Shuvasish Choudhury

Reactive oxygen species signaling in plants under abiotic stress

Abiotic stresses like heavy metals, drought, salt, low temperature, etc. are the major factors that limit crop productivity and yield. These stresses are associated with production of certain deleterious chemical entities called reactive oxygen species (ROS), which include hydrogen peroxide (H2O2), superoxide radical (O2−), hydroxyl radical (OH−), etc. ROS are capable of inducing cellular damage by degradation of proteins, inactivation of enzymes, alterations in the gene and interfere in various pathways of metabolic importance. Our understanding on ROS in response to abiotic stress is revolutionized with the advancements in plant molecular biology, where the basic understanding on chemical behavior of ROS is better understood. Understanding the molecular mechanisms involved in ROS generation and its potential role during abiotic stress is important to identify means by which plant growth and metabolism can be regulated under acute stress conditions. ROS mediated oxidative stress, which is the key to understand stress related toxicity have been widely studied in many plants and the results in those studies clearly revealed that oxidative stress is the main symptom of toxicity. Plants have their own antioxidant defense mechanisms to encounter ROS that is of enzymic and non-enzymic nature . Coordinated activities of these antioxidants regulate ROS detoxification and reduces oxidative load in plants. Though ROS are always regarded to impart negative impact on plants, some reports consider them to be important in regulating key cellular functions; however, such reports in plant are limited. Molecular approaches to understand ROS metabolism and signaling have opened new avenues to comprehend its critical role in abiotic stress. ROS also acts as secondary messenger that signals key cellular functions like cell proliferation, apoptosis and necrosis. In higher eukaryotes, ROS signaling is not fully understood. In this review we summarize our understanding on ROS and its signaling behavior in plants under abiotic stress.

Arsenic stress in rice: Redox consequences and regulation by iron

Arsenic (As) contamination is a serious hazard to human health and agriculture. It has emerged as an important threat for rice cultivation mainly in South Asian countries. In this study, we investigated the effect of iron (Fe) supplementation on arsenic (As(V)) induced oxidative stress responses in rice (Oryza sativa L.). Rice seedlings treated with As(V) for 24 and 48 h in presence or absence of 2.5 mM Fe after which the root and shoot tissues were harvested for analysis. The results indicate significant (p ≤ 0.05) reduction in root and shoot length/dry biomass. Supplementation of Fe showed improved growth responses under stress as compared to As(V) alone. The scanning electron microscopy (SEM) analysis of roots under As(V) treatment for 48 h showed major alterations in root structure and integrity, although no noticeable changes were observed in Fe - supplemented seedlings. Significantly high (p ≤ 0.05) accumulation of As(V) was observed in root and shoot after 24 and 48 h of stress. However, under Fe - supplementation As accumulation in root and shoot were considerably low after 24 and 48 h of As(V) treatment. The hydrogen peroxide (H2O2) and malondialdehyde (MDA) content in both root and shoot increased significantly (p ≤ 0.05) after 24 and 48 h of As(V) treatment. In Fe - supplemented seedlings, the levels of H2O2 and MDA were considerably low as compared to As(V) alone. Ascorbate (AsA) and glutathione (GSH) levels also increased significantly (p ≤ 0.05) under As(V) stress as compared to control and Fe-supplemented seedlings. Activities of catalase (CAT) and superoxide dismutase (SOD) were significantly (p ≤ 0.05) high after 24 and 48 h of As(V) treatment as compared to Fe-supplemented seedlings. The gene expression analysis revealed up-regulation of metallothionein (MT1, MT2) and nodulin 26-like intrinsic protein (NIP2;1) genes after 5d of As treatment, while their expressions were repressed under Fe-supplementation. Our results indicate that Fe regulates oxidative stress and promotes growth under As stress.

Ethnomedicinal plants used by Chorei tribes of Southern Assam, North Eastern India

Article history: Objective: To explore and enumerate the medicinal plants used by the Chorei tribe residing in Sourthern Assam part of North Eastern India in the treatment of various ailments. Methods: Systematic and intensive field surveys were conducted in Chorei inhabited parts of Southern Assam part of North East India to collect information on medicinal plants used by them in treatment of various ailments. Data was collected through structured questionnaires and personal observations made during the field visit. Results: A total of 53 different medicinal plants were recorded along with their vernacular names, parts used and mode of utilization by the Chorei tribes. Each of the plants was categorized according to their use in treatment of particular disease. Conclusions: The present study revealed that the Chorei tribe is primarily dependent of medicinal plant for treatment of various ailments.

Volatile Constituents of the Aerial and Underground Parts of Curcuma aromatica Salisb. from India

ABSTRACT The leaves, petioles and rhizomes of Curcuma aromatica Salisb. (Zingiberaceae) from Assam, India, were subjected to steam distillation. The resulting essential oils were analyzed by high-resolution GC and GC/MS. The leaf, petiole and rhizome oils contained more than 51, 50 and 61 components respectively, of which 43, 41 and 53 constituents have been identified, accounting for about 96.8%, 86.3% and 86.3% of the bulk of the respective oils. The major components in the leaf, petiole and rhizome oils were found to be 1,8-cineole (20.0%, 8.8% and 9.3%, respectively), camphor (18.0%, 16.8% and 25.6%), germacrone (11.8%, 0.2% and 10.6%), isoborneol (6.4%, 6.8% and 8.2%) and camphene (9.4%, 1.2% and 7.4%). Additional notable constituents included limonene (8.6%) in the leaf oil, caryophyllene oxide (8.7%), patchouli alcohol (8.4%) and elsholtzia ketone (6.0%) in the petiole oil, and curzerenone (10.9%) in the rhizome oil.

Essential oils of Litsea monopetala (Roxb.) Pers. : a new report from India

Abstract Litsea monopetala (Roxb.) Pers. (Lauraceae) is a “muga” silk worm fodder tree in Northeast India, with the local name “sualu.” The oils of this species, obtained by steam distillation of the fresh fruits, flowers and bark, were examined by high resolution GC and GC/MS for the first time. From the more than 50 compounds separated by GC, about 40 to 45 compounds have been identified in the various oils, accounting for 89–5% to 93.8% of the oils. The major components of the flower oil were α-caryophyllene alcohol (13.9%), pentacosane (11.4%), caryophyllene oxide (9.5%), humulene oxide (9.5%) and tricosane (8.1%). The more volatile fruit oil consisted mainly of decanal (26.7%), nonanol (16.8%) and capric acid (15.5%). The bark oil was mainly composed of aldehydes, alcohols and acids, of which tetradecanal (30.2%), tridecanol (11.3%), myristic acid (10.5%) and tridecanal (9.4%) predominated.

RP-HPLC simultaneous estimation of betulinic acid and ursolic acid in Carissa spinarum

Carissa spinarum is a well-known medicinal plant which has been reported for its anthelmintic, antipyretic, antiviral, antimicrobial and antitumour activities. In this study, a reverse-phase high-performance liquid chromatographic method was developed for the simultaneous estimation of betulinic acid (BA) and ursolic acid (UA) in the methanol extract of C. spinarum root. The method was further validated for linearity, limit of detection (LOD = 3.3σ/S), limit of quantification (LOQ = 10σ/S), precision, accuracy and ruggedness. The linear response was obtained using the equation, y = 511.5x+17603 (r2 = 0.9920) and y = 2886x+6821 (r2 = 0.9935) for BA and UA, respectively. The LOD and LOQ were found to be 0.268 ± 0.520 μg mL− 1, 0.878 ± 0.183 μg mL− 1 for BA (0.58% w/w) and 3.140 ± 0.36 μg mL− 1, 8.820 ± 0.85 μg mL− 1 for UA (1.09% w/w), respectively. The %RSD of precision and recovery of BA and UA was < 2.0%. The proposed method was simple, accurate, specific, precise and reproducible.

Constituents of the Flower and Fruit Oils of Persea bombycina (King ex Hook, f.) Kost from India

Abstract The essential oils obtained by hydrodistillation from the fresh flowers and fruits of Persea bombycina (King ex Hook. f.) Kost (previously called Machilus bombycina King) were examined by a combination of high resolution GC and GC/MS. The flower oil contained more than 65 compounds of which the major constituents were found to be caryophyllene oxide (19.4%), (E)-nerolidol (14.5%), 11-dodecenal (11.2%) and 11-dodecenoic acid (9.8%). The composition of the fruit oil was entirely different. Among the more than 60 (mostly oxygenated) constituents, the furanoid forms of trans- (8.0%) and cis-linalool oxide (7.3%) were major components, but many compounds could not be identified.