Thiol/Disulfide Homeostasis: A Potential New Peripheral Biomarker in Adolescent Depression.

Background: Thiol-disulfide homeostasis (TDH), one of the most important antioxidants, is involved in the non-enzymatic removal of reactive oxygen molecules in the body and is one of the many methods to measure the level of oxidative stress (OS). In the present study, TDH is investigated in adolescent depression, and its relationship to clinical variables is examined. Methods: Thirty-two (50.0%) patients diagnosed with major depressive disorder (MDD) and without psychotropic drug use and 32 (50.0%) healthy controls were included in the present study. The subjects MDD and control groups were between 13 and 18 years old. Participants completed the DSM-5 Level-2 scales for depression and irritability. A colorimetric method proposed by Erel and Neselioglu was used to analyze the TDH parameters of serum samples. Results: Biochemical analyses of samples from the MDD and control groups showed significant differences between the groups in native thiol (SH) levels (P = .002), disulfide (SS) levels (P = .021), disulfide/total thiol (SS/ToSH) (P = .009), and disulfide/native thiol (SS/SH) (P = .003) levels. Analysis of receiver operating characteristic showed that the area under the curve values with "acceptable discrimination potential" for the TDH parameters were significantly able to discriminate individuals with MDD from healthy controls. Conclusion: Thiol-disulfide homeostasis, one of the OS parameters, was found to be impaired in adolescents with depression. Our results suggest that TDH may contribute to the etiopathogenesis of adolescent MDD and that TDH may be a novel approach to assess OS in adolescent depression.

Exogenous carnitine application augments transport of fatty acids into mitochondria and stimulates mitochondrial respiration in maize seedlings grown under normal and cold conditions.

This study aimed to investigate whether exogenous application of carnitine stimulates transportation of fatty acids into mitochondria, which is an important part of fatty acid trafficking in cells, and mitochondrial respiration in the leaves of maize seedlings grown under normal and cold conditions. Cold stress led to significant increases in lipase activity, which is responsible for the breakdown of triacylglycerols, and carnitine acyltransferase (carnitine acyltransferase I and II) activities, which are responsible for the transport of activated long-chain fatty acids into mitochondria. While exogenous application of carnitine has a similar promoting effect with cold stress on lipase activity, it resulted in further increases in the activity of carnitine acyltransferases compared to cold stress. The highest activity levels for these enzymes were recorded in the seedlings treated with cold plus carnitine. In addition, these increases were correlated with positive increases in the contents of free- and long-chain acylcarnitines (decanoyl-l-carnitine, lauroyl-l-carnitine, myristoyl-l-carnitine, and stearoyl-l-carnitine), and with decreases in the total lipid content. The highest values for free- and long-chain acylcarnitines and the lowest value for total lipid content were recorded in the seedlings treated with cold plus carnitine. On the other hand, carnitine with and without cold stress significantly upregulated the expression level of citrate synthase, which is responsible for catalysing the first reaction of the citric acid cycle, and cytochrome oxidase, which is the membrane-bound terminal enzyme in the electron transfer chain, as well as lipase. All these results revealed that on the one hand, carnitine enhanced transport of fatty acids into mitochondria by increasing the activities of lipase and carnitine acyltransferases, and, on the other hand, stimulated mitochondrial respiration in the leaves of maize seedlings grown under normal and cold conditions.

Melatonin promotes plant growth by maintaining integration and coordination between carbon and nitrogen metabolisms.

KEY MESSAGE: Melatonin-induced growth promotion of maize seedlings is associated with maintaining coordination between gene expressions and activities of key enzymes involved in carbon and nitrogen metabolisms. Melatonin is a pleiotropic molecule that influences many diverse actions to enhance plant growth. The effect of melatonin on maintaining a necessary balance between carbon and nitrogen metabolisms that underpins the growth process in higher plants remains unclear. In this study, the influence of melatonin on nitrogen assimilation, mitochondrial respiration, and photosynthesis, which are major pathways related with carbon and nitrogen metabolism, was investigated on the basis of the seedling growth of maize. Melatonin applications (10, 100, and 1000 µmol L-1) significantly increased the growth parameters assessed by root elongation, plant height, leaf surface area, and the contents of protein, carbohydrate, and chlorophyll in comparison to the control seedlings. They also had a strong encouraging effect on the activities and gene expressions of enzymes (nitrate reductase, nitrite reductase, glutamine synthase, glutamate 2-oxoglutarate transferase, and NADH-glutamate dehydrogenase) involved in the nitrogen assimilation process. While melatonin applications elevated nitrate and nitrite concentrations, they markedly lowered ammonium content compared to control. Similarly, the activity of citrate synthase, the first enzyme of citric acid cycle providing carbon skeleton for nitrogen assimilation, was significantly augmented by melatonin applications. Moreover, melatonin considerably upregulated the gene expressions of citrate synthase and cytochrome oxidase, an enzyme responsible for ATP production. Remarkable increments were recorded at Rubisco activity and gene expressions of Rubisco and Rubisco activase in melatonin-treated seedlings. In conclusion, all these data put together reveal that melatonin-induced growth promotion of maize seedlings resulted from its coordinating effect on carbon and nitrogen metabolisms.

Chitosan production by psychrotolerant Rhizopus oryzae in non-sterile open fermentation conditions.

A new chitosan producing fungus was locally isolated from soil samples collected around Erzurum, Turkey and identified as Rhizopus oryzae PAS 17 (GenBank accession number KU318422.1). Cultivation in low cost non-sterile conditions was achieved by exploiting its ability to grow at low temperature and pH, thus, undesired microbial contamination could be eliminated when appropriate culture conditions (incubation temperature as 15°C and initial pH of the medium as 4.5) were selected. Medium composition and culture conditions were optimized using Taguchi orthogonal array (OA) design of experiment (DOE). An OA layout of L16 (4(5)) was constructed with five most influensive factors at four levels on chitosan production like, carbon source (molasses), metal ion (Mg(2+)), inoculum amount, agitation speed and incubation time. The optimal combinations of factors (molasses, 70ml/l; MgSO4·7H2O, 0.5g/l; inoculum, 6.7×10(6) spores/disc; agitation speed, 150rpm and incubation time, 8days) obtained from the proposed DOE methodology was further validated by analysis of variance (ANOVA) test and the results revealed the increment of chitosan and biomass yields of 14.45 and 8.58 folds from its unoptimized condition, respectively.

Lipoic acid mitigates oxidative stress and recovers metabolic distortions in salt-stressed wheat seedlings by modulating ion homeostasis, the osmo-regulator level and antioxidant system.

BACKROUND: Soil salinity is one of the most detrimental environmental factors affecting the growth of plants and limiting their agricultural productivity. This study investigated whether exogenous lipoic acid (LA) pretreatment plays a role in promoting salt tolerance in wheat seedlings. The seedlings were treated with LA (1.75 mmol L(-1)) and salt (100 mmol L(-1) NaCl) separately and a combination of them. RESULTS: Salt stress significantly reduced relative water content, leaf surface area, ribulose bisphosphate carboxylase expression, and chlorophyll content but increased the content of osmo-regulator protein, carbohydrates and proline. In addition, salinity led to an imbalance in the inorganic composition of wheat leaves. While it elevated Na(+) content compared to control, Ca content and K(+)/Na(+) ratio were reduced. Under saline conditions, despite increases in antioxidant enzyme activity and levels of antioxidant compounds (ascorbate and glutathione), the content of reactive oxygen species (superoxide anion, hydrogen peroxide) and malondialdehyde were higher than in control seedlings. LA significantly promoted osmo-regulator level and antioxidant enzyme activities compared to stressed seedlings alone. Also, it both increased levels of ascorbate and glutathione and regenerated their oxidised forms, thus contributing to maintaining cellular redox status. Similarly, LA prevented excessive accumulation of Na(+) and promoted K(+)/Na(+) ratio and Ca content. Reactive oxygen species content was significantly reduced, and the inhibitions in the above parameters markedly recovered. CONCLUSION: LA reduced salinity-induced oxidative damage and thus contributed to the growth and development of plants in saline soils by modulating ion homeostasis between plant and soil as well as in osmo-regulator content and antioxidant system.

Modulation of alternative oxidase to enhance tolerance against cold stress of chickpea by chemical treatments.

The alternative oxidase (AOX) is the enzyme responsible for the alternative respiratory pathway. This experiment was conducted to examine the influence on cold tolerance ability of chickpea (Cicer aurentium cv. Müfitbey) seedlings of AOX activator (pyruvate), AOX inhibitor (salicylhydroxamic acid (SHAM)) and an inhibitor of the cytochrome pathway of respiration (antimycin A) treatments. 5mM pyruvate, 2µM antimycin A and 4mM SHAM solutions were exogenously applied to thirteen-day-old chickpea leaves and then the seedlings were transferred to a different plant growth chamber arranged to 10/5°C (day/night) for 48h. Cold stress markedly increased the activities of antioxidant enzymes compared to controls. Pyruvate and antimycin A significantly increased the cold-induced increase in antioxidant activity but SHAM decreased it. Cold-induced increases in superoxide anion, hydrogen peroxide, and lipid peroxidation levels were significantly reduced by pyruvate and antimycin A, but increased by SHAM treatment. Pyruvate and antimycin A application increased both the activity and protein expression of AOX in comparison to cold stress alone. However, SHAM significantly decreased activity of AOX but did not affect its expression. Total cellular respiration values (TCRV) supported the changes in activity and expression of AOX. While TCRV were increased by cold and pyruvate, they were significantly reduced by SHAM and especially antimycin A. These results indicate that pyruvate and antimycin A applications were effective in reducing oxidative stress by activating the alternative respiratory pathway as well as antioxidant activity. Furthermore, direct activation of AOX, rather than inhibition of the cytochrome pathway, was the most effective way to mitigate cold stress.

Utilization of Leek (Allium ampeloprasum var. porrum) for inulinase production.

Inulinase production by Rhodotorula glutinis was carried out in this study, using leek (Allium ampeloprasum var. porrum) as an alternative carbon source due to its high inulin content and easy availability. Taguchi orthogonal array (OA) design of experiment (DOE) was used to optimize fermentation conditions. For this purpose, five influential factors (leek concentration, pH, incubation temperature, agitation speed, and fermentation time) related to inulinase production were selected at four convenient levels. The results showed that maximum inulinase activity was obtained as 30.89 U/mL, which was close to the predicted result (30.24 U/mL). To validate the obtained results, analysis of variance (ANOVA) was employed. Consequently, leek has a great potential as an effective and economical carbon source for inulinase production, and the use of Taguchi DOE enhanced enzyme activity about 2.87-fold when compared with the unoptimized condition.

Enhancement of invertase production by Aspergillus niger OZ-3 using low-intensity static magnetic fields.

The aim of this study is to investigate the effect of low-intensity static magnetic fields (SMFs) on invertase activity and growth on different newly identified molds. The most positive effect of SMFs on invertase activity and growth was observed for Aspergillus niger OZ-3. The submerged production of invertase was performed with the spores obtained at the different exposure times (120, 144, 168, and 196 hr) and magnetic field intensities (0.45, 3, 5, 7, and 9 mT). The normal magnetic field of the laboratory was assayed as 0.45 mT (control). Optimization of magnetic field intensity and exposure time significantly increased biomass production and invertase activity compared to 0.45 mT. The maximum invertase activity (51.14 U/mL) and biomass concentration (4.36 g/L) were achieved with the spores obtained at the 144 hr exposure time and 5 mT magnetic field intensity. The effect of low-intensity static magnetic fields (SMFs) on invertase activities of molds was investigated for the first time in the present study. As an additional contribution, a new hyper-invertase-producing mold strain was isolated.

Androsterone-induced molecular and physiological changes in maize seedlings in response to chilling stress.

The aim of study was to elucidate the influence of foliar sprays of androsterone in alleviating detrimental effects of chilling stress in maize seedlings. Eleven-days-old maize seedlings were treated with 10(-9) mol L(-1) androsterone and then transferred to a chamber with temperature of 10/7 °C (day/night) for 3 days. The stress injury was measured in terms of increase in electrolyte leakage, superoxide production and hydrogen peroxide level, and decrease in chlorophyll content. Androsterone application mitigated significantly the chilling-induced stress injury. Under chilling stress, the oxidative damage which was measured as malondialdehyde content was lesser in androsterone-applied seedlings that were associated with greater activities of superoxide dismutase (SOD), catalase (CAT), guaiacol peroxidase (POX), ascorbate peroxidase (APX) and glutathione reductase (GR). Moreover, SOD, POX and APX isozymes exhibited a strong correlation with changes in their activities. Androsterone application enhanced the level of antioxidant compounds like ascorbic acid, glutathione, proline and carotenoid as well as activities of antioxidant enzymes. Similarly, while androsterone treatment increased total antioxidant status, it reduced total oxidant status relative to chilling-stressed seedlings alone. Soluble protein profile was significantly changed by only chilling stress and chilling stress plus androsterone treatment, as well. According to these findings, it is possible to say that androsterone could be used to alleviate the damaging effects of chilling stress by improving antioxidative system in maize seedlings. This is the first study elucidating the effects of androsterone on resistance to chilling stress of plants.

Effects of progesterone application on antioxidant enzyme activities and K+/Na+ ratio in bean seeds exposed to salt stress.

This study aimed to investigate the influence of progesterone, a mammalian sex hormone, on germination of bean (Phaseolus vulgaris L.) seeds exposed to salt stress. The exogenous addition of 10(-6), 10(-8) and 10(-10) M progesterone to the stressing media in which bean seeds were germinated in combination with the salt (100 mM NaCl) stressor induced significant protective changes in the germination and early growth parameters. The mitigating effect of progesterone was evaluated by the measurement of radicle and plumule lengths, activities of antioxidant enzymes superoxide dismutase (SOD), peroxidase (POX) and catalase (CAT). In addition, it is the first study that exhibited changes in K/Na ratio. The obtained results showed that progesterone application stimulated germination and growth of salt-stressed seeds. Similarly, it stimulated significantly SOD, POX and CAT activities compared to both control and salt control. Salt stress significantly increased the lipid peroxidation compared to the control seeds. However, parallel to the increase in antioxidant activity, lipid peroxidation was significantly reduced by progesterone application. The best stimulatory effects on investigated parameters were recorded at 10(-8) M progesterone-applied seeds. On the other hand, salt stress reduced remarkably K/Na ratio by 50% in radicle and by 80% in plumule. However, progesterone application significantly mitigated the reduction in K/Na ratio. These findings clearly demonstrate that progesterone has a positive role in moderate detrimental effects induced by salt.

The availability of bone powder as inorganic element source on growth and development in wheat seedlings.

Bone powder (BP), a by-product of cattle slaughtering plants, consists of fat, protein, amino acids, inorganic elements and vitamins. It is used as bone meal in biomedical and feed industry because of its rich content. In addition, bone contains a large amount of inorganic elements especially calcium (Ca) and phosphorus (P), which the plants need to maintain their physiological and biochemical processes. BP has been used as Ca and P source in agriculture for many years; however, its effects on plant growth and development have not yet been studied in detail. The present study aimed to determine the effects of BP on dry weight and contents of total chlorophyll, soluble protein and sugar as indicators of physiological response in the leaves. For this purpose, bone powder solutions (BPS) were prepared at different concentrations (0.5%, 1%, 1.5% and 2%) and applied to growing media of the 10-day wheat seedlings. Afterward, the 14-day seedlings were harvested, and the effects of BPS on plant response were determined. The results showed that BPS treatments significantly stimulated dry weight and contents of total chlorophyll, protein and sugar compared to control seedlings. The best stimulatory effect of BPS was determined at 1% concentration. According to these results, it is possible to say that BP may be used to meet the inorganic element requirements of plants in poor soils and hydroponic systems.

Exogenous mammalian sex hormones mitigate inhibition in growth by enhancing antioxidant activity and synthesis reactions in germinating maize seeds under salt stress.

BACKGROUND: Mammalian sex hormones (MSH)-progesterone, ß-estradiol and androsterone-enhance plant growth and development by stimulating significant morphological and biochemical parameters under normal conditions. However, there is no report regarding their effects on plants exposed to environmental stress conditions. Therefore, the present study was focused on elucidating the possible positive effects of MSH on seedling growth, antioxidant activity and synthesis reactions in maize seeds exposed to salt stress, one of the most important environmental stresses. For this purpose, the various concentrations (10⁻6, 10⁻8, 10⁻¹° and 10⁻¹² mol L⁻¹) of MSH were studied. RESULTS: Salinity (100 mmol L⁻¹ NaCl) significantly reduced root length and seedling height, whereas MSH treatment significantly ameliorated the adverse effects of salinity on root length and seedling height. On the other hand, although salinity increased soluble protein, soluble sugar and proline content in 7-day-old maize seedlings, these were higher in MSH-treated seedlings. Similarly, MSH treatment augmented superoxide dismutase, peroxidase and catalase activities under salt stress, whereas it decreased superoxide production and lipid peroxidation level. The most favorable concentrations were determined as 10⁻8 mol L⁻¹ for progesterone and ß-estradiol and 10⁻¹° mol L⁻¹ for androsterone. CONCLUSION: Exogenous MSH application was found to have an important ameliorative effect on growth of seeds exposed to salt stress by stimulating antioxidant activity and synthesis reactions. This is the first study investigating the effects of MSH on germination of seeds exposed to stress conditions.

Alleviation of salt stress in wheat seedlings by mammalian sex hormones.

BACKGROUND: Salinity is one of the most serious constraints facing agriculture today. Some mechanical, chemical and biological approaches are being pursued to cope with soil salinity. Although exogenously treated mammalian sex hormones (MSHs), progesterone, ß-estradiol and androsterone, activate significant effects in various biological aspects in plants growing under normal conditions, there is no report investigating their effects on plants growing under salt stress. The present study aimed to investigate whether MSHs could alleviate the destructive effect of salt stress on wheat seedlings and thereby increase their salt tolerance. Wheat leaves were sprayed with 10(-6), 10(-8) and 10(-10) mol L(-1) concentrations of MSH on the ninth day after sowing. MSH-treated seedlings (10-day-old seedlings) were subjected to salt stress for 5 days (between days 10 and 15). RESULTS: At all the concentrations tested, MSH treatment provided a significant protection against to detrimental effects of salt stress in wheat seedlings. It improved dry weight, sugar, proline, protein, chlorophyll and glutathione contents in comparison to salinity alone. Similarly, superoxide dismutase, peroxidase, catalase, ascorbate peroxidase and nitrate reductase activities also were augmented by MSH treatment. On the other hand, increases in lipid peroxidation level, superoxide production and hydrogen peroxide content arising from salt treatment were reduced by MSH treatment. The highest salt tolerance was obtained at the concentrations of 10(-6) mol L(-1) for progesterone and 10(-8) mol L(-1) for ß-estradiol and for androsterone. CONCLUSION: MSHs could be used effectively to protect wheat seedlings from the destructive effects of salt stress by stimulating both enzymatic and non-enzymatic antioxidant mechanism and by promoting levels of osmotic protectants such as proline and sugars resulting in osmotic adjustment, carbon storage and radical scavenging in plants.

Production of carotenoids by Rhodotorula glutinis MT-5 in submerged fermentation using the extract from waste loquat kernels as substrate.

BACKGROUND: The aim of present study was to investigate the feasibility of the hydrolysate extracts from waste loquat kernels as substrate in submerged culture of yeast Rhodotorula glutinis MT-5 for carotenoid production. RESULTS: Loquat kernel was found to have high protein (22.5%) and total carbohydrate (71.2%) contents. Dried and powdered loquat kernels were subjected to acid hydrolysis with 2 mol L⁻¹ HCl. The hydrolysate obtained was used for the preparation of loquat kernel extract and detoxified loquat kernel extract. The detoxification of hydrolysate was performed with Ca(OH)2. Among the 10 R. glutinis isolates, the MT-5 was found to be best in order to produce carotenoid using the extract as substrate. Production media prepared with detoxified loquat kernel extract or loquat kernel extract gave maximum biomass concentrations of 12.64 and 11.37 g L⁻¹, and maximum carotenoid concentrations of 72.36 and 62.73 mg L⁻¹, respectively. CONCLUSION: This study has provided effective processes for the conversion of waste material of plant origin to the extracts which are very rich in term of total fermentable sugar. The practicability of the extracts as fermentation substrate was proven in carotenoid production. To the best of our knowledge, this is the first report on use of this waste material as a substrate in yeast fermentations.

Effects of progesterone, ß-estradiol, and androsterone on the changes of inorganic element content in barley leaves.

The present study was performed to determine the changes in inorganic element content in barley leaves of mammalian sex hormones (MSH). Barley leaves were sprayed with 10(-4), 10(-6), 10(-9), 10(-12), 10(-15) M concentrations of progesterone, ß-estradiol, and androsterone at 7th day after sowing. The plants were harvested at the end of 18 days after treatment with MSH solutions. The inorganic element concentrations were determined using wavelength dispersive X-ray fluorescence spectroscopy technique. Although the all MSH concentrations significantly (p < 0.05) increased the concentrations of calcium, magnesium, phosphorus, sulfur, copper, manganese, aluminum, zinc, iron, potassium, and chlorine, it decreased those of sodium concentration in barley leaves. The maximum changes in the element concentrations were obtained at 10(-9) M for plant leaves treated with progesterone, 10(-6) M for plant leaves treated with ß-estradiol and androsterone. The present study elucidated that MSH significantly (p < 0.05) affected the inorganic element concentrations in barley leaves.

Comparative evaluation of oxidative enzyme activities during adventitious rooting in the cuttings of grapevine rootstocks.

BACKGROUND: This study investigated changes in peroxidase (POX) and polyphenol oxidase (PPO) activities through adventitious rooting in hardwood cuttings of grapevine rootstocks. Three grapevine rootstocks with different propensity to produce adventitious roots were selected: recalcitrant (Ramsey), non-recalcitrant (Rupestris du Lot) and intermediate (99R) cultivars. RESULTS: The averages of root number at 65 days were 96 in Lot, 76 in 99R and 30 in Ramsey. Both enzyme activities characteristically increased before adventitious rooting, regardless of rooting ability of the rootstocks, and then decreased. POX activity increased in Ramsey cuttings at 22 days, in Lot and 99R cuttings at 14 days after planting, and then decreased gradually until 51 days. The highest POX activity was determined in Ramsey rootstock with the highest rooting ability and the lowest activity was determined in the rootstocks with the lowest rooting ability. PPO activity gradually increased in Ramsey rootstock cuttings from 10 days to 22 days, in Lot and 99R cuttings at 14 days, and then decreased until 51 days. A significant correlation was identified between high POX activity and adventitious rooting capability in rootstocks, but the same result was not determined with PPO activity. CONCLUSION: A recalcitrant rooting variety cannot increase POX activity sufficiently before rooting. Therefore applications that could increase POX activity in stem cuttings during rooting may facilitate increased rooting in such rootstocks.

Exogenously treated mammalian sex hormones affect inorganic constituents of plants.

The present study was undertaken to reveal the changes in inorganic constituents of plants exposed to mammalian sex hormones (MSH). Chickpea leaves were sprayed with 10(-4), 10(-6), 10(-9), 10(-12), and 10(-15) M concentrations of progesterone, ß-estradiol, and androsterone at 7th day after sowing. The plants were harvested at the end of 18 days after treatment of MSH solutions and the inorganic components determined using a wavelength-dispersive X-ray fluorescence spectroscopy technique. At all of the concentrations tested, MSH significantly increased the contents of K, S, Na, Ca, Mg, Zn, Fe, P, Cu, and Ni. Interestingly, only Mn and Cl contents decreased. The maximum changes in the inorganic composition were recorded at 10(-6) M for plants treated with progesterone and 10(-9) M for plants treated with ß-estradiol and androsterone.

Effects of extremely low magnetic field on the production of invertase by Rhodotorula glutinis.

Invertase is an important enzyme used in many fields especially in food industry to produce fructose syrups. The current study focused on increasing invertase production by exposing Rhodotorula glutinis to extremely low magnetic fields (ELMF; 0 and 7 mT). For this purpose, the microorganism was allowed to grow in normal magnetic field and ELMF for 72 hours at the same temperature (24 ± 2°C). The fermentation was carried out in submerged culture for 120 hours. The results showed that invertase production is strongly dependent on the growth conditions of the microorganism. Both of the different magnetic fields applied to R. glutinis increased invertase production ranged from 48%-67% when compared with the control. On the other hand, ELMF treatment increased biomass formation about 14%-28% when compared with the control. As a result, magnetic field treatment could effectively be used in the production of invertase by R. glutinis.

Chilling resistance of Phaseolus vulgaris and Brassica oleracea under a high-intensity electric field.

An electric field may have different effects on plant metabolism depending upon its application style and density, and environmental conditions. The effects of an electric field, low temperature, and their combinations on tissue vitality and some physiological variables regarding antioxidant responses of "bean" (Phaseolus vulgaris L. cv. Gina) and "cole" (Brassica oleracea L. cv. Acephale) leaves were studied. Fifteen-day-old seedlings were exposed to an electric field (100 kV m(-1)) for 10 or 40 min prior to cold treatment. In both plant leaves, cold application caused statistically significant increments in total soluble protein levels and selected antioxidant enzyme activities such as catalase, peroxidase and superoxide dismutase activities. However, tissue vitality and H2O2 levels did not change in "cole", while tissue vitality decreased and H2O2 levels increased in "bean". Electric field application itself did not cause any significant changes in "bean" and "cole" leaves. On the other hand, 40 min electric field application increased the deteriorative effect of cold in both plant species, while 10 min electric field augmented the chilling resistance by increasing the tissue vitality and antioxidant enzyme activities resulting in decreased H2O2 levels.

Progesterone and beta-estradiol stimulate seed germination in chickpea by causing important changes in biochemical parameters.

Effects of progesterone and beta-estradiol on morphologic (germination velocity, root and shoot length) and biochemical (activities of alpha-amylase, superoxide dismutase, peroxidase and catalase, H2O2 content, lipid peroxidation) parameters during germination and post-germination stages of chickpea seeds were studied. The seeds germinated at various hormone concentrations (10(-4), 10(-9), 10(-9), 10(-12), 10(-15) M) were harvested at the end of the 1st, 3rd, and 5th day. With comparison to the control, these hormones caused an increment in the number of germinating seeds at the end of days 1 and 3 by accelerating the seed germination. Root and shoot lengths were augmented by both hormones at all hormone concentrations tested. The highest elongation was recorded in 10(-6) M progesterone and 10(-9)-10(-12) M beta-estradiol. Similarly, activities of a-amylase and superoxide dismutase were increased by all concentrations of both hormones, and maximum increases were obtained with 10(-6) M progesterone and 10(-1)-10(-12) M beta-estradiol. In the case of superoxide dismutase activity, not only the H2O2 content but also the peroxidase and catalase activities increased. Lipid peroxidation decreased depending on an increase in the antioxidant enzyme activities. In the present study, it was demonstrated that progesterone and beta-estradiol even at low concentrations increase the germination velocity and resistance to stress conditions by changing the activities of some biochemical pathways.