The phytotoxicity and oxidative damage in response to different concentrations of Hg (0.0, 2.5, 5.0, 10 and 25 μM) were evaluated in wheat plants. The root and shoot growth, content of chlorophyll and total soluble protein declined at 10 and 25 μM Hg. Roots of the plant were more affected as compared to the shoot. The malondialdehyde (MDA) quantity enhanced in the roots of wheat plants treated with 10 and 25 μM Hg and in the leaves of plants treated with 25 μM Hg. The concentration of H 2 O 2 decreased at low concentration and increased at high concentration of Hg. The induction of enzymatic antioxidants (catalase, CAT; ascorbate peroxidase, APX; peroxidase, POX and superoxide dismutase, SOD) was found in the roots and leaves of plants with increased concentration of Hg up to 10 μM and low activities of these enzymes were observed at 25 μM Hg. Also, the level of K, Ca and Mg declined in leaf tissues of Hg treated plants. Thus wheat plants exposed to lower concentrations of Hg did not experience any oxidative stress. However, on treatment with 10 μM Hg, the roots and leaves responded differently. Both the leaves and roots of plants treated with higher concentration of Hg were subjected to comparatively greater oxidative damage and demonstrated that the antioxidative components were not able to remove the stress due to higher concentration of Hg and thus might affect the productivity in wheat plants.

Salivary alpha-amylase (sAA) has been proposed as a sensitive non-invasive biomarker for stress-induced changes in the body that reflect the activity of the sympathetic nervous system. Though several experiments have been conducted to determine the validity of this salivary component as a reliable stress marker in human subjects, the effect of stress induced changes on sAA level in different age groups is least studied. This article reports the activity of sAA in human subjects of different age groups subjected to psychological stress induced through stressful video clip. Differences in sAA level based on sex of different age groups under stress have also been studied. A total of 112 subjects consisting of both the male and female subjects, divided into two groups on basis of age were viewed a video clip of corneal transplant surgery as stressor. Activity of sAA from saliva samples of the stressed subjects were measured and compared with the activity of the samples collected from the subjects before viewing the clip. The age ranges of subjects were 18-25 and 40-60 years. The sAA level increased significantly in both the groups after viewing the stressful video. The increase was more pronounced in the younger subjects. The level of sAA was comparatively more in males than females in the respective groups. No significant change in sAA activity was observed after viewing the soothed video clip. Significant increase of sAA level in response to psychological stress suggests that it might act as a reliable sympathetic activity biochemical marker in different stages of human beings.

The effect of various concentrations of salicylic acid (SA) on the growth, pigment content and the activity of antioxidants was investigated in the laboratory grown wheat plants. The root and shoot growth was affected at higher concentration of SA in early days of growth. The activities of catalase (CAT), ascorbate peroxidase (APX) and guaicol-specific peroxidase (POX) declined with the application of SA (50, 500 and 1000 µM), the decrease being more pronounced with the increase in SA concentrations both in the root and leaf tissues. On the other hand superoxide dismutase (SOD) activity increased with the application of SA. At low concentrations, SA has no effect on the activities of these enzymes in vitro. Salicylic acid at higher concentrations (5-and 10 mM) though inhibited CAT activity, the activities of APX and POX remain unchanged. High concentration of SA increased the level of H 2 O 2 and malondialdehyde both in root and leaf tissues. Thus, SA though has been reported to be a signal molecule for inducing various physiological and morphological attributes in plants, this study indicated the negative effect of the compound on growth and the activity of major enzymatic antioxidants.

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Wheat (Triticum aestivum cv. Sonalika) plants were grown with three different concentrations of salicylic acid (SA; 50/500/1000 μM) for 7 days and the effects on the level of thylakoid photochemical activities were examined. SA treatment stimulated photosystem II‐catalyzed electron flow in all concentrations tested. Photosystem I‐associated electron transport activity was stimulated at low concentrations of SA (50 μM) but at higher concentrations (500 and 1000 μM) the electron transport activity was drastically attenuated. Thylakoids isolated from the leaves of seedlings grown with high concentrations of SA (500 and 1000 μM) showed a substantial reduction in uncoupler (NH4Cl)‐mediated stimulation in electron flow. In addition, they failed to support ADP‐dependent stimulation of electron transport activity and induced a significant reduction in ATPase activity. Incubation of isolated thylakoids with SA, however, had no effect on thylakoid photofunction, indicating no direct effect of SA on photoelectron transport activity. Furthermore, high concentrations of SA specifically reduce the thylakoid cytochrome f554 level. The results suggest that SA, depending on its concentration, imparts differential effects on the photofunction of thylakoids. A low concentration of SA favours photosynthetic activity while the high concentration induces drastic attenuation of photosynthetic activity because of the decline in cytochrome f554.