Rice allelopathy in weed management : an integrated approach

The intensive use of pesticides with low biodegradability and high persistence in soil, surface and ground waters, represents a considerable environmental risk, especially under high weed pressure conditions. Furthermore, the number of herbicide-resistant weeds is increasing. Against this background, the investigation of alternative weed control strategies has taken on considerable importance. Among these, allelopathy as a negative effect of one plant on another due to the direct or indirect (including microorganisms) release of chemicals in the environment can be a useful tool for the integrated management of weeds in agroecosystems. In particular, the paddies have been considered in this work by reviewing the data both on rice allelopathy and rice weed agronomic control methods developed to improve the crop yield

Elicitation of the allelopathic potential of rice by methyl salicylate treatment

Weed infestation is one of the most severe problems affecting rice production worldwide. Current weed control practices are either costly or pose a threat to the environment. The use of competitive rice genotypes seems to be a promising strategy. The aim of our study was to improve the allelopathic potential of three selected rice genotypes by foliar application of methyl salicylate (MeSA), a signaling molecule eliciting the plant defense response. Aqueous extracts of the shoots and roots of two competitive (UPR 2962-6-2-1 and Govind) and one non-competitive (UPR 2992-17-3-1) rice genotypes treated with MeSA solution at different concentrations (1 mM, 2 mM, and 3 mM) showed phytotoxic effects on the growth of the weed Echinochloa colona. Specifically, shoot and root extracts obtained from the competitive rice genotypes similarly decreased both the E. colona germination rate (9% to 44.5%) and the length of its roots and shoots (11% to 48%). Extracts of the non-competitive rice genotype showed a similar trend but lower effects, inhibiting the E. colona germination up to 32% and reducing the growth of the weed roots and shoots by 6-23.5% and 7-28%, respectively, according to the increasing MeSA concentrations. High-performance liquid chromatography (HPLC) analysis demonstrated an increase in different allelopathic phenolic acids in the three rice genotypes in response to MeSA treatments. Among the detected compounds, vanillic and protocatechuic acids showed the greatest differences compared to controls with values up to 2.1-fold higher in shoots of the two competitive UPR-2962-6-2-1 and Govind rice genotypes, while their roots were characterized by the greatest increases of 8-hydroxyquinoline (8.2-fold) and protocatechuic acid (1.7-fold). Differently, non-competitive genotype UPR 2992-17-3-1 showed the highest increase for gallic acid (2.2-fold) in shoots and for p-hydroxybenzoic acid (2.4-fold) in roots. Lastly, MeSA was found to improve the competitiveness of rice genotypes without any detrimental effect on the host plant

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Not AvailableHerbicidal effects of leaf oil from 3-Eucalyptus species (Eucalyptus citriodora, Eucalyptus camaldulensis and Eucalyptus tereticornis) were evaluated on germination and seedlings growth of Parthenium hysterophorus L. In laboratory bioassay the different concentrations of eucalyptus essential oils significantly reduced the seed germination. Based on the germination, a dose-response curve was made and LC25 values were calculated as 0.35, 0.8 and 1.8 mg/L for E. citriodora, E. camaldulensis and E. tereticornis, respectively. The E. citriodora proved most inhibitory to seedling growth and biomass of P. hysterophorous, even at 0.25 mg/L. Spraying of E. citriodora on P. hysterophorous 4-wk-old plants decreased the plants height, membrane integrity and cellular defense i.e. showed the adverse effects of eucalyptus leaf essential oil on growth, photosynthesis and energy metabolism of target plants. Exposure of P. hysterophorus to E. citriodora leaf essential oil also enhanced the electrolyte leakage, indicating membrane disintegration. An increased level of H2O2 in spray treatment indicates the induction of oxidative stress. Thus the essential oil from E. citriodora inhibited the P. hysterophorus growth through oxidative damage, hence, could be used as directed spray to control P. hysterophorus. Key words: Electrolyte leakage, essential oil, Eucalyptus camaldulensis, Eucalyptus citriodora, Eucalyptus tereticornis, germination, hydrogen peroxide, inhibition, Parthenium hysterophorus, phytotoxicity, seedlings growthNot Availabl

RE-LOOK IN TO UPGRADING OF DIESEL FUELS BY AROMATICS SATURATION

Increasing environmental awareness is compelling the statutory bodies to make the fuel specifications more and more stringent. Meeting these dynamic specifications, particularly with respect to aromatics and sulphur, is one of the major challenges faced by the refiners. Although at present no well defined regulations about aromatics content in diesel fuel exists in European and Indian specifications, their presence is indirectly regulated by Cetane index, Cetane number and PAH specifications. For meeting these specifications the current trend is to use hydro processing technologies for desulphurisation and dearomatisation. Amongst these two, it is well established that reducing the aromatics through hydrogenation is a much tougher job than hydrodesulphurization as it requires high pressure operation and high hydrogen consumption particularly for high aromatic feed stocks. This not only results in increasing the capital and operating cost but also leads to formation of more Green House gases. Thus to meet future fuel specifications, significant capital investments are needed. On the contrary refinery margins are going down day by day posing a real challenge. In particular, small and medium size petroleum refiners will have to confront the need for a hydrogen plant, hydro treating unit, and a sulphur plant. In view of these reasons, attempts are being made world wide to evaluate alternative options to hydro processing technologies. Commercial processes by using other options e.g. adsorption, oxidation followed by extraction are already available to produce ultra low sulphur ( S< 50 ppm) middle distillates however, no such options are available for de-aromatisation. Indian Institute of Petroleum (IIP) has recently developed NMP extraction process for the dearomatisation of middle distillates. This process uses novel re-extraction route instead of conventional energy intensive distillation route for the recovery of hydrocarbons. The advantages of this technology over hydro treatment are requirement of low capital costs and production of valuable aromatic extract as by product. Experimental data were generated with model hydrocarbons and actual feedstock for extraction and re-extraction steps. UNIFAC group contribution approach was used to predict the LLE data and simulate continuous extraction runs. Process flow sheet was conceptualized and simulated on ASPEN PLUS simulator and utilities were estimated for optimum operating conditions. This paper presents the details of various steps involved in the technology development for de-aromatisation of middle distillate through re-extraction. Case studies comparing the preliminary economics of hydro dearomatisation vis a vis NMP extraction technology for up-gradation of middle distillates are also presented

Ethylene mediated physiological response for in vitro development of salinity tolerant tomato

Tomato is an important crop and has immense health benefits and medicinal value. Here, we described how salinity stress affects tomato plant growth and developmental processes and productivity. It causes ionic toxicity, oxidative damage, osmotic stress, and hormonal imbalance. In this review, we emphasized the crucial role of ethylene (ET) towards in vitro development of tomato crop by mediating stress response, particularly high salt. There are evidences that salinity stress modulates the expression of ACS and beta-CAS, which leads to ET and cyanide accumulation. We draw attention to how ET negatively or positively mediates salinity stress response by maintaining endogenous biomolecules, Na+/K+ ion balance and redox homeostasis. How ET inhibitors and polyamines as protectants reverse the negative effects of ET/salinity stress-induced cellular damage by cross talk with important physiological processes-photosynthesis and respiratory and salt overly sensitive (SOS). The literature appraised herein will contribute to a better understanding of the development of salinity stress tolerant tomato