S. Roy Chowdhury

Bio: S. Roy Chowdhury is an academic researcher from Indian Council of Agricultural Research. The author has contributed to research in topics: Null (mathematics) & Corchorus capsularis. The author has an hindex of 6, co-authored 21 publications receiving 220 citations. Previous affiliations of S. Roy Chowdhury include Central Tuber Crops Research Institute & University of Burdwan.

Hydrogen peroxide metabolism as an index of water stress tolerance in jute

Abstract: Two species of jute plants Corchorus capsularis L. (cv. JRC 212) and C. olitorius L. (cv. JRO 632) were subjected to water stress for 2 and 4 days by withholding water. The relative water content (RWC) decreased in both plants under water stress but to a greater extent in C. olitorius. The C. olitorius seedlings also showed greater membrane injury than C. capsularis seedlings under water stress as was evident from injury index data. Water stress increased glycolate oxidase (EC 1.1.3.1.) activity more in C. olitorius than in C. capsularis. The activity of superoxide dismutase (SOD, EC 1.15.1.1.) and catalase (EC 1.11.1.6.) decreased under water stress and their decrease was higher in C. olitorius than in C capsularis. The level of hydrogen peroxide and lipid peroxidation also increased in both plants under water stress and the increase was higher in C. olitorius than in C. capsularis seedlings. Under comparable external water stress, C. capsularis seedlings showed lower membrane damage, lower H2O2 accumulation and lower lipid peroxidation than C. olilorius which may be taken as indicative of higher water stress tolerance capacity of the former.

Diurnal changes in chlorophyll fluorescence and light utilization in Colocasia esculenta leaves grown in marshy waterlogged area

Abstract: Diurnal cycle of chlorophyll fluorescence parameters was done in Colocasia esculenta L. (swamp taro) grown in marshy land under sun or under shade. The sun leaves maintained higher electron transport rate (ETR) and steady state to initial fluorescence ratio (Fs/F0) than shade leaves. In spite of lower ETR, higher photochemical quenching (PQ), and effective quantum yield of photosystem 2 (ΦPS2) was evident in shade plants compared to plants exposed to higher irradiance. ETR increased linearly with increase in irradiance more under low irradiance (r2 = 0.84) compared to higher irradiance (r2 = 0.62). The maximum quantum yield of PS 2 (Fv/Fm) did not differ much in sun and shade leaves with the exception of midday when excess of light energy absorbed by plants under sun was thermally dissipated. Hence swamp taro plants adopted different strategies to utilize radiation under different irradiances. At higher irradiance, there was faster decline in proportion of open PS 2 centers (PQ) and excess light energy was dissipated through non-photochemical quenching (NPQ). Under shade, absorbed energy was effectively utilized resulting in higher ΦPS2.

Direct control of lysosomal catabolic activity by mTORC1 through regulation of V-ATPase assembly

Abstract: Abstract Mammalian cells can acquire exogenous amino acids through endocytosis and lysosomal catabolism of extracellular proteins. In amino acid-replete environments, nutritional utilization of extracellular proteins is suppressed by the amino acid sensor mechanistic target of rapamycin complex 1 (mTORC1) through an unknown process. Here, we show that mTORC1 blocks lysosomal degradation of extracellular proteins by suppressing V-ATPase-mediated acidification of lysosomes. When mTORC1 is active, peripheral V-ATPase V 1 domains reside in the cytosol where they are stabilized by association with the chaperonin TRiC. Consequently, most lysosomes display low catabolic activity. When mTORC1 activity declines, V-ATPase V 1 domains move to membrane-integral V-ATPase V o domains at lysosomes to assemble active proton pumps. The resulting drop in luminal pH increases protease activity and degradation of protein contents throughout the lysosomal population. These results uncover a principle by which cells rapidly respond to changes in their nutrient environment by mobilizing the latent catabolic capacity of lysosomes.

Water stress induced changes in concentrations of proline and total soluble sugars in nodulated alfalfa (Medicago sativd) plants

Abstract: Susceptibility of alfalfa (Medicago saliva L. cv. Aragon) nodules and leaves to water stress has been investigated. Nodule acetylene reduction activity (ARA), leaf CO2 exchange rate (CER) as well as soluble protein, proline and total soluble sugar (TSS) contents were determined during drought. Water status was estimated as water potential (Ψw) and Relative water content (RWC) of the respective tissues. Maximum rates of ARA required higher Ψw than CER. Nodules had lower RWC for a given Ψw than leaves. Water stress reduced soluble protein content in both tissues; however, the decline in soluble protein content was detected at greater Ψw in nodules than in leaves. Proline and TSS increased in leaves and nodules, and again the threshold Ψw triggering such accumulation was higher in nodule tissues. Oior results suggest that alfalfa nodules are more susceptible to water shortage than leaves. Effects of accumulated TSS and proline upon leaf and nodule physiology are discussed in relation to protein stability (proline), pH control (proline) and osmotic adjustment (proiine and TSS). The TSS accumulation induced by water stress suggests that substrate shortage would not be the primary effect of drought on nodule activity.

Drought induces oxidative stress in pea plants

Abstract: Pea (Pisum sativum L. cv. Frilene) plants subjected to drought (leaf water potential of ≈-1.3 MPa) showed major reductions in photosynthesis (78‰), transpiration (83‰), and glycolate oxidase (EC 1.1.3.1) activity (44‰), and minor reductions (≈18‰) in the contents of chlorophyll a, carotenoids, and soluble protein. Water stress also led to pronounced decreases (72–85‰) in the activities of catalase (EC 1.11.1.6), dehydroascorbate reductase (EC 1.8.5.1), and glutathione reductase (EC 1.6.4.2), but resulted in the increase (32–42‰) of non-specific peroxidase (EC 1.11.1.7) and superoxide dismutase (EC 1.15.1.1). Ascorbate peroxidase (EC 1.11.1.11) and monodehydroascorbate reductase (EC 1.6.5.4) activities decreased only by 15‰ and the two enzymes acted in a cyclic manner to remove H2O2, which did not accumulate in stressed leaves. Drought had no effect on the levels of ascorbate and oxidized glutathione in leaves, but caused a 25‰ decrease in the content of reduced glutathione and a 67‰ increase in that of vitamin E. In leaves, average concentrations of catalytic Fe, i.e. Fe capable of catalyzing free-radical generation by redox cycling, were estimated as 0.7 to 7 μM (well-watered plants, depending on age) and 16 μM (water-stressed plants); those of catalytic Cu were ≈4.5 μM and 18 μM, respectively. Oxidation of lipids and proteins from leaves was enhanced two- to threefold under stress conditions and both processes were highly correlated. Fenton systems composed of the purported concentrations of ascorbate, H2O2, and catalytic metal ions in leaves produced hydroxyl radicals, peroxidized membrane lipids, and oxidized leaf proteins. It is proposed that augmented levels and decompartmentation of catalytic metals occurring during water stress are responsible for the oxidative damage observed in vivo.

Antioxidant responses to drought in sunflower and sorghum seedlings

Abstract: To determine if antioxidant responses to drought differ between C3 and C4 plants, we grew Sorghum bicolor (C4 ) and Helianthus annuus (C3 ) under either watered or dry conditions in a growth chamber. Levels of leaf enzymatic antioxidants (ascorbate peroxidase, catalase, guaiacol peroxidase, dehydroascorbate reductase, monodehydroascorbate reductase, glutathione reductase and superoxide dismutase), nonenzymatic antioxidants (ascorbate, glutathione and carotenoids) and stress parameters (Chl and malondialdehyde [MDA]) were determined. Under watered and drought conditions, Chl contents and leaf relative water contents (RWC) were higher in sorghum than in sunflower; however, MDA levels were higher in sunflower than in sorghum. Under watered conditions, inherent levels of antioxidants were not consistently higher or lower in sorghum than in sunflower. In response to drought, levels of antioxidants, Chl and MDA showed increase, decrease or remained unchanged depending on crop, duration of drought and kind of antioxidants. Duration of drought was divided arbitrarily into three stages. At an early stage of drought (watering had stopped for 3-4 d) when soil water content (WC) and leaf RWC had decreased only in sunflower, drought generally did not affect levels of antioxidants and stress parameters. At a middle stage of drought (watering had stopped for 5-6 d) when soil WC had decreased for both sorghum and sunflower but leaf WC and RWC had decreased only in sunflower, drought changed levels of some antioxidants in sunflower and sorghum. At a late stage of drought (watering had stopped for 7-8 d) when soil WC, leaf WC and RWC had decreased in sorghum and sunflower, most parameters studied were affected by drought. Because of the differential effect of drought, levels of antioxidants were not consistently higher or lower in sorghum than in sunflower under drought. These results show that, under both drought and watered conditions, sorghum does not have consistently higher or lower antioxidant levels than sunflower, and that antioxidant responses to drought differ in C3 and C4 plants.

Stress and stress coping in cultivated plants

Abstract: 1. The overall implications of biological stress.- 2. Oxidative stress.- 3. Salt stress.- 4. Chilling stress.- 5. Freezing stress.- 6. Desiccation.- 7. Water and drought stress.- 8. Heat stress.- 9. Anaerobic stress - flooding and ice-encasement.- 10. Environmental pollution stress.- Epilogue.