Arsenic (As) contaminated food chains have emerged as a serious public concern for humans and animals and are known to affect the cultivation of edible crops throughout the world. Therefore, the present study was designed to investigate the individual as well as the combined effects of exogenous silicon (Si) and sodium nitroprusside (SNP), a nitric oxide (NO) donor, on plant growth, metabolites, and antioxidant defense systems of radish (Raphanus sativus L.) plants under three different concentrations of As stress, i.e., 0.3, 0.5, and 0.7 mM in a pot experiment. The results showed that As stress reduced the growth parameters of radish plants by increasing the level of oxidative stress markers, i.e., malondialdehyde and hydrogen peroxide. However, foliar application of Si (2 mM) and pretreatment with SNP (100 µM) alone as well as in combination with Si improved the plant growth parameters, i.e., root length, fresh and dry weight of plants under As stress. Furthermore, As stress also reduced protein, and metabolites contents (flavonoids, phenolic and anthocyanin). Activities of antioxidative enzymes such as catalase (CAT), ascorbate peroxidase (APX), guaiacol peroxidase (POD), and polyphenol oxidase (PPO), as well as the content of non-enzymatic antioxidants (glutathione and ascorbic acid) decreased under As stress. In most of the parameters in radish, As III concentration showed maximum reduction, as compared to As I and II concentrations. However, the individual and combined application of Si and NO significantly alleviated the As-mediated oxidative stress in radish plants by increasing the protein, and metabolites content. Enhancement in the activities of CAT, APX, POD and PPO enzymes were recorded. Contents of glutathione and ascorbic acid were also enhanced in response to co-application of Si and NO under As stress. Results obtained were more pronounced when Si and NO were applied in combination under As stress, as compared to their individual application. In short, the current study highlights that Si and NO synergistically regulate plant growth through lowering the As-mediated oxidative stress by upregulating the metabolites content, activity of antioxidative enzymes and non-enzymatic antioxidants in radish plants.
The effects of iron limitation on photosystem II (PSII) composition and photochemical energy conversion efficiency were studied in the unicellular chlorophyte alga Dunaliella tertiolecta. The quantum yield of photochemistry in PSII, inferred from changes in variable fluorescence normalized to the maximum fluorescence yield, was markedly lower in iron-limited cells and increased 3-fold within 20 h following the addition of iron. The decrease in the quantum yield of photochemistry was correlated with increased fluorescence emission from the antenna. In iron-limited cells, flash intensity saturation profiles of variable fluorescence closely followed a cumulative one-hit Poisson model, suggesting that PSII reaction centers are energetically isolated, whereas in iron-replete cells, the slope of the profile was steeper and the calculated probability of energy transfer between reaction centers increased to >0.6. Immunoassays revealed that in iron-limited cells the reaction center proteins, D1, CP43, and CP47, were markedly reduced relative to the peripheral light-harvesting Chl-protein complex of PSII, whereas the [alpha] subunit of cytochrome b559 was about 10-fold higher. Spectroscopic analysis established that the cytochrome b559 peptide did not contain an associated functional heme. We conclude that the photochemical conversion of absorbed excitation energy in iron-limited cells is limited by the number of photochemical traps per unit antenna. 相似文献
Summary Microbial degradation of the leaf litter ofShorea robusta Gaertn. was studied for a period of one year. The changes in the major litter constituents like sugar, starch, hemicellulose,
cellulose and lignin were analysed from the litter kept under the nylon bags, at a month's interval. Four major elements phosphorous,
potassium, magnesium and calcium were also assessed monthly from the decaying litter and the soil. The role of microfungi
in mineral cycling and loss of litter substrates have been correlated. 相似文献
Mammary skin thickening shown on the mammogram was measured in 220 patients with non-inflammatory breast cancer, and the mean skin oedema was derived by taking the mean of five measurements from separate sites on the breast (upper part, lower part, medial part, lateral part, and areola) after subtracting the corresponding figures from the opposite (normal) breast. The prevalence of appreciable oedema (greater than 0.25 mm) was 70% for tumours less than 1 cm and 100% for tumours more than 3 cm in diameter. This measure of oedema correlated positively and significantly with tumour size and lymph node status. In a minimum of 60 months'' follow up patients developing recurrence had significantly higher oedema values. The amount of oedema also predicted recurrence better than lymph node status, tumour size, or tumour stage. Oedema and tumour size, information available preoperatively, provide a simple means of assessing prognosis before definitive treatment. 相似文献
The role of phosphatidylinositol-specific phospholipase C (PIase C) in a) the enigmatic phosphatidylinositol (PI) turnover and b) in our understanding of membrane enzyme-PI interactions is the subject matter of this article. PIase C is present in both procaryotes and eukaryotes. This enzyme is considered to be involved in the cells PI breakdown which occurs in response to several external stimuli. Recent information on the physical properties, Ca2+ requirement, cellular localization and modulation of the activity of PIase C of mammalian systems can help to evaluate the PI turnover from a new angle. Existing evidence suggests that Ca2+-dependent PI breakdown is probably mediated through the cytosolic and particulate PIase C while a Ca2+ independent pathway is catalyzed by a lysosomal enzyme. Apparently PI turnover may be operating through more than one mechanism. The association of this phenomenon with a membrane receptor event linked with “Ca2+ gating” may have to be reconsidered. Modulation of the PIase C activity by unsaturated amphiphiles or the presence of this enzyme in different physico-chemical forms could be a potential regulatory feature.Hydrolysis of membrane PI of a number of cells and tissues by the bacterial PIase C has been shown to cause substantial release of acetylcholinesterase, alkaline phosphatase and 5′-nucleotidase in free, soluble form. Other membrane enzymes, e.g., alkaline phosphodiesterase I, L-leucyl-β naphtyl amidase and Ca2+ or Mg2+ ATPase are not affected. These results indicate a specific interaction between PI and certain enzymes in membranes. The chemical nature of this linkage, whether it is covalent or non-covalent, has also been explored and has provided intriguing insight into this phenomenon. New findings also indicate that hydrolysis of PI by PIase C also can cause modifications in membrane-enzyme activities, e.g., adenylate cyclase. 相似文献
Two new compounds G and H isolated from the roots of Costus speciosus have been characterized as 8-hydroxytriacontan-25-one and Me tritriacontanoat 相似文献
A green house study was conducted on the effect of P and Zn on nodulation and N fixation in chickpea (Cicer arietinum L.) in a loamy sand (Typic Torripsamments) using treatment combinations of five levels of P (0, 25, 50, 100 and 250 ppm),
and six levels of Zn (0, 5, 10, 20, 40 and 100 ppm). The number, dry matter and leghaemoglobin content of nodules, and amount
of N fixed generally increased with Zn alone upto 19 ppm and P alone upto 50 ppm, and decreased with their higher levels.
Application of 25 to 50 ppm P and 5 to 10 ppm Zn counteracted to a greater extent the adverse effect of 40 and 100 ppm Zn,
and 250 ppm P, resp. Maximum nodulation and N fixation (91 to 145% over zero P and Zn, at maturity) was recorded with 25 to
50 ppm P applied along with 5 to 10 ppm Zn. At 64 days, depletion in soil-N was noted, particularly when P was applied, whereas
at maturity there was a gain in soil-N, ranging from 10.5 to 44.5 kg/2×106 kg soil depending upon P and Zn treatments. The increase in nodulation and N fixation with balanced P and Zn nutrition might
be attributed to an increase in leghaemoglobin, and K and Fe concentration in nodules, and increased plant growth, resulting
into enhanced activity of N fixing organisms. The results showed that balanced P and Zn nutrition is essential not only for
plant growth but also for maximum activity of Rhizobium for N fixation.
Work done at Harvana Agricultural University, Hissar, India. 相似文献
1. The distribution of phosphatidylethanolamine, the major lipid of Erwinia carotovora, was investigated in intact bacteria, spheroplasts and outer- and inner-membrane preparations, with the amino-group reagent 2,4,6-trinitrobenzenesulphonic acid. Only 4% was found on the external surface of the outer membrane with 30% on the internal surface, whereas the inner membrane had 27 and 38% on its external and internal surfaces respectively. Some comparative studies were made with three other bacteria. 2. The fluidity of the membranes of E. carotovora was studied by using the fluorescent probe 1,6-diphenylhexa-1,3,5-triene. Results were consistent with the hydrocarbon region of the outer membrane bilayer being less fluid than that of the inner one. 3. On the basis of these and other results a model for the outer- and inner-membrane structures of E. carotovora is proposed. 相似文献
Proteins and lipids in the haemolymph in both the sexes of the Danais chrysippus has been observed during the first gonotropic cycle. The concentration fluctuations in these haemolymph metabolites are correlated with the physiological state of the insect. The total protein and lipid concentration in the haemolymph of unmated females have been found to be low than the concentration found for the normal females although it followed the same type of oscillations in the concentration as have been observed for normal females. 相似文献