Salih Mutlu

Effects of salicylic acid and salinity on apoplastic antioxidant enzymes in two wheat cultivars differing in salt tolerance

The effects of salicylic acid (SA) and salinity on the activity of apoplastic antioxidant enzymes were studied in the leaves of two wheat (Triticum aestivam L.) cultivars: salt-tolerant (Gerek-79) and salt-sensitive (Bezostaya). The leaves of 10-d-old seedlings grown at nutrient solution with 0 (control), 250 or 500 mM NaCl were sprayed with 0.01 or 0.1 mM SA. Then, the activities of catalase (CAT), peroxidase (POX) and superoxide dismutase (SOD) were determined in the fresh leaves obtained from 15-d-old seedlings. The NaCl applications increased CAT and SOD activities in both cultivars, compared to those of untreated control plants. In addition, the NaCl increased POX activity in the salt-tolerant while decreased in the salt-sensitive cultivar. In control plants of the both cultivars, 0.1 mM SA increased CAT activity, while 0.01 mM SA slightly decreased it. SA treatments also stimulated SOD and POX activity in the salt-tolerant cultivar but significantly decreased POX activity and had no effect on SOD activity in the saltsensitive cultivar. Under salinity, the SA treatments significantly inhibited CAT activity, whereas increased POX activity. The increases in POX activity caused by SA were more pronounced in the salt-tolerant than in the salt-sensitive cultivar. SOD activity was increased by 0.01 mM SA in the salt-tolerant while increased by 0.1 mM SA treatment in the salt-sensitive cultivar.

Essential oils of catmint (Nepeta meyeri Benth.) induce oxidative stress in early seedlings of various weed species

The essential oils from the aerial parts of catmint (Nepeta meyeri Benth.) were analyzed by hydrodistillation with GC–MS. Fourteen compounds were identified in the yellowish essential oil of the plant, representing more than 99.07% of the oil, of which the major components were found to be 4aα,7α,7aβ-nepetalactone (83.4%) and 4aα,7α,7aα-nepetalactone (8.83%). The oils were characterized by relatively high content of oxygenated monoterpenes, and were tested on the germination and antioxidative systems in early seedlings of seven weed species (Amaranthus retroflexus L., Bromus danthoniae Trin., Bromus intermedius Guss., Chenopodium album L., Cynodon dactylon L., Lactuca serriola L., and Portulaca oleracea L.) and autotoxicity. The essential oil of N. meyeri inhibited seed germination by more than 50% in three weed species (B. danthoniae, B. intermedius, and L. serriola) when applied at a concentration of 0.01%. When the same oils were applied at 0.02% concentration, the inhibition of germination was more than 70% in two weeds (C. album and C. dactylon) and was 100% in four weeds (A. retroflexus, B. danthoniae, B. intermedius, and L. serriola). The essential oils increased CAT activity in all the weed species and decreased SOD activity, except in A. retroflexus. POX activity did not exhibit a revealing situation in the weed species tested. The essential oils increased the level of lipid peroxidation and hydrogen peroxide (H2O2) concentration in all the weeds studied. Our results show that the essential oils of N. meyeri have an important phytotoxic effect on seed germination and, consequently, seedling growth by exhausting antioxidative system of the weeds. The phytotoxic activity of the essential oils may be attributed to their relatively high content of oxygenated monoterpenes, especially 4aα,7α,7aβ-nepetalactone. It can be suggest that the essential oils of N. meyeri have the potential to be used as a bioherbicide.

Protective role of salicylic acid applied before cold stress on antioxidative system and protein patterns in barley apoplast

This study was carried out to better understand the role of salicylic acid (SA) applied before cold stress in the cold tolerance mechanism. Two barley (Hordeum vulgare) cultivars, cold-sensitive (Akhisar) and cold-tolerant (Tokak), were used and 0.1 mM SA was applied to 7-d-old barley seedlings growing under control conditions (20/18 °C). The seedlings were transferred to cold chamber (7/5 °C) at the age 14, 21, and 28 d. After three days, the leaves were harvested to determine the activities of apoplastic antioxidant enzymes, such as superoxide dismutase (SOD), catalase (CAT), and peroxidase (POX) and ice nucleation activity and electrophoretic patterns of apoplastic proteins. Cold treatment decreased the activities of all enzymes in cold-sensitive cultivar, however, it increased CAT and POX activities in cold-tolerant cultivar. Exogenous SA increased enzyme activities in both cultivars. Ice nucleation activity increased by cold treatment, especially in 17-d-old seedlings in both cultivars. In addition, SA treatment increased ice nucleation activity in all examined samplings in both cultivars. SA treatment caused accumulation or de novo synthesis of some apoplastic proteins. The results of the present study show that exogenous SA can improve cold tolerance by regulating the activities of apoplastic antioxidative enzymes, ice nucleation activity, and the patterns of apoplastic proteins.

Allelopathic effect of Nepeta meyeri Benth. extracts on seed germination and seedling growth of some crop plants

In order to evaluate the allelopathic potential of Nepeta meyeri Benth., the effects of aqueous extracts (0.125, 0.25, 0.5, 1, 2.5 and 5%) prepared from roots and leaves of N. meyeri were studied on the seed germination and seedling growth of several economically important crops (barley, wheat, canola, safflower, and sunflower). Both the root and leaf extracts of N. meyeri caused a general phytotoxic effect on the seed germination and seedling growth of barley and sunflower at all concentrations. However, both the root and leaf extracts significantly increased the seedling growth of wheat, especially at the lower concentrations 0.125, 0.25 and 0.5%, whereas the higher concentrations had a neutral effect. The seed germination and the seedling growth of canola and safflower were also generally improved by both extracts, especially at lower concentrations. However, these advantages were not observed at higher concentrations, at which the extracts mostly had a phytotoxic effect on canola and safflower. The Allelopathic activity of N. meyeri depended on whether the extract was derived from the leaf or root parts of the plant. The maximum allelopathic effect occurred with leaf extracts. The results demonstrate that the aqueous extracts from N. meyeri have allelopathic potential and should be evaluated as an allelopathic species, presenting a risk or advantage to seed germination and seedling growth of crop or weed plants.

Effects of exogenous nitric oxide in wheat seedlings under chilling stress

The effects of nitric oxide (NO) on chilling tolerance (contents of hydrogen peroxide (H2O2) and superoxide anion (O2 –) and lipid peroxidation level (malondialdehyde, MDA)) and the activities of antioxidant enzymes (superoxide dismutase (SOD), peroxidase (POX) and catalase (CAT)) were investigated in the leaves of wheat (Triticum aestivum L.) exposed to chilling. NO treatment was carried out through spraying of sodium nitroprusside (SNP), which is a donor of NO. To do this, SNP concentrations of 0.1 and 1 mM were applied on the leaves of 11-day plants and the plants were then exposed to chilling conditions (5/2°C) for 3 days. The chilling stress treatment increased both the activities of antioxidant enzymes and the levels of MDA, H2O2 and O2 –. Similarly, NO treatment enhanced SOD, POX and CAT activities under chilling stress, whereas it decreased H2O2 and O2 . – contents as well as MDA level. The most effective concentration was determined as 0.1 mM SNP. Exogenous SNP application as a donor of NO was found to have an important ameliorative effect on cold tolerance of seedling exposed to chilling stress by stimulating antioxidant enzyme activity.

Exogenous salicylic acid alleviates cold damage by regulating antioxidative system in two barley (Hordeum vulgare L.) cultivars

ABSTRACT In this work, the time-dependent effect of exogenous salicylic acid (SA) applied before cold stress was investigated on the regulation of antioxidative respond mechanisms in two barley (Hordeum vulgare L.) cultivars (Akhisar and Tokak) differed in cold tolerance. SA (0.1 mM) was applied to 7-days old barley seedlings growing under control conditions (20/18°C). After this application, the seedlings were transferred to cold conditions (7/5°C) at different times (7, 14, 21 and 28 days) for 3 days. Then, the contents of malondialdehyde (MDA), hydrogen peroxide (H2O2) and the activities of antioxidant enzymes such as superoxide dismutase (SOD), catalase (CAT) and peroxidase (POX) were determined in the leaves (control, cold and SA + cold) from the seedlings harvested at 10, 17, 24 and 31 days. Moreover, the effect of cold stress was evaluated on the endogenous SA level at the both cultivars by comparing to control plants. The MDA content increased in the cold treatment while it decreased in the SA treatment at all the days studied at the both cultivars. The SA + cold treatment could have a variable effect on H2O2 content at the tolerant barley (Tokak) while decreased its content at the sensitive cultivar (Akhisar). The SA + cold treatment could increase the activities of POX and SOD at both cultivars, but it increased the CAT activity at the tolerant cultivar while decreased at the sensitive cultivar. In addition, the content of endogenous SA was decreased by cold stress at all the days studied at the barley cultivars as compared to control plants. The results show that the SA treatment could be effective on the regulation of the parameters studied at cold conditions until 31 days after SA application, and the importance of exogenous SA treatment before cold stress. It was concluded that exogenous and endogenous SA could play an ameliorating role on cold tolerance by regulating reactive oxygen species and the activities of antioxidative enzymes in both cold-sensitive and cold-tolerant cultivars of barley.

Cement dust pollution induces toxicity or deficiency of some essential elements in wild plants growing around a cement factory

In the present study, it was aimed to determine the effects of cement dust pollution on contents of some significant essential elements (P, S, K, Ca, Fe and Cl) in wild plants (Medigago varia, Anchusa leptophylla, Euphorbia orientalis, Lactuca serriola, Artemisia spicigera, Crambe orientalis, Convolvulus sepium and Senecio vernalis) using wavelength-dispersive spectrometer X-ray fluorescence technique. Plant samples were collected from different locations around a cement factory which is located at Askale about 50 km from Erzurum (Turkey). The element contents in the plant specimens that existed in both 0–100 m (dense dusted) and 2000 m (undusted) areas were compared. P, S, K and Cl contents were found to be high in the plants growing in areas 0–100 m from the cement factory, compared to same plants at 2000 m far from the factory. However, Ca and Fe contents were determined to be low in plants growing in 0–100 m area from the factory. Results of the study can contribute to understand how mineral deficiency and toxicity lead to detrimental effects on plant growth and development in the fields contaminated by cement dust.

Genotoxic effects of catmint (Nepeta meyeri Benth.) essential oils on some weed and crop plants

This study investigates the genotoxicity of the essential oils extracted from the aerial parts of catmint (Nepeta meyeri Benth.) against two weeds (Bromus danthoniae and Lactuca serriola) and two crop plants (Brassica napus and Zea mays). The essential oils of N. meyeri analyzed by gas chromatography–mass spectrometry contained 14 compounds, with 4aα, 7α, 7aβ-nepetalactone (83.4%), 4aα, 7α, and 7aα-nepetalactone (8.83%) as the major components. The oils were diluted (25, 50, 100, and 150 ppm) and the solutions were applied to seeds or leaves of these plants. The study compared the germination percentage and random amplified polymorphic DNA (RAPD) results with the control group. The results showed that the oils had a strong inhibitory activity and caused a change in RAPD profiles in terms of variation in band intensity, loss of bands, and appearance of new bands compared with the control group. The results suggested that RAPD analysis could be applied as a suitable biomarker assay for the detection of genotoxic effects of plant allelochemicals. This study indicates the genotoxical potential of N. meyeri essential oils on weed and crop plants.

Alleviation of high salt toxicity-induced oxidative damage by salicylic acid pretreatment in two wheat cultivars.

Role of exogenous salicylic acid (SA) in the antioxidative response to salt toxicity of two wheat (Triticum aestivum) cultivars (Gerek-79 and Bezostaya) was investigated. Hydroponic growth environment of 10-day wheat seedlings grown under normal conditions (22/20°C) was adjusted to 0.0, 0.25, 0.50 and 0.75 M of salt (NaCl), and then freshly prepared SA solutions (0.0, 0.01 and 0.1 mM) were once sprayed on leaves of the same seedlings. Activities of superoxide dismutase (SOD), peroxidase (POX) and catalase (CAT) were determined in fresh leaves obtained from 15-day seedlings. Treatment with SA alone increased all the antioxidant activities in Gerek-79. However, the same treatments with SA decreased the activities of CAT and SOD in Bezostaya, while increased that of POX. Salt applications alone increased the activities of POX and SOD, while decreased that of CAT in Bezostaya. The same salt applications increased the POX activity, while decreased the activities of CAT and SOD in Gerek-79. In plants under saline conditions, except 0.75 M NaCl, treatments with SA increased the activities of CAT, POX and SOD in both the varieties compared with plants applied salt alone. In plants applied with 0.75 M NaCl, however, treatments with SA decreased CAT activity. Results showed that salt toxicity caused a derangement in the regulation of antioxidant enzyme activities by decreasing CAT activity especially in both the varieties, but treatments with SA could turn back the derangement in the antioxidative enzymes caused by salt toxicity. SA can involve in increasing salt tolerance by regulating the activities of antioxidant enzymes in wheat cultivars exposed to salt toxicity.

Mistletoe (Viscum album) reduces the growth of the Scots pine by accumulating essential nutrient elements in its structure as a trap

Key messageWe found mistletoe accumulates nutrient elements in its structure as a trap and causes a severe drought stress in the Scots pine in dry summer seasons.AbstractThe mistletoe [Viscum album ssp. austriacum (Wiesbaur) Vollm.] is a hemiparasitic plant, and its infestation is known to play an important role on the mortality of Scots pines (Pinus sylvestris L.), but there is little knowledge about its action mechanism. This study, therefore, tried to gain a better understanding of the destructive effect of the mistletoe on the growth and water uptake mechanism of the Scots pine. Identical needles from neighboring plants (healthy and infested) were harvested in the middle of each month (from April to October 2013) and used as research material. Infestation success of the mistletoe was investigated by evaluating the contents of the endogenous nutrient elements such as potassium, phosphorus, calcium, sulfur, magnesium, iron, copper, zinc, manganese, boron, nickel, and sodium in both mistletoe leaves and the needles of healthy and infested Scots pine. Its effects were also evaluated by determining the content of water, chlorophyll, and dry matter, and the length of the newly formed needles of the healthy and infested trees. Mistletoe infestation led to a decrease in the availability of water and mineral nutrients, and caused a powerful inhibition on the growth parameters such as chlorophyll, dry matter, and the length of needles by accumulating the essential nutrient minerals in its structure. The findings of this study indicate that the mistletoe accumulates the nutrient elements in its structure as a trap and causes a severe drought stress in the Scots pine in dry summer seasons, thereby playing a potent role in the increasing mortality rate in the Scots pine.