Impeded Carbohydrate Metabolism in Rice Plants under Submergence Stress

The detrimental effects of submergence on physiological performances of some rice varieties with special references to carbohydrate metabolisms and their allied enzymes during post-flowering stages have been documented and clarified in the present investigation. It was found that photosynthetic rate and concomitant translocation of sugars into the panicles were both related to the yield. The detrimental effects of the complete submergence were recorded in generation of sucrose, starch, sucrose phosphate synthase and phosphorylase activity in the developing panicles of the plants as compared to those under normal or control （i.e. non-submerged） condition. The accumulation of starch was significantly lower in plants under submergence and that was correlated with ADP-glucose pyrophosphorylase activity. Photosynthetic rate was most affected under submergence in varying days of post-flowering and was also related to the down regulation of Ribulose bisphosphate carboxylase activity. However, under normal or control condition, there recorded a steady maintenance of photosynthetic rate at the post-flowering stages and significantly higher values of Ribulose bisphosphate carboxylase activity. Still, photosynthetic rate of the plants under both control and submerged conditions had hardly any significant correlation with sugar accumulation and other enzymes of carbohydrate metabolism like invertase with grain yield. Finally, plants under submergence suffered significant loss of yield by poor grain filling which was related to impeded carbohydrate metabolism in the tissues. It is evident that loss of yield under submergence is attributed both by lower sink size or sink capacity （number of panicles, in this case） as well as subdued carbohydrate metabolism in plants and its subsequent partitioning into the grains.

COMPARISON OF OPTICAL POLARIMETRY AND DIFFUSION TENSOR MR IMAGING FOR ASSESSING MYOCARDIAL ANISOTROPY

We have recently proposed an optical method for assessing heart structure that uses polarized light measurement of birefringence as an indicator of tissue anisotropy.The highly aligned nature of healthy cardiac muscle tissue has a detectable effect on the polarization of light,resulting in a measurable phase shift(“retardance”).When this organized tissue structure is perturbed,for example after cardiac infarction(heart attack),scar tissue containing disorganized collagen is formed,causing a decrease in the measured retardance values.However,these are dependent not only on tissue anisotropy,but also on the angle between the tissue’s optical anisotropy direction and the beam interrogating the sample.To remove this experimental ambiguity,we present a method that interrogates the sample at two different incident beam angles,thus yielding enough information to uniquely determine the true magnitude and orientation of the tissue optical anisotropy.We use an infarcted porcine heart model to compare these polarimetryderived anisotropy metrics with those obtained with diffusion tensor magnetic resonance imaging(DT-MRI).The latter yields the anisotropy and the direction of tissue water diffusivity,providing an independent measure of tissue anisotropy.The optical and MR results are thus directly compared in a common ex vivo biological model of interest,yielding reasonable agreement but also highlighting some technique-specific differences.

Cadmium Accumulation in <i>Marsilea minuta</i>Linn. and Its Antioxidative Responses

The present study was carried out to investigate the extent of cadmium (Cd) accumulation with its possible impact on physiological and biochemical basis of heavy metal tolerance in Marsilea minuta Linn. Cd salt (0 μM, 50 μM and 100 μM) was allowed to absorb by the plants for prolong days in hydroponic culture and a significant deterioration of the plant biomass was recorded. However, roots absorbed more metals than the leaves. Plants recorded a significant rise of superoxide (O-2) and hydrogen peroxide (H2O2). A noticeable amount of protein oxidation and lipid peroxidation were in proportionate to Cd accumulation. Anthocyanin and flavonoid content were decreased as compared to control condition. Superoxide dismutase (SOD), guaiacol peroxidase (GPX) and glutathione reductase (GR) contributed their antioxidative functions according to the Cd doses. The expression of GR was also evident from its activity staining in gel. So, it may suggest that antioxidative enzymes are up regulated and likely to be responsible for tolerance to Cd induced oxidative stress in Marsilea minuta Linn.

Responses of <i>Marsilea minuta</i>L. to Cadmium Stress and Assessment of Some Oxidative Biomarkers

In a hydroponic based experiment, the Cd toxicity is monitored with some cellular responses of Marsilea plant. Initially, plants were grown under varying concentrations (0, 50, 100 and 200 μM of Cd) of cadmium (Cd) with supplementation of 2 mM spermidine (Spd). The oxidative stress developed by Cd overaccumulation was measured with fall in Relative Growth Rate (RGR) by 27.11% to 59.83% growth reduction over control under varying Cd treatments. The retrieval of RGR was recovered by 1.59 folds as compared to the highest concentration of Cd (200 μM) when plants were fed with Spd. A concomitant degradation of chlorophyll was recorded in dose-dependant manner, however, the retrieval was not much pronounced with Spd. On the contrary, the non-oxidant thiol had borne more clarity with ongoing Cd concentration and appeared to be 40.51% increase maximally for GSH: GSSG at the highest concentration of Cd. Spd has minimized the ratio by 27.4%. The recovery of osmotic turgidity was indexed with a sharp rise in glycine betaine by 3.86 folds maximum at the highest concentration of Cd over control which declined by 30.9% with Spd. Another cellular response of treated plants was more evident from their isozymic profiles with regard to superoxide dismutase (SOD), catalase (CAT), guaiacol peroxidase (GPX). The intensity of protein expression was significantly variable but not in band numbers as evident from Cd treated plants. In vitro enzyme assay of catalase showed as declining trend within the limit of 33.13% to 43.22% which was reported by 1.45 folds when Spd was applied. Therefore, from the present study, the cellular responses of Marsilea plant which showed compatibility for their expression with Cd toxicity could be hypothesized as a case of bioindication.