Murat Dikilitas

Exogenous application of mannitol and thiourea regulates plant growth and oxidative stress responses in salt-stressed maize (Zea mays L.)

Abstract The mechanism of growth amelioration in salt-stressed maize (Zea mays L. cv., DK 647 F1) by exogenously applied mannitol (M) and thiourea (T) was investigated. Maize seedlings were planted in pots containing perlite and subjected to 0 or 100 mM NaCl in full strength Hoaglands nutrient solution. Two levels of M (15 and 30 mM) or T (3.5 and 7.0 mM) were sprayed to the leaves of maize seedlings 10 days after germination. Salinity stress caused considerable reduction in plant dry biomass, chlorophyll content, and relative water content in the maize plants. However, it increased the activities of catalase (CAT; EC 1.11.1.6), superoxide dismutase (SOD; EC 1.15.1.1), and polyphenol oxidase (PPO; EC 1.10.3.1), and levels of hydrogen peroxide (H2O2) and electrolyte leakage, but it did not change peroxidase (POD; EC 1.11.1.7) activity. Foliar application of M or T was found to be effective in checking salt-induced shoot growth inhibition. Exogenously applied M or T reduced the activities of CAT, SOD, POD, and PPO in the salt-treated maize plants compared to those in the plants not fed with these organic compounds. Salinity increased Na+ contents but decreased those of K+, Ca2 +, and P in the leaves and roots of the maize plants. Foliar-applied M or T increased the contents of K+, Ca2 +, and P, but decreased that of Na+ in the salt-stressed maize plants with respect to those of the salt-stressed plants not supplied with mannitol or thiourea. Mannitol was found to be more effective than thiourea in improving salinity tolerance of maize plants in terms of growth and physiological attributes measured in the present study.

The relationship between plasma aluminum content, lymphocyte DNA damage, and oxidative status in persons using aluminum containers and utensils daily

OBJECTIVES The aim of this study was to explore the in vivo effect of the plasma aluminum content on lymphocyte DNA damage, the plasma protein carbonyl (PC) content, and malondialdehyde (MDA) and total antioxidative capacity (TAC) levels in aluminum exposed and non-exposed humans. DESIGN AND METHODS Peripheral blood samples were collected from in vivo aluminum exposed and non-exposed humans and the above parameters were measured. RESULTS The mean values of lymphocyte DNA damage, plasma MDA, PC levels, and aluminum concentrations were found to be significantly higher in the aluminum exposed group than within the control group (p<0.01). On the other hand, plasma TAC levels were found to be significantly lower in the aluminum exposed group than in the control group (p<0.001). Significant positive correlations were found to exist between lymphocyte DNA damage and the aluminum concentration (r=0.643, p<0.001), DNA damage and MDA (r=0.491, p<0.001), and DNA damage and PC (r=0.548, p<0.01). A negative correlation was found between TAC and DNA damage (r=-0.600 p<0.001) in the aluminum exposed group. CONCLUSION Findings from the study revealed that an increased plasma aluminum concentration was associated with increased oxidative stress and increased DNA damage in aluminum exposed humans.

Mononuclear leukocyte DNA damage and oxidative stress: the association with smoking of hand-rolled and filter-cigarettes.

Cigarette smoking is a major cause of human cancer at various sites, although its carcinogenic mechanisms still remain unestablished. Based on the use of a filter, cigarette smoke can be divided into a gas phase and a tar phase. Both contain different concentrations of oxidants, free radicals and tobacco-specific carcinogens. To explore the effects of both filtered and non-filtered cigarette smoke on DNA damage and oxidative status, we measured the level of mononuclear leukocyte DNA damage by use of the single-cell gel electrophoresis (Comet) assay. We also determined malondialdehyde (MDA), protein carbonyl content (PC) and total antioxidative capacity (TAC) levels in blood plasma of smokers of manufactured filter-cigarettes and of hand-rolled cigarettes. Cotinine levels were also measured in plasma to estimate the degree of smoking. Mononuclear leukocyte DNA damage, plasma MDA, plasma PC and plasma cotinine levels were found significantly higher, while plasma TAC levels were found significantly lower in smokers of filter-cigarettes and smokers of hand-rolled cigarettes, compared with control subjects. TAC levels in hand-rolled and manufactured filter-cigarette smokers were not significantly different from each other. However, the levels of DNA damage, plasma MDA, plasma cotinine, and plasma protein oxidation were significantly higher in hand-rolled cigarette smokers than in filter-cigarette smokers. There was a significant positive correlation between MDA and DNA damage in both hand-rolled cigarette smokers and manufactured filter-cigarette smokers. This study indicates that smoking of hand-rolled cigarettes has stronger genotoxic and oxidative effects on the metabolism than smoking of manufactured filter-cigarettes. We propose that these harmful effects could be attributed to the higher level of oxidants.

Potential of Pseudomonas and Bacillus Isolates as Biocontrol Agents Against Fusarium Wilt of Eggplant

ABSTRACT Plant growth-promoting rhizobacteria (PGPR) are beneficial bacteria found on plant roots that induce growth by a wide variety of mechanisms. Ten isolates of Pseudomonas and Bacillus were isolated from eggplant rhizosphere soil and evaluated for their volatile compound efficacy against mycelial growth of Fusarium oxysporum f. sp. melongenae (Fomg) and tested for their ability to colonize eggplant (Solanum melongena L.) roots in vitro. PGPR strains inhibited mycelial growth of the target pathogen and the percentage of inhibition varied from 38% to 72% by means of inhibitory activities. Pseudomanas aeruginosa (P07–1) and P. putida (P11–4) were determined to be successful colonizers in eggplant seedlings. Also, a pot experiment was conducted to assess the induced resistance to Fusarium wilt of eggplant by PGPR strains. Among the PGPR isolates, P. aeruginosa (P07–1), P. putida (P11–4), P. aeruginosa (85A-2), Bacillus amyloliquefaciens (76A-1) and B. cereus (B10a) significantly reduced Fusarium wilt disease incidence by up to 85%. However, their combination was not more effective in suppressing the disease than the application of those isolates alone. The induction of peroxidase (POX, EC 1.11.1.7) and polyphenol oxidase (PPO, EC 1.14.18.1) enzymes was found to be significantly higher in comparison with the control group. Similarly, the proline levels in eggplants showed an increasing trend with the above isolates. However, catalase (CAT, 1.11.1.6) activity was not found to significantly contribute to the induced resistance mechanism. This study revealed that the promising PGPR isolates could be potentially very useful for the biocontrol of Fomg via enhancing disease resistance in eggplant plants.

Responses of some enzymes and key growth parameters of salt-stressed maize plants to foliar and seed applications of kinetin and indole acetic acid.

The study examined the effects of kinetin (KIN) and indoleacetic acid (IAA) applied as seed treatment or sprayed on leaves of salinity stressed plants. Five -week old maize (Zea mays L. cv. ‘DK 647 F1’) plants were grown in pots containing peat and perlite in 1:1 (v/v) mixture. Different treatments used were: 1) control (nutrient solution alone), 2) salt stress [100 mM sodium chloride (NaCl)], 3) 100 mM NaCl and 1 mM kinetin (KIN), 4) 100 mM NaCl and 2 mM KIN, 5) 100 mM NaCl and 1 mM indole acetic acid (IAA), 6) 100 mM NaCl and 2 mM IAA, 7) 100 mM NaCl and 25 mg L−1 KIN and 8) 100 mM NaCl and 25 mg L−1 IAA. In treatments 7 and 8 application was to the seeds, for treatments 3-6 it was applied to foliage. The seeds were soaked in KIN or IAA solution for 12 h. Salt stress reduced the total dry matter, chlorophyll content, and relative water content (RWC), but increased proline accumulation, activities of superoxide dismutase (SOD; EC 1.15.1.1), peroxidase (POD; EC. 1.11.1.7), catalase (CAT; EC. 1.11.1.6) and polyphenol oxidase (PPO; 1.10.3.1) and electrolyte leakage. Both foliar applications of KIN and IAA treatments overcame to variable extents the adverse effects of NaCl stress on the above mentioned physiological parameters. However, seed treatments with KIN or IAA did not improve salinity tolerance in maize plants. Furthermore, foliar application or seed treatments with KIN and IAA reduced the activities of antioxidant enzymes in the salt stressed-plants. Salt stress lowered some macronutrient concentrations [calcium (Ca) and potassium (K) in leaves and roots, phosphorus (P) in roots] but foliar application of both KIN and IAA increased Ca in both leaves and roots and P in leaves. Foliar application of IAA increased K concentrations in leaves of the salt-stressed plants. Foliar application of KIN and IAA, especially at 2 mM concentration, counteracted some of the adverse effects of NaCl salinity by causing the accumulation of proline and essential inorganic nutrients as well as by maintaining membrane permeability.

Behaviour of Plant Pathogens for Crops Under Stress During the Determination of Physiological, Biochemical, and Molecular Approaches for Salt Stress Tolerance

Agricultural technology is the only way to meet the nutritional needs of the world’s population. In the last century, crop production has significantly increased and has reached its plateau, coincident with the increase in world population. However, a large percentage of the human population still does not have enough food, therefore many are underfed and face malnourishment. The world population will continue to grow along with poverty, environmental health concerns, issues surrounding the availability of clean water sources, etc. By the middle of this century it may reach 10 billion. Therefore, scientists need to try to keep the relationship between crop production and population on an upward slope. To fully understand trends and to determine increases in crop production, many marginal areas need to be included into agricultural lands. If environmental pollution, drought, salinity, disease, and insect problems, as well as the use of irrigation water of marginal quality, are taken into account along with newly added low fertile agricultural lands, many crop plants, for a major part of their growth periods, are grown under adverse conditions. Therefore, now and in the future, scientists have to find physiological, biochemical, and molecular approaches to overcome negative production issues. However, the behaviour and characteristics of plant pathogens have also changed. In this chapter, recent developments in agriculture regarding the production of crops under stress conditions and the behaviour of plant pathogens are evaluated and discussed.

Salts as Potential Environmental Pollutants, Their Types, Effects on Plants and Approaches for Their Phytoremediation

Demand for food dramatically increases as the world gets populated, and this problem is of central attention all over the world. Under these circumstances, the balance between food production and consumption depends on the agricultural productivity. However, an increase in the world population and decrease in the agricultural areas due to many reasons such as industrializations, global warming, use of marginal water etc. have been forcing us to use arable lands efficiently as well as saline-prone areas. Low fertile agricultural areas or non-agricultural areas have to be included into agricultural areas if the food production is to be increased. For this reason, many breeding and amelioration strategies have been evaluated so far, however, a few of them have been found successfully in achieving the goals. Physiological, genetical and biochemical mechanisms in plants are quite complex, therefore, it is very difficult to breed a resistant or tolerant plant against stress. To date, breeding or amelioration strategies have followed one direction, either chemical or biological, they then concentrated on either soil or plant itself, have been tested on a few plants in a few local research stations, e.g., use of mycorrhiza. An amelioration strategy both on soil and plant, which could possibly increase the crop production in saline or polluted areas, enable us to improve soil conditions for a long period of time with little effort and expenses. Salt concentration in the soil could be reduced via drainage as well as using high quality water. On the other hand, economically important crop plants have been bred for their resistance to disease and non-pathogenic stress agents such as drought and salinity and some of them have been made commercially available. However, this has not solved the problem globally, especially for the many crop plants which have to be grown in moderate saline conditions, therefore, an effective alternative approach must be found. In recent years, a new method called “bio-reclamation” or “phytoremediation” has been introduced in many scientific works and reports. It is one of the efficient methods to improve crop production and quality in saline areas aiming to grow halophytes as companion plants with the crop plants. In this chapter, the effect of salt on plants and plant metabolisms and their phytoremediation strategies have been evaluated so that halophytes could possibly be used as companion plants with crop plants without retarding their growth in saline areas.

Effect of Lead on Plant and Human DNA Damages and Its Impact on the Environment

Toxic metals occur naturally in rocks and are released to the environment by weathering. However, release of increasingly larger quantities of toxic metals into the environment have been put our present and future into great danger. Heavy metals are not degradable and do not decompose at all; therefore, they continuously accumulate in soil or our bodies. Lead, in particular, has a great potential to cause disorders in living organisms. Although its toxicity and mode of action have been greatly studied in various studies, it should be remembered that even at a low dose could also be cytotoxic or genotoxic. Even if it does not create genotoxicity at acute exposure, its continuous accumulation results in generating a great amount of reactive oxygen species that eventually create DNA damage and cytotoxicity in living organisms. Low doses could also interact with other abiotic and biotic stressors and create more danger than that of either stress factor alone. Also, pathogenic microorganisms could be invigorated and result in more pathological effects through increased virulence of pathogens. To prevent the potential danger of lead toxicity, we should be aware of its danger in advance of chronic accumulation in the environment or in organisms. Therefore, a new genotoxical method that measures the conditions of DNA should be used via new assays. For remediation of lead, especially from agricultural sites including soil and aquacultural areas, new plant species should be introduced and incorporated with beneficial microorganisms to remediate the polluted environments efficiently. Removal of lead should not only target the absorption of heavy metals, but also should do this in a shorter time.

Antigenotoxic and antioxidant potentials of newly derivatized compound naringenin-oxime relative to naringenin on human mononuclear cells

Abstract We investigated antigenotoxic and antioxidative effects of newly derivatized compound naringenin-oxime (NG-Ox) compared to its mother compound naringenin (NG) against oxidative damage induced by hydrogen peroxide (HP) in human peripheral blood mononuclear cells (PBMC). Antigenotoxic activity was assessed using alkaline single cell gel electrophoresis assay (comet assay). Oxidative status was evaluated by measurement of total antioxidant status, total oxidant status and lipid hydroperoxide levels in the cells. Oxidative stress index was also calculated. Both NG and NG-Ox show a protective effect against HP-induced oxidative damage on PBMC and are able to reduce oxidative stress. The percentage of antigenotoxic and antioxidant potential progressively increased in a dose-dependent manner. However, these activities were found to be more significant in NG-Ox-treated cells than in NG-treated cells. Taken together, these observations provide evidences indicating that both NG and NG-Ox are able to protect cells against oxidative damage and apparently NG-Ox is more effective than NG.

Antioxydant response to biotic and abiotic inducers for the resistance against Fusarium wilt disease in eggplant (Solanum melongena L.)

Abstract Acibenzolar-S-methyl as an abiotic plant activator and a non-host isolate of Fusarium oxysporum on eggplant (F. oxysporum f. sp. melonis) as a biotic inducer were applied to eggplant seedlings in order to confer increased resistance to F. oxysporum f. sp. melongenae, the causal agent of Fusarium wilt of eggplant. Acibenzolar-S-methyl and F. oxysporum f. sp. melonis were applied 72 h before pathogen inoculation and the development of disease symptoms was assessed with a Fusarium yellow rating at 7th, 11th, 14th, 17th and 21th day after inoculation. Pretreatment of eggplants with Acibenzolar-S-methyl and F. oxysporum f. sp. melonis significantly reduced the severity of Fusarium wilt disease. The severity of the disease in positive control plants reached to 92.50% whereas that of acibenzolar-S-methyl and F. oxysporum f. sp. melonis-pretreated seedlings of eggplants was only 32.21% and 21.13%, respectively, 21 days after inoculation. Acibenzolar-S- -methyl and F. oxysporum f. sp. melonis pretreatments resulted in a hypersensitive reaction and triggered the elaboration of histological barriers such as callose and H2O2 synthesis. In situ studies demonstrated that the hydrogen peroxide (H2O2) accumulation and the callose deposition as responses to the pathogen attack started 24 h after inoculation. Acibenzolar- S-methyl and F. oxysporum f. sp. melonis-pretreated plants also showed significant increases in the activity of catalase and polyphenol oxidase enzymes along with the increase of proline and H2O2 content when compared to F. oxysporum f. sp. melongenae-infected plants.