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Increasing use of nanoparticles in daily products is of great concern today, especially when their positive and negative impact on environment is not known. Hence, in current research, we have studied the impact of silver nanoparticle (AgNPs) and silver nitrate (AgNO3) application on seed germination, root, and shoot length of castor bean, Ricinus communis L. plant. Silver nanoparticles had no significant effects on seedling growth even at higher concentration of 4,000 mg L(-1), while the silver in bulk form as AgNO3 applied on the castor bean seeds inhibited the seed germination. Silver uptake in seedlings of the castor seeds on treatment with both the forms of silver was confirmed through atomic absorption spectroscopy studies. The silver nanoparticle and silver nitrate application to castor seeds also caused an enhanced enzymatic activity of ROS enzymes and phenolic content in castor seedlings. High-performance liquid chromatography analysis of individual phenols indicated enhanced content of parahydroxy benzoic acid. These kinds of studies are of great interest in order to unveil the movement and accumulation of nanoparticles in plant tissues for assessing future applications in the field or laboratory.

A laboratory study was undertaken to ascertain the impact and the extent of feeding by different pests on biochemical constituents and various enzyme levels in rice plants. The difference in these parameters due to the pest damage by three different modes of feeding was also studied and compared. The borer pest-yellow stem borer (YSB), Scirpophaga incertulas (W); surface feeder--leaf roller (LR), Cnaphalocrosis medinalis (G) and a sucking pest-brown plant hopper (BPH), Nilaparvata lugens (S) fed rice plants were analyzed for the quantitative and qualitative changes in biochemical profile and enzymatic changes that occur as plant's defensive responses were analyzed spectrophotometrically. The phenolic acids were analyzed using HPLC and quantitated with the standard samples. The quantity of biochemicals such as proteins, phenols and carbohydrates has been enhanced along with the enzyme activities of peroxidase (POD), catalase (CAT), chitinase (CHI). A decrease in superoxide dismutase (SOD), phenyl alanine ammonia lyase (PAL), b-1, 3-glucanase (GLU) enzyme activities were evident in pest infested plants. Phenolic acids like vanillic acid, syringic acid, cinnamic acid, and p-coumaric acids were mostly found in the infested plants. We demonstrate that the elevated levels of biochemicals, phenolic acids, and enzymes may play a major role in plant defense. Keywords Rice plants Á Enzymes Á Phenols Á Leaf roller Á Yellow stem borer Á Brown plant hopper Abbreviations POD Peroxidase CAT Catalase CHI Chitinase SOD Superoxide dismutase PAL Phenylalanine ammonia lyase GLU b-1, 3-Glucanase YSB Yellow stem borer, Scirpophaga incertulas LR Leaf roller, Cnaphalocrosis medinalis BPH Brown plant hopper, Nilaparvata lugens ROS Reactive oxygen species

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