The demand for energy around the world is increasing, specifically the demand for petroleum-based energy. Appeasing this growing energy demand without irreparably damaging the environment is of primary concern. With rising fuel prices and environmental concerns, alternative fuels could satisfy the need for renewable energy with low environmental impact. Some of the more popular alternative fuels for new vehicles are ethanol, hydrogen, and biodiesel. Although gasoline engines are expected to be replaced by hydrogen-powered fuel cells, compression-ignition engines, the diesel engines, are expected to remain in use for high-power applications because of limitations of hydrogen-storage densities. The viable environmental friendly alternative fuel for compression-ignition engines is methyl esters (commonly known as biodiesel), which is derived from vegetable oils or animal fats. Using biodiesel instead of conventional diesel fuel reduces emissions such as the overall life cycle of carbon dioxide (CO2), particulate matter, carbon monoxide, sulfur oxides (SOx), volatile organic compounds (VOCs), and unburned hydrocarbons significantly. However, biodiesel increases nitrogen oxides (NO x ) emissions, mostly NO and NO2, which are considered as zone A hazardous compounds. This paper reviews the kinetics of NO x formation in relation to thermal, prompt, and fuel NO x formation processes and critically reviews the techniques that have been attempted to reduce NO x emissions from mechanisms to effectively reduce the NO x formation with biodiesel fuel.

Arabidopsis PP2C belonging to group A have been extensively worked out and known to negatively regulate ABA signaling. However, rice (Oryza sativa) orthologs of Arabidopsis group A PP2C are scarcely characterized functionally. We have identified a group A PP2C from rice (OsPP108), which is highly inducible under ABA, salt and drought stresses and localized predominantly in the nucleus. Genetic analysis revealed that Arabidopsis plants overexpressing OsPP108 are highly insensitive to ABA and tolerant to high salt and mannitol stresses during seed germination, root growth and overall seedling growth. At adult stage, OsPP108 overexpression leads to high tolerance to salt, mannitol and drought stresses with far better physiological parameters such as water loss, fresh weight, chlorophyll content and photosynthetic potential (Fv/Fm) in transgenic Arabidopsis plants. Expression profile of various stress marker genes in OsPP108 overexpressing plants revealed interplay of ABA dependent and independent pathway for abiotic stress tolerance. Overall, this study has identified a potential rice group A PP2C, which regulates ABA signaling negatively and abiotic stress signaling positively. Transgenic rice plants overexpressing this gene might provide an answer to the problem of low crop yield and productivity during adverse environmental conditions.

Ca2+ homeostasis is required to maintain a delicate balance of cytosolic Ca2+ during normal and adverse growth conditions. Various Ca2+ transporters actively participate to maintain this delicate balance especially during abiotic stresses and developmental events in plants. In this study, we present a genome‐wide account, detailing expression profiles, subcellular localization and functional analysis of rice Ca2+ transport elements. Exhaustive in silico data mining and analysis resulted in the identification of 81 Ca2+ transport element genes, which belong to various groups such as Ca2+‐ATPases (pumps), exchangers, channels, glutamate receptor homologs and annexins. Phylogenetic analysis revealed that different Ca2+ transporters are evolutionarily conserved across different plant species. Comprehensive expression analysis by gene chip microarray and quantitative RT‐PCR revealed that a substantial proportion of Ca2+ transporter genes were expressed differentially under abiotic stresses (salt, cold and drought) and reproductive developmental stages (panicle and seed) in rice. These findings suggest a possible role of rice Ca2+ transporters in abiotic stress and development triggered signaling pathways. Subcellular localization of Ca2+ transporters from different groups in Nicotiana benthamiana revealed their variable localization to different compartments, which could be their possible sites of action. Complementation of Ca2+ transport activity of K616 yeast mutant by Ca2+‐ATPase OsACA7 and involvement in salt tolerance verified its functional behavior. This study will encourage detailed characterization of potential candidate Ca2+ transporters for their functional role in planta.

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