A bacteriological study of the natural flora of edible oyster, Crassostrea madrasensis

The total viable bacterial populations in the oysters and the sea water from the edible oyster farm at Tuticorin were in the range of 10 super(3) to 10 super(4) per ml and 1 super(2) to 10 super(3) per ml respectively. The maximum most probable number of faecal coliform recorded during the one year period of study of both the oysters and seawater were 33 per 100 ml. Pathogenic bacteria (Salmonella sp., Vibrio cholerae, coagulase positive staphylococci and faecal streptococci were absent in oysters and farm water. Study of 197 (98 taken from oyster liquid and 99 from oyster farm water) randomly isolated cultures indicated that gram negative asporogenus rod-like bacteria of the Vibrio, Flavobacterium, Achromobacter and Pseudomonas groups were the dominant flora of the oyster liquid as well as seawater

Correlation and R2 analysis of radicle emergence test to predict seed vigour and field emergence in blackgram (Vigna mungo L.) seed lots

Blackgram (Vigna mungo L.) is one of the major pulse crops grown throughout India.  Prediction of seed vigour and field emergence of seed before sowing is important for assured yield. A standard germination test is time-consuming and does not always show the seed lot potential performance, especially if field conditions are not optimal. There is need of advanced technology, which can give a precise result in a short period. The experiment was conducted to correlate the radicle emergence test with seed vigour parameters to predict seed vigour and planting value of 10 varying vigour lots (L1, L2, L3, L4 - high vigour lots; L5, L6, L7 - medium vigour lots; L8, L9, L10 - low vigour lots) of blackgram var. VBN 6. The study showed that all the seed vigour parameters of the blackgram were more highly correlated with the percentage of radicle emergence with 2 mm length than with 1 mm length. The correlation analysis results showed that the radicle emergence test with 2 mm radicle length at 28 hours had a highly significant negative correlation with EC (electrical conductivity) of seed leachate (-0.974**), followed by MJGT (mean just germination time) (-0.967**) and MGT (mean germination time) (-0.933**). However, it was positively correlated with field emergence (0.972**), germination (0.952**) and dehydrogenase enzyme activity (0.928**). The maximum R2 value of 0.923 was recorded in the 28-hour counting of radicle emergence with a length of 2 mm compared with the 26-hour counting of radicle emergence with a length of 1 mm (0.913). The study concluded that counting 2 mm radicle emergence at the 28th hour could be used to quickly evaluate seed vigour in field emergence in blackgram seed lots

Radicle emergence test as a quick vigour test to predict field emergence performance in rice (Oryza sativa L.) seed lots

An experiment was made to standardize the radicle emergence test to predict the field emergence performance in ten different seed lots [L1 to L4: high vigour lots (> 90 % germination), L5 to L7: medium vigour lots (80-90 % germination) and L8 to L10: low vigour lots (< 80 % germination)] of rice cv. CO 51. The results showed that the significant differences are observed in physiological and biochemical parameters in different seed lots. The seed vigour was classified into three groups viz., high, medium and low vigour based on the relationship between mean germination time and field emergence. When the Mean Germination Time (MGT) was < 34 hours, the field emergence was > 85 per cent, which was considered as high vigour; when the MGT was 34-35 hours, the field emergence was 80-85 per cent, that was considered as medium vigour; when the MGT was > 35 hours, the field emergence was < 80 per cent, that was considered as low vigour. The radicle emergence test (2mm radicle length) was highly negatively correlated with mean germination time (-0.930**) followed by mean just germination time (-0.852**) and electrical conductivity of seed leachate (-0.827**) and it was positively correlated with field emergence (0.894**) followed by germination (0.878**) and dehydrogenase activity (0.864**). The R2 values between seed vigour parameters and radicle emergence test were significantly higher in 2mm length of radicle emergence when compared with 1mm length of radicle emergence. Finally, the study concluded that 36 hour MGT with the attainment of 2mm radicle emergence percentage could be used as a quick method to assess rice seed lots' quality by the seed analysts and seed industry

Impact of different levels of iron on mitigation of iron chlorosis in varagu CO 3 (Paspalum scrobiculatum. L)

Iron (Fe) deficiency is a major nutritional disorder in crops growing in calcareous soils. Varagu crop are more susceptible to (Fe) deficiency in the early stage of growth and the deficiency is exhibited as chlorosis developing interveinally in the new leaves.  The objective of the present study was to see the impact of different levels iron on mitigation of chlorosis in varagu, Paspalum scrobiculatum under calcareous soil and to investigate the influence of soil and foliar application of iron on growth, physiological and improvement of yield potential of varagu under calcareous soil condition. The varagu variety CO3 taken for this study The treatments comprised T1, NPK (44:22:0 kg ha-1) + 12.5 t  FYM/ha,T2, NPK (44:22:30 kg ha-1) +12.5 t FYM/ha, T3, T1 + Soil application of FeSO4   (25 kg ha-1), T4, T2 + Soil application of FeSO4 (25 kg ha-1), T5, T1 + Soil application of FeSO4 (50 kg ha-1), T6, T2 + Soil application of FeSO4 (50 kg ha-1), T7, T3 + Foliar spray of 0.5% FeSO4, T8, T4 + Foliar spray of 0.5% FeSO4, T9,T5 + Foliar spray of 0.5% FeSO4, T10,  T6 + Foliar spray of 0.5% FeSO4. During experimentation, morphological characteristics, growth attributes, physiological and biochemical components and biomass traits determined the mitigation of iron chlorosis. The iron deficiency in varagu was effectively controlled by T10, soil treatment 50 kg ha-1 FeSO4 and foliar spray of 0.5% FeSO4 applied on the 30th and 50th days after sowing through maintaining highest growth parameter values, maximum catalase and peroxidase activity and maintaining more chlorophyll content

Genetic diversity and population structure of leaf-nosed bat Hipposideros speoris (Chiroptera: Hipposideridae) in Indian subcontinent

Genetic variation and population structure of the leaf-nosed bat Hipposideros speoris were estimated using 16S rRNA sequence and microsatellite analysis. Twenty seven distinct mitochondrial haplotypes were identified from 186 individuals, sampled from eleven populations. FST test revealed significant variations between populations in the overall pairwise estimation (FST = 0.710; p < 0.001). In addition, haplotype network and analysis of molecular variation analysis (AMOVA) consistently suggest the prevalence of genetic structure in the sampled populations. However, the mtDNA data was not significantly different in few closely located urban populations, but significant difference has been observed with the use of microsatellite data. The Bayesian clustering analysis identified eight clusters among the populations; the clustering pattern also corresponded to the haplotype networks. Overall, the present study suggests a “macrogeographic genetic isolation-by-distance” and possibility of gene flow among closely located populations.Key words: mtDNA, 16S rRNA, microsatellite, population structure, Hipposideros speoris

Cationic exchange in nanosized ZnFe2O4 spinel revealed by experimental and simulated near-edge absorption structure

The non-equilibrium cation site occupancy in nanosized zinc ferrites (6-13 nm) with different degree of inversion (0.2 to 0.4) was investigated using Fe and Zn K-edge x-ray absorption spectroscopy XANES and EXAFS, and magnetic measurements. The very good agreement between experimental and ab-initio calculations on the Zn K-edge XANES region clearly show the large Zn2+(A)--Zn2+[B] transference that takes place in addition to the well-identified Fe3+[B]--Fe3+(A) one, without altering the long-range structural order. XANES spectra features as a function of the spinel inversion were shown to depend on the configuration of the ligand shells surrounding the absorbing atom. This XANES approach provides a direct way to sense cationic inversion in these spinel compounds. We also demonstrated that a mechanical crystallization takes place on nanocrystalline spinel that causes an increase of both grain and magnetic sizes and, simultaneously, generates a significant augment of the inversion.Comment: 5 pages, 5 eps figures, uses revtex4, corrected table

Crystallographically oriented magnetic ZnFe2O4 nanoparticles synthesized by Fe implantation into ZnO

In this paper, a correlation between structural and magnetic properties of Fe implanted ZnO is presented. High fluence Fe^+ implantation into ZnO leads to the formation of superparamagnetic alpha-Fe nanoparticles. High vacuum annealing at 823 K results in the growth of alpha-Fe particles, but the annealing at 1073 K oxidized the majority of the Fe nanoparticles. After a long term annealing at 1073 K, crystallographically oriented ZnFe2O4 nanoparticles were formed inside ZnO with the orientation relationship of ZnFe2O4(111)[110]//ZnO(0001)[1120]. These ZnFe2O4 nanoparticles show a hysteretic behavior upon magnetization reversal at 5 K.Comment: 21 pages, 7 figures, accepted by J. Phys. D: Appl. Phy

Magnetic enhancement of Co0.2_{0.2}Zn0.8_{0.8}Fe2_2O4_4 spinel oxide by mechanical milling

We report the magnetic properties of mechanically milled Co$_{0.2}$Zn$_{0.8}$Fe$_2$O$_4$ spinel oxide. After 24 hours milling of the bulk sample, the XRD spectra show nanostructure with average particle size $\approx$ 20 nm. The as milled sample shows an enhancement in magnetization and ordering temperature compared to the bulk sample. If the as milled sample is annealed at different temperatures for the same duration, recrystallization process occurs and approaches to the bulk structure on increasing the annealing temperatures. The magnetization of the annealed samples first increases and then decreases. At higher annealing temperature ($\sim$ 1000$^{0}$C) the system shows two coexisting magnetic phases {\it i.e.}, spin glass state and ferrimagnetic state, similar to the as prepared bulk sample. The room temperature M\"{o}ssbauer spectra of the as milled sample, annealed at 300$^{0}$C for different durations (upto 575 hours), suggest that the observed change in magnetic behaviour is strongly related with cations redistribution between tetrahedral (A) and octahedral (O) sites in the spinel structure. Apart from the cation redistribution, we suggest that the enhancement of magnetization and ordering temperature is related with the reduction of B site spin canting and increase of strain induced anisotropic energy during mechanical milling.Comment: 14 pages LaTeX, 10 ps figure

Aquaporins and their implications on seeds: A brief review

Aquaporins (AQPs) are water channel proteins. They play a key role in maintaining water balance and homeostasis in cells under stress conditions in living organisms. AQPs are pore forming transmembrane proteins that facilitate water movement and various small neutral solutes across cellular membranes. Aquaporin expression and transport functions are modulated by various phytohormones mediated signalling in plants. Transcriptome analysis revealed the role of aquaporins in regulating hydraulic conductance in plant roots and leaves. Different AQPs found in the seed system have individual functions that are more time and tissue specific, ultimately helping in the seed imbibition process to complete seed germination. Seed specific TIP3s aquaporin helps to maintain seed longevity under expressional control of ABI3 during seed maturation and heat shock proteins and late embryogenic abundant proteins. Under stress circumstances, the major significance of aquaporin expression in seeds is to maintain water influx and efflux rates, as well as protein modification, post translational alterations, nutritional acquisition and allocation, subcellular trafficking and CO2 transport. The present review mainly focused on aquaporin structure, classification, role and functional activity during solute transport, reproductive organs development, plant growth development, abiotic stress response and also various roles in seeds such as seed biology, seed development and maturation, seed dormancy, seed germination and longevity