Sawfish exploitation and status in Bangladesh

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Controlling the Properties of OPEFB/PLA Polymer Composite by Using Fe<Subscript>2</Subscript>O<Subscript>3</Subscript> for Microwave Applications

Microwave-absorptive polymer composite materials provide protection against interference to communication systems caused by microwave-inducing devices. Microwave-absorptive polymer composites were prepared from polylactic acid (PLA) biocomposite blended with oil palm empty fruit bunch (OPEFB) fiber and commercial Iron oxide (Fe₂O₃) as filler using the melt-blending method. The composites characterization was carried out using the scanning electron microscopy (SEM) and X-ray diffraction (XRD) analyses. The coefficient of reflection S₁₁ and coefficient of transmission S₂₁ of the composites for various Fe₂O₃ filler percentages were determined using a rectangular waveguide in connection with microwave vector network analyser (HP/Agilent model PNA N5227). These coefficients were then used to calculate microwave-absorption properties (in decibels). XRD analysis showed that increasing amounts of reinforced material (Fe₂O₃) reduces the crystallinity of the composites. SEM data indicated that Fe₂O₃ filler ratio increased in the composites, and adhesion to the cellulose fiber grew gradually until the highest percentage of filler was added. The complex relative permittivity and relative permeability were obtained within the broad frequency range of 8–12 GHz at room temperature for various percentages of filler and were measured by the transmission/reflection method using a vector network analyser. Fe₂O₃ embedment in OPEFB/PLA was observed to have resulted in enhancing the dielectric and magnetic properties. The values of permittivity and permeability increased with increasing Fe₂O₃ filler content. Theoretical simulation studied the relation between ε′ and ε″ of the relative complex permittivity in terms of Cole-Cole dispersion law. The result indicated that the processes of Debye relaxation in Fe₂O₃/OPEFB/PLA, the unique dielectric characteristics of Fe₂O₃ cannot be accounted for by both the Debye dipolar relaxation and natural resonance. Results further showed that the material transmission, reflection, and absorption properties could be controlled by changing the percentage of Fe₂O₃ filler in the composites.     

Isolation and identification of indigenous marine diatoms (Bacillariophyta) for biomass production in open raceway ponds

For the successful, large‐scale cultivation of microalgae, which for our work refers to diatoms, it is important to select the appropriate species for the right environment. Intensive research on the growth of different strains of microalgae from several regions worldwide is an ongoing effort. The aim of our research in this context was to select the best isolates of diatoms from different coastal sites in Oman, a region whose flora is poorly known, and identify these species using molecular (nuclear‐encoded small subunit ribosomal RNA and chloroplast‐encoded rbcL and psbC) and morphologic data. We aimed also to investigate and measure the growth rate, biomass production and fatty acid composition under ambient environmental conditions. Our results showed that in contrast to most of the research reported in the literature, the production of biomass from six isolates has been successfully carried out with reduced amounts of nutrients and without CO₂ addition. Growth rates for species cultivated outdoors were high and ranged from 0.37 to 0.92 day^?1. These findings are economically very promising as fast growth rates, associated with reduced operational costs, could remarkably improve the production efficiency and thereby justify their use as biomass feedstocks. Molecular data revealed that one isolate was Bellerochea malleus, four isolates represented an unidentified species of Bellerochea and the remaining strain studied represented an unidentified species of the genus Nitzschia. These six strains were rich in polyunsaturated fatty acids, with an average of 47% of the total fatty acids, confirming their potential use as aquaculture feed supplements.     

Heat stress and plant development: role of sulphur metabolites and management strategies

Temperature plays a crucial role in plants development whereas a sudden rise may cause severe consequences. Heat stress impairs plant growth, photosynthesis, pollen development and reproduction. The plant photosynthetic efficiency is mainly reduced by the over production of reactive oxygen species, denaturation of heat shock proteins and alteration in many enzymes activities. Unlike drought stress, plants have developed a very few mechanisms to encounter heat stress problem. Recently, the use of nutrients such as sulphur has emerged as one of the efficient methods to enhance plant tolerance against high temperature stress. The mechanistic understanding of sulphur-based strategies could be very helpful to sustain plant development and global food supplies in future hotter climates. The present review mainly focuses on (1) high temperature induced changes in plant functions, (2) possible roles of sulphur metabolites in heat stress tolerance and (3) possibilities of using sulphur as a management strategy. Moreover, the review consolidates the future research needs that must focus on (i) heat tolerant germplasm screening; (ii) sulphur dose optimisation, application method and crop growth stages response; (iii) finding of sulphur induced heat tolerance mechanisms and (iv) the use of omic approaches to discover sulphur metabolites role in heat stress tolerance.     

Clutch size decisions of <Emphasis Type="Italic">Cotesia glomerata</Emphasis>, a gregarious parasitoid of <Emphasis Type="Italic">Pieris brassicae</Emphasis>

This work investigated the ability of the gregarious larval endoparasitoid Cotesia glomerata L. (Hymenoptera: Braconidae) to adjust the progeny sex ratio and clutch size with repeated oviposition experience and the effect of a honey-based diet on the clutch size. In the field-collected clusters many clusters were female-biased but some clusters (3.8%) produced only male wasps, suggesting that there is a low percentage of unmated females in the field. Superparasitism was common in the field, and females were believed to increase progeny sex ratio when attacking previously parasitized hosts. In the laboratory, the number of eggs laid in a day tended to decrease with increasing female age. For females that were offered two hosts per day and for those offered three hosts per day, this value became nearly the same at 9 days after the start of oviposition. Old females which attacked many hosts tended to lay fewer eggs in a day than young ones. However, the degree of this tendency was not the same for all the parasitoid females of all three groups because sperm remained viable throughout a female’s lifetime. The amount of sperm used in a single oviposition bout seemed fixed and was not dependent on the number of eggs laid. Over the 2 days of the clutch size response experiment, the number of hosts a female attacked per day was not affected by the presence or absence of honey.     

Effect of different cole crops on the biological parameters of <Emphasis Type="Italic">Pieris brassicae</Emphasis> (L.) (Lepidoptera: Pieridae) under laboratory conditions

The effect of different cole crops was studied on biological parameters of Pieris brassicae (L.) in the laboratory at 28 °C, 65% RH, and 12L:12D photoperiod. The results indicated that host plants significantly affected the life history, i.e. survival of developmental stages, oviposition period, and sex ratio of P. brassicae. Comparative study on different host plant revealed that P. brassicae required a maximum of 40 days to complete generation on cabbage, cauliflower, and broccoli. The survivorship and expectation of life declined gradually with the advancement of age; the life expectancy of newly deposited eggs was 23.96 days while it was 8.12 days at the time of adult emergence on cabbage. However, the fluctuations of mortality parameter were seen on all the cole crops. On cabbage, 100% hatching of eggs with low larval mortality were noticed. The highest net reproductive rate (R₀) occurred on cauliflower, i.e. 27.1 followed by cabbage 24.89, females per female per generation. Intrinsic rate of increase (r_m), was found to be highest (0.09558954) on cauliflower followed by broccoli and cabbage, 0.078886 and 0.077551 females per female per day, respectively. The smallest r_m (0.059469 females per female per day) occurred on radish which shows that P. brassicae did not perform well on radish. In addition, P. brassicae may double in 7.2 days on cauliflower, 8.7 days on broccoli, and 8.9 days on cabbage. The sex ratio was computed as 1.5:1, female:male, respectively on cabbage.     

Effects of arbuscular mycorrhizal fungi on the growth of two turfgrasses grown under greenhouse conditions

ABSTRACT

The need for salinity resistance in turfgrass is increasing because of the enhanced use of effluent and other low-quality water for turfgrass irrigation. Although most turfgrasses form an arbuscular mycorrhizal fungus (AMF) symbiosis, there is little information on the mycorrhization of turfgrass species. Therefore, the aim of this study was to determine the effects of three AMF species, Glomus intraradices Schenck & Smith, Glomus etunicatum Becker & Gerdemann, and Glomus deserticola Trappe & John, and a mixture thereof on the growth, productivity, and nutrient uptake of two species of cool-season turfgrasses, Challenger Kentucky bluegrass (Poa pratensis L.) and Arid tall fescue (Festuca arundinacea Schreb.), and to relate the effects to colonization of the roots by mycorrhiza to assess the dependency of the plants (mycorrhizal dependency [MD]). Following the experimental period (4 months) and measurements, the mycorrhizal inoculated plants had significantly greater biomass production compared to that of non-inoculated plants. MD and shoot mineral contents (particularly P) differed among turfgrass hosting AMF, and the highest value (13%) occurred for P. pratensis and F. arundinacea seedlings colonized with G. intraradices and G. deserticola, respectively. The P content was highest for the F. arundinacea/mixed AMF combination compared to other treatments. We confirmed that mycorrhizal inoculation (P. pratensis/G. intraradices and F. arundinacea/mixed AMF combinations) enhanced plant productivity and nutrient uptake (especially P) even under non-optimum conditions.     

Phosphorous and beneficial microorganism influence yield and yield components of wheat under full and limited irrigated conditions

Field experiment was conducted to investigate the impact of phosphorus (P) and beneficial microorganism (BM) on the yield and yield components wheat (Triticum aestivum L., cv. Siren-2010). The experiment was conducted under full (five irrigations) and limited (two) irrigation conditions at the Research Farm of The University of Agriculture Peshawar during winter 2012–13. The experiment under both full and limited irrigated conditions was laid out in randomized complete block design using three replications. The results showed that irrigated plots produced more spikes m^?2 (254), grains spike^?1 (55.5), heavier thousand grains weight (39.4 g), and higher grain yield (3612 kg ha^?1 than limited irrigated condition. Application of P at the highest rate (90 kg P ha^?1) produced more spikes m^?2 (260) and grains spike^?1 (52.4), and increased maximum thousand grain weight (39.1 g) and grain yield (3617 kg ha^?1). Application of BM at the highest rate (30 L ha^?1) resulted in maximum number of spikes m^?2 (257) and grains spike^?1(51.7), highest thousand grains weight (39.1 g) and grain yield (3765 kg ha^?1). The results confirmed that under full irrigated condition the increase in both P and BM levels (90 kg P ha^?1 and 30 L ha^?1, respectively) and under limited irrigated condition the intermediate levels of both P and BM (60 kg P ha^?1 and 20 L ha^?1, respectively) could increase wheat productivity under semi-arid conditions.