Phytotoxic effects of Parthenium hysterophorus residues on three Brassica species

A study was conducted to assess the phytotoxicity of residues of Parthenium hysterophorus , an exotic invasive weed, towards the growth of three Brassica species ( Brassica campestris, Brassica oleracea and Brassica rapa ). The early growth of crops, measured in terms of seedling length and dry weight, was significantly reduced when grown in soil amended with varying amounts of Parthenium residues. A direct relationship was observed between the amount of residue incorporated in the soil and growth reduction. This adverse effect on Brassica crops indicates the presence of some growth-retardatory substances which are possibly released by the residues into the soil medium. In order to test this, aqueous extracts (1, 2, and 4%) of residues were prepared. It was observed that, in a laboratory bioassay, these extracts severely reduced the early growth of Brassica species, thereby indicating the presence of some water-soluble, inhibitory principles in Parthenium residues. A significant amount of the phenolics, the largest group of secondary metabolites usually implicated in allelopathy, was estimated in residue extracts, as well as in residue-incorporated soil. The phenolic content increased with increasing residue concentration, thereby showing their direct involvement in the observed growth inhibitions. Therefore, the study establishes that Parthenium residues exert an allelopathic influence on the early growth of Brassica crops by releasing water-soluble phenolics into the soil.     

Precision phenotyping of contrasting potato(Solanum tuberosum L.) varieties in a novel aeroponics system for improving nitrogen use efficiency: In search of key traits and genes

With increasing population, degrading soil health, limited arable land area, and high cost of nitrogen(N) fertilizers, improving nitrogen use efficiency(NUE) of potato is an inevitable approach to save the environment and achieve sufficient tuber yields with less N fertilizer supply. Recently, we have developed an aeroponics system to study NUE in potato using genomics, physiology, and breeding approaches. This study aims on precision phenotyping of plants of two distinct potato varieties(Kufri Gaurav, N efficient; Kufri Jyoti, N inefficient) in the novel aeroponics system. Plants were grown in aeroponics under controlled conditions with low N(0.75 mmol L~(-1) NO_3~-) and high N(7.5 mmol L~(–1) NO_3~-) levels. Plant biomass, root traits, total chlorophyll content, and plant N were increased with increasing N supply, whereas higher NUE parameters namely NUE, agronomic NUE(Ag NUE), N uptake efficiency(NUp E), harvest index(HI), and N harvest index(NHI) were observed at low N. An NUE efficient cv. Kufri Gaurav showed higher tuber dry weight, fresh tuber yield, tuber number per plant, early start of tuber harvesting, root traits, stolon traits, NUE parameters, and higher amino acid(aspartic acid and asparagine) content at low N supply. Higher expression of nitrate reductase(NR), nitrite reductase(NIR), and asparagine synthetase(AS) genes was observed in the leaf tissues of Kufri Gaurav at high N. Thus, aeroponics-based precision phenotyping enables identification of NUE efficient genotypes based on key traits and genes involved in improving NUE in potato. Further, this study suggests that the potential of aeroponics can be utilized to investigate N biology in potato under different N regimes.     

Changes with time in the potassium content and phyllosilicates in the soil of the Broadbalk continuous wheat experiment at Rothamsted

The transformations of phyllosilicates and the changes in potassium (K) balances caused by long-term cropping have been examined in soil from the 153-year-old Broadbalk experiment. Samples taken between 1856 and 1987 and kept in archive were fractionated for particle size and analysed for changes in mineralogy by X-ray diffraction and changes in total K of the coarser and fine fractions. These were compared with K balances made from records of cropping and fertilizer application. No change in mica due to cropping and K-depletion could be detected. Deep ploughing after 1925 mixed chlorite from the subsoil into the surface soil, but this had weathered by 1987. Potassium balances did not agree with measured changes in total K presumably because of unquantified uptake of K from the subsoil and poorly quantified K leaching.     

Genetic variability for seed oil content and seed index in some wild species and perennial races of cotton

A 3‐year study was made on genetic variability of seed oil content and seed index with 20 wild species, two cultivated species and six perennial races of Gossypium arboreum cotton maintained at the Central Institute for Cotton Research, Nagpur, India. The mean seed oil content varied from 10.26 to 22.89% in 22 species of Gossypium and six races of G. arboreum. In this material the weight of delinted seed varied from 43.33 to 54.54 mg/seed. The highest seed oil content was recorded in the species G. lobatum followed by G. harknessii. On average, for both traits, the means were higher for G. arboreum and its races. However, G. africanum and G. harknessii reached the level of G. arboreum and its races for seed weight, while five wild species surpassed the best races and G. arboreum in seed oil content, among them was G. harknessii. To breed simultaneously for seed oil content and seed weight, crosses between races of G. arboreum and wild species of Gossypium seem to be promising.     

Effect of pH-shifting on the gel forming characteristics of salt-ground meat from walleye pollack

ABSTRACT:   In order to elucidate the mechanism of the changes in gel forming characteristics of fish meat by pH-lowering, the gelation-temperature curve and the gelation-moisture content curve were examined using the acidified walleye pollack surimi or neutralized one after acidification. In the gelation-temperature curve, the gel strength was highest at 30°C and lowest at approximately 50–60°C, irrespective of pH shifting. The gel strength at 30°C and 80°C decreased with the decrease in pH value. The neutralization of acidified surimi improved the gel strength, but it was considerably lower than the original gel strength. The gel strength at 50–60°C was not affected by pH lowering. The gel strength at 80°C could not be revived to the original by pH readjustment, either in the presence or in the absence of EDTA. These results suggest that irreversible changes of meat protein take place under the low pH, and the oxidation ability of sulfhydryl (SH) groups of protein molecule is not affected by pH-shifting.     

Leaf Construction Cost and Related Ecophysiological Parameters of Rice Crop and Its Important Weeds

To understand the reason for the success of weeds,we investigated the energetic cost of leaf construction,and certain ecophysiological traits of rice and its dominant weeds.On physiological basis among all weeds,Caesulia axillaris Roxburgh was found to be the most serious,followed by Echinochloa cruss-galli L.Beauv and Echinochloa colonum L.Link,while Fimbristylis miliaceae L.Vahl and Cyperus iria L.were moderate weeds of the rice fields.C.axillaris had the lowest leaf construction cost (LCC) both on a mass basis (1.15 g/g) and on a unit area basis (22.93 g/m2).Comparatively higher specific leaf area,photosynthetic rate,photosynthetic nitrogen use efficiency,leaf area ratio and leaf area index provided C.axillaris with further competitive advantage.Low LCC suggests that weeds utilize carbon resource more efficiently than the crop and potentially spend the saved energy on other competitive strategies viz.seed production,biomass production and high relative growth rate,which results in low crop yield and increase in weed seed bank.     

Micronutrient enrichment mediated by plant-microbe interactions and rice cultivation practices

A field experiment was conducted to evaluate the effect of different plant growth promoting microorganisms (PGPM) on micronutrient enrichment of rice crops grown under conventional (flooded) and SRI (System of Rice Intensification) practices. Significant differences were recorded among treatments and cultivation practices in terms of soil microbial activity reflected in enhanced nutrient uptake, enzyme activity, and yield. The Anabaena-based biofilm inoculants were particularly superior under both methods of cultivation, leading to 13–46% enhancement of iron and 15-41% enhancement of zinc in rice grains over uninoculated controls. SRI was found to be superior in terms of enhancing the concentration of zinc, copper, iron, and manganese (Zn, Cu, Fe and Mn), particularly in grains, and significant in increasing the activity of defense- and pathogenesis- related enzymes and yield parameters. This study illustrates the utility of cyanobacteria-based inoculants for both methods of rice cultivation and their significant interactions with the plant, leading to micronutrient enrichment of rice grains. Such formulations can complement the current biofortification strategies and help in combating the problems of malnutrition globally.     

除草剂和土壤改良剂对热带农业生态系统中微生物生物量动态的影响

The influences of herbicide alone and in combination with the soil amendments with contrasting resource qualities on dynamics of soil microbial biomass C (MBC), N (MBN), and P (MBP) were studied through two annual cycles in rice-wheat-summer fallow crop sequence in a tropical dryland agroecosystem. The experiment included application of herbicide (butachlor) alone or in combination with various soil amendments having equivalent amount of N in the forms of chemical fertilizer, wheat straw, Sesbania aculeata, and farm yard manure (FYM). Soil microbial biomass showed distinct temporal variations in both crop cycles, decreased from vegetative to grain-forming stage, and then increased to maximum at crop maturity stage. Soil MBC was the highest in herbicide + Sesbania aculeata treatment followed by herbicide + FYM, herbicide + wheat straw, herbicide + chemical fertilizer, and herbicide alone treatments in decreasing order during the rice-growing period. During wheat-growing period and summer fallow, soil MBC attained maximum for herbicide + wheat straw treatment whereas herbicide + FYM, herbicide + Sesbania, and herbicide + chemical fertilizer treatments showed similar levels. The overall trend of soil MBN was similar to those of soil MBC and MBP except that soil MBN was higher in herbicide + chemical fertilizer treatment over the herbicide + wheat straw treatment during rice-growing period. In spite of the addition of equivalent amount of N through exogenous soil amendments in combination with the herbicide, soil microbial biomass responded differentially to the treatments. The resource quality of the amendments had more pronounced impact on the dynamics of soil microbial biomass, which may have implications for long-term sustainability of rainfed agroecosystems in dry tropics.     

利用土壤传递函数估算土壤水力学特性研究进展

Characterization of soil hydraulic properties is important to environment management; however, it is well recognized that it is laborious, time-consuming and expensive to directly measure soil hydraulic properties. This paper reviews the development of pedotransfer functions (PTFs) used as an alternative tool to estimate soil hydraulic properties during the last two decades. Modern soil survey techniques like satellite imagery/remote sensing has been used in developing PTFs. Compared to mechanistic approaches, empirical relationships between physical properties and hydraulic properties have received wide preference for predicting soil hydraulic properties. Many PTFs based on different parametric functions can be found in the literature. A number of researchers have pursued a universal function that can describe water retention characteristics of all types of soils, but no single function can be termed generic though van Genuchten (VG) function has been the most widely adopted. Most of the reported parametric PTFs focus on estimation of VG parameters to obtain water retention curve (WRC). A number of physical, morphological and chemical properties have been used as predictor variables in PTFs. Conventionally, regression algorithms/techniques (statistical/neural regression) have been used for calibrating PTFs. However, there are reports of utilizing data mining techniques, e.g., pattern recognition and genetic algorithm. It is inferred that it is critical to refine the data used for calibration to improve the accuracy and reliability of the PTFs. Many statistical indices, including root mean square error (RMSE), index of agreement (d), maximum absolute error (ME), mean absolute error (MAE), coefficient of determination (r²) and correlation coefficient (r), have been used by different researchers to evaluate and validate PTFs. It is argued that being location specific, research interest in PTFs will continue till generic PTFs are developed and validated. In future studies, improved methods will be required to extract information from the existing database.