Properties of crosslinked waterborne polyurethane adhesives with modified melamine: Effect of curing time, temperature, and HMMM content

A series of crosslinked waterborne polyurethane (WBPU) adhesives were prepared by prepolymer synthesis. Modified melamine, hexamethoxymethyl melamine (HMMM) was used as the crosslinking agent. It was elucidated by FTIR and ¹H-NMR spectroscopy that the crosslinking reaction occurred between the polyurethane carboxyl acid salt groups and the HMMM methoxy groups. The hydrophobicity of the WBPU films increased after HMMM crosslinking. As the HMMM content was increased (increasing mole ratio of HMMM/dimethylol propionic acid (DMPA)), the water uptake (%) of the film decreased, and the water contact angle increased. The thermal stability, tensile strength, and initial modulus increased with increasing HMMM content up to an optimum value (mole ratio of HMMM/DMPA=0.5) at which point the maximum thermal stability, tensile strength, and initial modulus were recorded. The adhesive strength was found to be dependent on HMMM content, curing time, and temperature. The adhesive strength of crosslinked WBPU in the case of optimum HMMM content (8.46 wt%) was only slightly affected after immersing adhesive bonded nylon fabrics in water (for up to 2 days).     

Development of Chromosomal Segment Substitution Lines from a Backcross Recombinant Inbred Population of Interspecific Rice Cross

Genetic variation in cultivated rice has been reduced tremendously during domestication and modern plant breeding. As a consequence, slow progress in rice breeding and genetic vulnerability in rice production has been witnessed since 1980s. Wild relatives of cultivated rice remain to be highly diversified and hold various genes conferring resistance to biotic and abiotic stresses, thus providing a valuable gene pool for rice genetic improvement. More and more attentions have been paid to intro…     

Nitrogen transformation and carbon sequestration in wetland paddy field of Bangladesh

Paddy and Water Environment - Rice-based cropping systems in Bangladesh have received little consideration of changing nitrogen (N) and carbon (C) in soil. Therefore, this study was conducted at...     

Production of phenolic compounds in hairy root culture of tartary buckwheat (Fagopyrum tataricum Gaertn)

Fagopyrum tataricum Gaertn (tartary buckwheat) is an excellent medicinal and nutrient-rich crop. It has a high content of rutin and other phenolic compounds. An experiment was conducted to investigate in vitro production of phenolic compounds from hairy root culture of tartary buckwheat. Hairy root growth was promoted by increasing culture time in MS medium. The highest hairy root growth reached up to 11.2 g/l dry weight at 18 d after placement. Transformation was confirmed by PCR using rol genes, rol A (304 bp), B (797 bp), C (550 bp), and D (1035 bp) genes which is transferred into hairy roots from the Ri-plasmid in Agrobacterium rhizogenes and is responsible for the induction of hairy root from plant species. Rutin, quercetin, (−) epicatechin, (−) catechin hydrate, gallic acid, ferulic acid, chlorogenic acid, and caffeic acid were identified both in hairy and wild type roots of tartary buckwheat. The main compound found in the both types of root was epicatechin followed by rutin. The concentration of phenolic compounds in the hairy roots of tartary buckwheat was several-fold higher compared with wild type roots of same species. Our results indicate that hairy root culture of F. tataricum is a valuable alternative approach for the production of phenolic compounds.     

Quantitative trait loci (QTL) mapping of silique length and petal colour in Brassica rapa

Recombinant inbred lines (RILs) derived from a cross between Brassica rapa L. cv. ‘Sampad’, and an inbred line 3‐0026.027 was used to map the loci controlling silique length and petal colour. The RILs were evaluated under four environments. Variation for silique length in the RILs ranged from normal, such as ‘Sampad’, to short silique, such as 3‐0026.027. Three QTL, SLA3, SLA5 and SLA7, were detected on the linkage groups A3, A5 and A7, respectively. These QTL explained 36.0 to 42.3% total phenotypic variance in the individual environments and collectively 32.5% phenotypic variance. No additive × additive epistatic interaction was detected between the three QTL. Moreover, no QTL × environment interaction was detected in any of the four environments. The number of loci for silique length detected based on QTL mapping agrees well with the results from segregation analysis of the RILs. In case of petal colour, a single locus governing this trait was detected on the linkage group A2.     

Management strategy,uptake and translocation of nitrogen in tidal flooded rice ecosystem

Abstract

Enhancing rice yield is a great challenge for rice growers in the tidal flooded ecosystem, where poor agronomic management is one of the major constrains. Improve management practice (IMP) was compared with traditional farmers’ practice (TFP) in evaluating rice productivity, nutrient uptake, translocation and farm income in tidal flooded ecosystem. Results revealed that, IMP significantly produced higher number of panicles m^?2, more grain panicle^?1 and better grain filling. The rice cultivars produced 2.0 to 2.5 t grain ha^?1 with TFP, while 3.0 to 4.0 t ha^?1 with IMP. In different rice cultivars, the grain yield in IMP increased 12 to 60% over TFP. Similarly, the grains in IMP treatment absorbed 21.41 to 57.03?kg N ha^?1 whereas only 15.85 to 46.94?kg N ha^?1 in TFP plot. However, higher nitrogen (N) transfer from shoot to grain in IMP also suggests that the amount of N in soil was too low to meet the plant demand in TFP. Although, the IMP involved additional cost, but it gave significantly higher gross return (438 to 954?US$ha^?1) and margin (397 to 913?US$ha^?1) which added farm income upto 225?US$ha^?1 over TFP. Hence, it could be concluded that IMP is a potential option for increasing grain yield and farm income during aman season in the tidal flooded ecosystem.     

Determination of Poly-β-hydroxyalkanoate in Peat

Poly-β-hydroxyalkanoate (PHA) is a prokaryotic energy reserve material that has been used as an indicator of environmental stress in aquatic bacteria. The following technique has been used to quantify PHA in peatland microorganisms. Peat samples were dried, digested in sulphuric acid to convert PHA into crotonic acid, and the resulting acid determined using organic acid high performance liquid chromatography (HPLC) and ultraviolet (UV) detection at 214 nm. This technique is suggested to have potential value as an indicator of environmental stress on peatland microorganisms, such as that caused by summer drought, or changes in soil nutrient availability, which are predicted consequences of climatic change.     

Plant density and nitrogen effects on growth dynamics,light interception and yield of maize

Maize (Zea mays L.) growth and yield are most sensitive to variations in plant density and nitrogen (N) in north-western Pakistan. This study was conducted on the Agricultural Research Farm of NWFP (North West Frontier Province) Agricultural University, Peshawar, from 2002–2004 to establish an accurate plant density and N management system aimed at high yield of maize. The 2 × 3 × 6 factorial experiment was designed having two plant densities (P1 = 60,000 and P2 = 100,000 plants ha^?1) and three nitrogen rates (N1 = 60, N2 = 120 and N3 = 180 kg N ha^?1) applied to the main plots, while six split application for N in different proportions were applied to subplots at different growth stages of maize in two equal (S1), three equal (S2), three unequal (S3), four equal (S4), five equal (S5) and five unequal splits (S6) at sowing and with 1st, 2nd, 3rd and 4th irrigation at two-week intervals. Growth rate and yield increased with elevated dose and number of N split applications. Improved endurance to high stands allowed maize to intercept and use solar radiation more efficiently, contributing to the remarkable increase in the crop growth rate and yield.     

Expression and inheritance of isozymes in Brassica species and in their interspecific hybrids

Abstract

Gene expression was analysed by means of isozyme electrophoresis for three diploid species Brassica rapa (genome AA), B. nigra (BB), and B. oleracea/ B. oleracea var. alboglabra (CC), three amphidiploids B. juncea (AABB), B. napus (AACC) and B. carinata (BBCC), and in 15 interspecific hybrids from crosses within and between the diploids and the amphidiploids. Five enzyme systems were assessed: glucosephosphate isomerase, leucine aminopeptidase, phosphoglucomutase, 6-phosphogluconate dehydrogenase and malate dehydrogenase. Alleles descending from the diploid species were found both in natural and artificially produced amphidiploids. No effect of reciprocal crosses was observed. i.e., the Brassica isozymes were under nuclear gene control. Mendelian segregation in the F₂ generation from crossing two resynthesized B. napus was observed for the loci glucosephosphate isomerase-2 and phosphoglucomutase-3. Genome-specific alleles were identified for several loci. No alteration in the allelic expression of isozymes was found when assembling all three Brassica genomes in the trigenomic interspecific hybrids. Moreover, trigenomic hybrids were capable of disclosing a silent allele of leucine aminopeptidase from B. carinata, and thus in this study the capability of isozyme analysis for detecting hidden variation was demonstrated.