb (P < 0.01) and Fe (P < 0.001) in the lettuce.These results indicate that addition of lime is sufficient to restore the vegetative cover to a high metal mine waste while DAP is good for stabilizing Pb,but its detrimental role on plant growth and the risk associated with presence of N in DAP (through N leaching) may restrict its chances for remediation of contaminated sites.     

Total sulphur amino acid requirement and cystine replacement value for fingerling rohu,Labeo rohita: effects on growth,nutrient retention and body composition

Two feeding experiments were conducted to quantify the total sulphur amino acid (TSAA) requirement and replacement value of cystine for methionine for fingerling Labeo rohita. In Experiment I, isonitrogenous (380 g kg^?1 CP) and isocaloric (17.90 kJ g^?1 GE) amino acid test diets with graded levels of methionine (4, 6, 8, 10, 12, 14 g kg^?1 dry diet) and 0.4 g kg^?1 cystine were fed to fish (4.62 ± 0.2 cm; 0.66 ± 0.1 g) and methionine requirement determined by analysing absolute weight gain (AWG) (5.48), feed conversion ratio (FCR) (1.26), protein retention efficiency (PRE%) (39%) and energy retention efficiency (ERE%) (85%) data which were best at 10 g kg^?1 methionine of dry diet. In Experiment II, six diets with different ratios of L‐cystine and L‐methionine on equimolar sulphur basis were fed to fish (4.71 ± 0.1 cm; 0.69 ± 0.2 g) under identical conditions. Maximum AWG (5.58), best FCR (1.24), PRE (41%) and ERE (86%) in fish fed Diet IV indicated cystine replacement value to be 40%. On the basis of the broken‐line and second‐degree polynomial regression analyses of results obtained in Experiments I and II, it is concluded that inclusion of TSAA in the range of 25.2–31.31 g kg^?1 of protein is optimum of which 33–39% could be spared by cystine.     

Biology of milk thistle (Silybum marianum) and the management options for growers in north-western Pakistan

Milk thistle ( Silybum marianum ) is cultivated as a medicinal plant but it also can be a troublesome weed. It is an annual or biennial herb that prefers high rainfall and fertile soils. Milk thistle has become a widespread weed in north-western Pakistan, where it causes yield reductions ≤37% in wheat and poses harvesting problems due to its thorny nature. Shortcomings in cultural practises, such as a low crop seed rate, wide row spacing, broadcast fertilizer, and limited crop rotation have contributed to milk thistle becoming a severe weed problem for farmers in this region. This paper reviews the biology of milk thistle and discusses the possible management options for its control, considering the socioeconomic conditions of farmers in Pakistan.