Esra G. Bagci

Silicon increases boron tolerance and reduces oxidative damage of wheat grown in soil with excess boron

The effect of silicon on the growth, boron concentrations, malondialdehyde (MDA) content, lipoxygenase (LOX) activity, proline (PRO) and H2O2 accumulation, and the activities of major antioxidant enzymes [superoxide dismutase (SOD), catalase (CAT), and ascorbate peroxidase (APX)] and non-enzymatic antioxidants (AA) of wheat grown in soil originally with toxic B concentrations were investigated. Applied of 5.0 and 10.0 mM Si to the B toxic soil significantly increased Si concentration of the wheat and counteracted the deleterious effects of B on shoot growth. The contents of PRO, H2O2, MDA, and LOX activity of wheat grown in B toxic soil were significantly reduced by Si treatments. Compared with control plants, the activities of SOD, CAT, APX and content of AA were decreased by applied Si. Based on the present work, it can be concluded that Si alleviates B toxicity of wheat by preventing oxidative membrane damage and also translocation of B from root to shoot and/or soil to plant.

Influence of silicon on antioxidant mechanisms and lipid peroxidation in chickpea (Cicer arietinum L.) cultivars under drought stress

Abstract The effects of exogenous silicon (Si) on leaf relative water content (RWC), and the growth, Si concentrations, lipid peroxidation (MDA), lipoxygenase (LOX) activity, proline and H2O2 accumulation, non-enzymatic antioxidant activity (AA) and the activity of some antioxidant enzymes (superoxide dismutase, SOD; catalase, CAT; ascorbate peroxidase, APX) in shoots of ten chickpea cultivars grown under drought were investigated. Drought stress decreased the growth of all the cultivars while applied Si improved the growth at least five of the 10 chickpea cultivars. Silicon applied to the soil at 100 mg kg−1 significantly increased Si concentrations of the cultivars and counteracted the deleterious effects of drought in 5 of the ten chickpea cultivars by increasing their RWC. In most cultivars tested H2O2, proline and MDA content and LOX activity were increased by drought whereas application of Si decreased their levels. APX activity was increased by drought but it was depressed by Si. In general, SOD and CAT activities of the cultivars were decreased by drought. Depending on cultivars, the CAT activity was decreased, and increased or unchanged in response to applied Si, while the SOD activity of the cultivars increased or unchanged by Si. The non-enzymatic antioxidant activity of the cultivars was also increased by Si. These observations implied an essential role for Si in minimizing drought stress-induced limitation of the growth and oxidative membrane damage in chickpea plants.

Effect of drought stress implemented at pre- or post-anthesis stage on some physiological parameters as screening criteria in chickpea cultivars

Drought is one of the most important factors limiting chickpea production in arid and semi-arid regions. There is little information regarding genotypic variation for drought tolerance in chickpea cultivars. Screening for drought tolerance is very important. It is essential to identify the physiological mechanisms of drought tolerance to complete conventional breeding program. Glasshouse experiment was carried out to study the genotypic variation among 11 chickpea (Cicer arietinum L.) cultivars. Plants were grown either under optimum conditions or drought stress was implemented at pre-or post-anthesis stages. The drought susceptibility index (DSI) was used as the measure of drought tolerance. Relationships between DSI and excised-leaf water loss (RWL), relative water content (RWC), membrane permeability, ascorbic acid, proline, and chlorophyll contents, lipid peroxidation, and hydrogen peroxide concentrations were determined in order to find out whether these physiological parameters could be used as the genotypic selection criteria for drought tolerance. The results of this study indicated that there was a wide variation in tolerance to drought stress among the chickpea cultivars, which could be exploited in breeding new chickpea cultivars with high drought tolerance. The results also demonstrated that drought-tolerant cultivars had a higher RWC, ascorbic acid and proline concentrations, but lower RWL and membrane permeability in comparison to drought-sensitive cultivars. The significant and a well defined relationships between DSI and RWC, RWL, ascorbic acid, proline, and membrane permeability were found. It was concluded that these parameters could be instrumental in predicting the drought tolerance of chickpea cultivars.

Interspecific Facilitative Root Interactions and Rhizosphere Effects on Phosphorus and Iron Nutrition Between Mixed Grown Chickpea and Barley

ABSTRACT A glasshouse study was conducted to investigate the effects of interspecific complementary and competitive root interactions and rhizosphere effects on phosphorus (P) and iron (Fe) nutrition of mixed grown chickpea (Cicer arietinum L.) and barley (Hordeum vulgare L.). In order to provide more physiological evidence on the mechanisms of interspecific facilitation, we determined phosphatase activities in plant and rhizosphere, and root ferric reducing capacity (FR), Fe-solubilizing activity (Fe-SA) and rhizosphere pH. The results of the experiment revealed that biomass yield of barley was significantly increased by associated chickpea as compared to monocultured barley, while mixed cropping caused a slight decreases in the biomass yield of chickpea. The rhizosphere was strongly acidified under chickpea and chickpea/barley mixed cropping and this acidification, in turn, increased the available P, Fe(II) and DTPA-Fe concentrations in the rhizosphere. Fe-solubilizing activity (Fe-SA) and ferric reducing (FR) capacity of the roots were higher in both species grown in mixed culture relative to their monoculture which may improve Fe nutrition of both species. Leaf acid phosphatase (APase, EC 3.1.3.2) activity was higher in both plants under mixed cropping that may improve P nutrition of barley by chickpea.

Recovery of bean plants from boron-induced oxidative damage by zinc supply

The effects of zinc on growth, boron uptake, lipid peroxidation, membrane permeability (MP), lypoxygenase (LOX) activity, proline and H2O2 accumulation, and the activities of major antioxidant enzymes (superoxide dismutase (SOD), catalase (CAT), and ascorbate peroxidase (APX)) in bean plants were investigated under greenhouse conditions. Treatments consisted of control, 20 mg/kg B, and 20 mg/kg B plus 20 mg/kg Zn. When the plants were grown with 20 mg/kg Zn, B toxicity was less severe. Zinc supplied to soil counteracted the deleterious effects of B on root and shoot growth. Excess B significantly increased and Zn treatment reduced B concentrations in shoot and root tissues. Applied Zn increased the Zn concentration in the roots and shoots. While the concentrations of H2O2 and proline were increased by B toxicity, their concentrations were decreased by Zn supply. Boron toxicity increased the MP, malondialdehyde content, and LOX activity in excised bean leaves. Applied Zn significantly ameliorated the membrane deterioration. Compared with control plants, the activity of SOD was increased while that of CAT was decreased and APX remained unchanged in B-stressed plants. However, application of Zn decreased the SOD and increased the CAT and APX activities under toxic B conditions. It is concluded that Zn supply alleviates B toxicity by preventing oxidative membrane damage.

Variations in essential and non-essential element composition and yield of silage corn fertilized with sulfur

Abstract The effect of sulfur fertilization on the silage yield and essential and non-essential element composition of silage corn was investigated at the Experimental Field of Research and Experiment Station of the Ankara University during the years 2002 and 2003. The experimental design was a randomized complete block with five replications. Sulfur was applied at 1000 (S1) and 1500 (S2) kg ha−1 as gypsum. Element concentration of the plants was measured by polarized energy dispersive X-ray fluorescence (PEDXRF). Sulfur fertilization increased S concentrations and improved silage corn yield for both years. Applied S reduced P and Mo concentrations, increased Fe and Mn concentrations, and had no significant effect on the K, Ca, Mg, Zn and Cl concentrations of silage corn. Non-essential element composition of silage corn was also influenced by S fertilization. Applied S significantly increased Sr and Pb, reduced Si, Ba and U, while had no effect on Na, Ti, Ni, Br and Rb concentrations of silage corn. In the current work, essential and non-essential element concentrations of silage corn in 2002 and 2003 years under our experimental conditions were as follows; 1.58–1.89 S, 1.07–1.046 P, 14.3–15.9 K, 8.35–9.20 Ca, 3.34–4.28 Mg, 0.26–0.53 Na, 1.36–2.46 Cl, 38.4–42.1 Si as g kg−1, and 2.06–3.13 Mo, 140–144 Fe, 6.08–17.69 Zn, 104–116 Mn, 9.37–12.2 Cu, 23.9–22.6 Ti, 2.10–2.31 Ni, 6.54–6.71 Br, 7.04–8.74 Rb, 94.8–118.8 Sr, 24.0–31.51 Ba, 1.20–2.22 Pb and 3.17–4.07 U as mg kg−1.

Combined Effect of Arsenic and Phosphorus on Mineral Element Concentrations of Sunflower

This study was undertaken to examine the combined effect of soil‐applied phosphorus (P) and arsenic (As) on P, As, potassium (K), calcium (Ca), magnesium (Mg), silicon (Si), iron (Fe), manganese (Mn), zinc (Zn), copper (Cu), titanium (Ti), rubidium (Rb), strontium (Sr), barium (Ba), lantanium (La), and cerium (Ce) concentrations of sunflower plants under glasshouse conditions determined by polarized‐energy‐dispersive x‐ray fluorescence (PEDXRF). Three levels of As (0, 30, and 60 mg kg−1) and four levels of P (50, 100, 200, and 400 mg kg−1) were applied to soil‐grown plants. Increasing levels of both As and P significantly increased As concentrations in the plants. Plant growth was significantly reduced with increased As supply regardless of applied P levels. Arsenic toxicity caused significant increases in the concentrations of Mn, La and Ce, but it decreased K, Ca, Mg, Si, Fe, Zn, Cu, Rb, and Sr concentrations. Applied P increased the concentrations of Ti, Sr, and Ba and decreased Zn and Cu. In conclusion, the use of P fertilizers in As‐contaminated soils should be carefully considered in respect to increased As, Ti, Sr, and Ba availability and reduced Zn and Cu availability.