Influence of salicylic acid on morphological and physiological responses of banana (Musa acuminata cv. 'Berangan', AAA) shoot tips to in vitro water stress induced by polyethylene glycol

Abstract Growth and productivity of banana is seriously restricted by water deficit. Salicylic acid (SA) induces biotic and abiotic stress tolerance in crops. To study the ameliorative effects of SA on water stress in banana (Musa acuminata cv. 'Berangan', AAA), shoot tip explants with 8 mm in size were treated with varying SA concentrations (0, 1, 2 and 3 mM) and incubated on MS media containing different levels (0, 1, 2 and 3 %) of PEG in vitro. After 2 months, proliferation rate, fresh weight increase, relative water content, chlorophyll level, proline accumulation, malondialdehyde (MDA) and H 2 O 2 contents were measured and analyzed. The results indicated that with increasing levels of PEG, proliferation rate, fresh weight increase, relative water content and chlorophyll concentrations were significantly decreased. The SA concentrations improved shoot tips performance by increasing proliferation rate, fresh weight increase and relative water content. Although non SA -treated shoot tips were not significantly responsive to increasing levels of PEG in terms of elevated proline content, they responded positively to supply of SA by showing significant increase in proline and chlorophyll contents under water stressed conditions. SA treatments also enhanced plant tolerance against oxidative stress. This was observed through significant reduction in H 2 O 2 and MDA contents of SA -treated shoot tips under water stress conditions. The results revealed that exogenous application of SA helped to reduce the harmful effects of water deficit on banana regenerants in vitro

Modified-release hydrocortisone to provide circadian cortisol profiles

Context: Cortisol has a distinct circadian rhythm regulated by the brain's central pacemaker. Loss of this rhythm is associated with metabolic abnormalities, fatigue, and poor quality of life. Conventional glucocorticoid replacement cannot replicate this rhythm. Objectives: Our objectives were to define key variables of physiological cortisol rhythm, and by pharmacokinetic modeling test whether modified-release hydrocortisone (MR-HC) can provide circadian cortisol profiles. Setting: The study was performed at a Clinical Research Facility. Design and Methods: Using data from a cross-sectional study in healthy reference subjects (n = 33), we defined parameters for the cortisol rhythm. We then tested MR-HC against immediate-release hydrocortisone in healthy volunteers (n = 28) in an open-label, randomized, single-dose, cross-over study. We compared profiles with physiological cortisol levels, and modeled an optimal treatment regimen. Results: The key variables in the physiological cortisol profile included: peak 15.5 mu g/dl (95% reference range 11.7-20.6), acrophase 0832 h(95% confidence interval 0759-0905), nadir less than 2 mu g/dl (95% reference range 1.5-2.5), time of nadir 0018 h (95% confidence interval 2339-0058), and quiescent phase (below the mesor) 1943-0531 h. MR-HC 15 mg demonstrated delayed and sustained release with a mean (SEM) maximum observed concentration of 16.6 (1.4) mu g/dl at 7.41 (0.57) h after drug. Bioavailability of MR-HC 5, 10, and 15 mg was 100, 79, and 86% that of immediate-release hydrocortisone. Modeling suggested that MR-HC 15-20 mg at 2300 h and 10 mg at 0700 h could reproduce physiological cortisol levels. Conclusion: By defining circadian rhythms and using modern formulation technology, it is possible to allow a more physiological circadian replacement of cortisol. (J Clin Endocrinol Metab 94: 1548-1554, 2009

Individualizing clomiphene citrate for induction of ovulation : searching for covariates

Clomiphene citrate (CC) has been the first line of treatment for induction of ovulation in patients with anovulatory infertility since 1962. It is administered as a mixture of two geometric isomers, Enclomiphene (En) and Zu-clomiphene (Zu) citrate in the ratio 62%:38%. The En isomer is perceived to be more active. A prediction model of response to CC was developed utilizing physical and biochemical characteristics of patients but this model has not been vahdated in a set of patients independent of those used to develop the model. It examines an existent nomogram for the identification of patient resistant to CC therapy and indicates that the nomogram is not sufficiently sensitive and specific to be useful in clinical practice. It shows that obesity could change the pharmacokinetics of Zu but not En. It provides early indications for a hypothesis that therapeutic outcome may be linked to interindividual variation in the exposure to the metabolite formed by CYP2D6. This may explain the lack of any direct relationship between the concentrations of the parent compound and response.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Effect of Salinity on Growth and Physiological Parameters of Four Olive (OleaeuropaeaL.) Cultivars underGreenhouse Conditions

Introduction: Salinity is a common abiotic stress that seriously affects crop production around the world, particularly in arid and semi-arid regions.The deleterious effects of salinity on plant growth are associated with low osmotic potential of soil solution (water stress), nutritional imbalance, specific ion effect (salt stress), or a combination of these factors. Olive is one of the most important fruit crops in Iran and the world. Despite olive has been classified as moderately salt tolerant plant, poor quality of irrigation water in association with salt build-up soils has reduced the yields, especially in arid and semi-arid regions of Iran. The tolerance of the olive to salt is to a great extent depends on the cultivar. Selecting salinity-resistant cultivars is one of the most important strategies used for mitigating salinity effects on olive. Therefore, this study was performed to assess the salt tolerance of four olive cultivars under greenhouse condition. Materials and Methods: For this purpose, one-year-old rooted cuttings of Iranian olive cultivars (‘Dakal’, ‘Shiraz’, ‘Zard’) and non-Iranian cultivar ‘Amigdal’ were grown in the research greenhouse of Agricultural College, Isfahan University of Technology of Iran. Plants were grown in plastic pots. The pots were 180 mm in diameter and 20 mm in depth with volume of 7 L. The minimum and maximum temperatures during the experiment period were 19 and 35˚C, respectively. After sticking the cuttings, the pots with uniform plants were subjected to the treatment with 0 (control), 100, 150 or 200 mMNaCl. The electrical conductivities of these solutions were 0.003, 10.52, 15.43 and 19.55 dS m-1, respectively. To avoid osmotic shock, the NaCl concentration was gradually increased. The layout was a 4×4 factorial experiment based oncompletely randomized design, with four replications. The experimental measurements were carried out three months after beginning the salt treatments. Results and Discussion:The results showed that salt stress and cultivar hadsignificant effects on all of vegetative and physiological parameters. Injury rating valueof plants wasfound to increase significantly as the salt concentration was raised. Among the cultivars, the highest injury rating value (2.75) belonged to Amigdal cultivar, while the lowest means (2.00) was related to Dakal cultivar. By increasing the salinity level, stem heightincreasing ratesignificantly decreased. The lowest means (18.17%) belonged to 200 mMNaCl treatment, showing 81.83% decrease compared with control. Among the cultivars, Zard showed the highest means of increase in stem height (71.75%). Leaf area influenced significantly by salinity, sothat the lowest means of leaf area (35.05%) was recorded for200 mMNaCl treatment, showing a 69.91% decrease compared with the control. The highest leaf area belonged to Shiraz cultivar, which had a significant difference with Zard and Amigdal cultivars. Compared with the control, salinity caused 50.83% and 54.36% decreases in shoot fresh and dry weight in 200 mMNaCl, respectively. The highest shoot fresh and dry weightswere recorded forZard cultivar. The lowest shoot fresh and dry weights were observed forAmigdal cultivar.Increment of salinity concentration significantly declined root fresh and dry weight. Among the cultivars, the highest means of root fresh weightbelonged to Amigdal cultivar, whereas the lowest was related to Shiraz cultivar. The highest and lowest root dry weightswere observed forDakal and Amigdal cultivars, respectively.Salinity significantly decreased relative water content.The lowest leaf relative water content (66.04%) was recorded in 200 mMNaCl treatment, showing a 23.43% decrease compared with the control.Zard cultivar showed the highestleafrelative water content. Salinity stress decreased chlorophyll fluorescence in leaves of salt-treated olive plants. At 200 mMNaCl, leaf chlorophyll fluorescence was minimal as compared to control and other salt levels. The highest leaf chlorophyll fluorescence ratio (0.74) was recorded forZard cultivar. However, Amigdal cultivar showed the lowest means for this index (0.60).Salinity significantly decreasedleaf chlorophyll content.The lowest leaf chlorophyll content (69.39%) was recorded in 200 mMNaCl, showing a 66.80% decrease compared with the control.Among the cultivars, Zard showed the highest leaf chlorophyll content (170.33). In the present study, the increase in proline content in the NaCl-treated plants was noted, with the highest level being attained with 200 mMNaCl. The highest proline content (1.03 µmol.g-1 F.W.)was observed in Zard cultivar. Salinity stress increased malondialdehyde content in the leaves of salt-treated plants. The highest malondialdehyde content was obtained from leaves of plants treated with 200 mMNaCl. The highest malondialdehyde content was recorded in Amigdal cultivar.Shirazl cultivar showed the lowest malondialdehyde content. In this study, the correlation betweenvegetative and physiological parameters of olive plants subjected to salt stress was analysed. These correlations suggested that salt injury symptoms was negatively correlated with relative water content, leaf chlorophyll fluorescence and leaf chlorophyll content, but positively correlated with proline content and malondialdehyde content. Conclusion: In overall, this investigation revealed that salt stress had aninhibitory effect on the vegetative growth of olive plants.The responses of olive cultivars to salt stress suggested that Zard and Shiraz cultivars were more tolerant and ‘Amygdal’ was the most sensitive to changes in the salt levels

Effect of Silicon on Growth and Development of Strawberry under Water Deficit Conditions

Water stress is a major factor that limits agricultural crop production. Silicon (Si) is generally considered as a beneficial element for the growth of higher plants, especially for those grown under stressful environment. This study was conducted to examine the effects of Si on growth and development of strawberry (Fragaria × ananassa ‘Camarosa’) under water stress conditions. A factorial experiment, in a completely randomized design, was used to investigate the effects of three irrigation levels and four Si treatments consisting of 0, 5, 10, and 15 mmol·L−1 potassium silicate (K2SiO3). The results showed that an increase in the levels of water stress caused a decrease in most of the quantitative characteristics such as specific leaf area, chlorophyll fluorescence, net photosynthesis rate, and stomata conductance; addition of Si significantly increased most of the mentioned factors; water stress increased electrolyte leakage, proline, and water use efficiency (WUE); Si treatment significantly decreased transpiration rate and improved chlorophyll content and WUE. Water stress stimulated mineral nutrient absorption whereas Si application decreased it under water stress. In conclusion, it was found that in most of the investigated factors, 10 mmol·L−1 potassium silicate had the best effect on growth and development of strawberry. Besides, Si application had beneficial effects on strawberry plants and the addition of it could alleviate water stress. Keywords: Fragaria × ananassa, potassium silicate, water stress, photosynthesis, mineral nutrien

Morphological, physiological and antioxidant response of Stevia rebaudiana under in vitro agar induced drought stress

In this investigation, the response of Stevia rebaudiana Bertoni was studied in different in vitro drought conditions. A method based on agar concentration in different levels (6, 8, 10, 12, 14 gl-1) was used to induce some drought stress levels. Agar concentrations can make a meaningful difference in biochemical, physiological, and antioxidant responses of the Stevia. Under the stress condition, the highest accumulation of proline content (50%) and malondialdehyde (MDA) (42%) were recorded in the highest concentration of agar. Moreover, antioxidant enzyme activities, ascorbate peroxidase (17%), catalase (53%), and peroxidase (30%) have been drastically enhanced from 8 gl-1 agar. Current results indicated that using agar as a water stress agent could be effectively exploited as an efficient method in modeling the in vitro drought stress in Stevia rebaudiana