Turkish Journal of Biology Turk J Biol (2013) 37: 350-360 http://journals.tubitak.gov.tr/biology/ © TÜBİTAK Research Article doi:10.3906/biy-1209-12

Role of growth promoting rhizobacteria on antioxidant enzyme activities and production of under water deficit stress

1, 1 2 Mansour GHORBANPOUR *, Mehrnaz HATAMI , Kazem KHAVAZI 1 Department of Medicinal , Faculty of Agriculture and Natural Resources, Arak University, Arak, Iran 2 Department of Soil Biology, Soil and Water Research Institute, Karaj, Iran

Received: 08.09.2012 Accepted: 04.12.2012 Published Online: 16.05.2013 Printed: 17.06.2013

Abstract: This study examined the effects of inoculation with 2 rhizobacteria strains, Pseudomonas putida (PP) and Pseudomonas fluorescens (PF), on growth parameters, chlorophyll, proline, relative water content (RWC), antioxidant enzyme activities (including superoxide dismutase (SOD), peroxidase (POX), and catalase (CAT)), tropane alkaloids (such as hyoscyamine (HYO) and (SCO)), and production of Hyoscyamus niger under 3 water deficit stress (WDS) levels, i.e. 30% (W1), 60% (W2), and 90% (W3) water depletion of field capacity. The results showed that inoculation with PP and PF strains minimized the deleterious effects of WDS on growth parameters. The activities of SOD and POX in root and leaf were increased to a significant extent with inoculation of PP and PF, and also with WDS treatment, whereas CAT activity decreased with increasing WDS, except for in plants treated with the PF strain. The maximum proline, HYO, and SCO content were recorded in PF-treated plants under W3 conditions. In contrast, the highest root and shoot alkaloids yield were obtained in plants bacterized with PP against W1 conditions. PP was the most effective strain under low WDS, PF had the highest efficiency in improving the growth and alkaloid production in the presence of severe (W3) WDS. Integrative use of effective plant growth promoting rhizobacteria (PGPR) and WDS could be an encouraging and eco-friendly strategy for increasing alkaloid yield and content in Hyoscyamus niger organs.

Key words: Hyoscyamus niger, rhizobacteria, water deficit stress, tropane alkaloids, antioxidant enzymes

1. Introduction Infection with microorganisms, as well as physical Black henbane (Hyoscyamus niger) is an important factors such as osmotic stresses, induce particular medicinal plant of the family . It is a rich secondary metabolite pathways (6). Among the numerous source of tropane alkaloids such as hyoscyamine (HYO) microorganisms in the rhizosphere, some have positive and scopolamine (SCO), which are generally used in effects on plant growth promotion. These microorganisms medicine as , antispasmodic, mildly pain- are plant growth promoting rhizobacteria (PGPR) such as relieving, hypnotic, hallucinogenic, pupil-dilating, and Pseudomonas putida (PP) and Pseudomonas fluorescens sedative compounds (1). Due to its fewer side effects on (PF), which colonize the rhizosphere and roots of many the nervous system, SCO is preferred and has higher plant species and confer beneficial effects to plants. commercial demand (2). Because of the complex chemical Although drought stress negatively affects the growth structures of these alkaloids, industrial synthesis has and development of field crops, the contents of second­ been found to be prohibitively expensive; therefore they ary metabolites are mostly increased through the positive are mainly obtained from plant resources of the family effects on the metabolic pathways of active compounds’ Solanaceae like belladona or Datura stramonium synthesis in medicinal plants. This type of abiotic stress (3). These metabolites have also been reported in other affects the plant water status at the cellular and whole plant plant families, e.g., Orchidaceae, Euphorbiaceae, Cruciferae, level, causing specific as well as unspecific reactions and and Convolvulaceae, and in the fungus Amanita muscaria damage (7). (4). A plant’s fine roots without secondary growth have Environmental stresses impair the electron transport been found to be the principal site of tropane alkaloid system, leading to the generation of reactive oxygen -2 - production, where the main enzymes of their biosynthetic species (ROS) such as H2O2, O , and OH that cause pathway are localized (5). rapid cell damage (8). These compounds initiate damage * Correspondence: [email protected] 350 GHORBANPOUR et al. / Turk J Biol in the chloroplast and cause a cascade of damaging Iran. Black henbane seeds generally have a low germination effects, including chlorophyll destruction. Moreover, rate under normal laboratory conditions. Therefore, seeds –1 root meristem activity is very sensitive to ROS; these were treated with 250 mg L gibberellic acid (GA3) for 48 h compounds were accumulated in the differentiation zone, at room temperature (25 ± 0.5 °C) for breaking dormancy where root hairs grow (9). In plants the metabolism of and accelerating germination. After that, seeds were ROS is kept in dynamic balance. Under water deficit stress surface-sterilized in 70% ethanol for 2 min, then in 25% (WDS), the balance is upset and antioxidant systems such commercial bleach (containing 6% sodium hypochlorite) as superoxide dismutase (SOD), peroxidase (POX), and for 10 min, and finally rinsed with sterile distilled water. catalase (CAT), along with the antioxidant ascorbic acid Subsequently, seeds were placed in petri dishes on 2 layers and glutathione, scavenge the reactive free radicals (10). of filter paper (Whatman no. 1) moistened with 4 mL Inoculation of plants with native suitable microorganisms of distilled water. After 3 days, 90% of seeds germinated may decrease the deleterious effects of environmental steadily (with 1–2 mm radicle length). stresses and increase stress tolerance of plants by a variety 2.2. Bacterial strains and inoculation of mechanisms, including synthesis of phytohormones Based upon the efficiency of rhizobacteria in enhancing such as auxins, solubilization of minerals like phosphorus, the seedling growth index, whose results are in separate production of siderophores, and increases in nutrient preliminary in vitro and sand culture assays, 2 of the uptake, leaf area, chlorophyll, and soluble leaf protein most effective PGPR strains with different multiple content (11). In recent years, many experiments have been conducted on the role of microbial association like plant growth promoting activities, namely PP-168 and Arbuscular mycorrhizal symbiosis and PGPR in drought- PF-187 (shortened to PP and PF, respectively), from 20 stressed crop plants (12). However, there have been no strains were selected and used in this study (Table 1). To comparative studies about the role of PP and PF strains prepare inocula, a single colony of each PGPR strain was under WDS on antioxidant enzyme activities or secondary transferred to 100-mL flasks containing 25 mL of tryptone metabolite production (especially tropane alkaloids) in soybean broth (TSB) and grown aerobically in the flasks such a commercially important medicinal plant. A review on a rotating shaker (120 rpm) for 72 h at 28 °C. The of the literature revealed that in most of the studies no bacterial suspension was then diluted in sterile distilled 9 –1 investigations have been performed regarding alkaloid water to achieve a final concentration of 10 CFU mL . yield and the content of these metabolites on a whole The prepared suspensions were used to inoculate henbane plant basis under respective treatments. The objective of radicles and culture media under aseptic conditions. the present study was to investigate the growth promoting 2.3. Plant growth conditions and water deficit stress effects of 2 promising rhizobacteria strains, Pseudomonas induction putida and Pseudomonas fluorescens, as biotic elicitors in The inoculum suspensions were applied on both seedlings’ combination with WDS as abiotic elicitor, on Hyoscyamus radicles (1–2 mm length) and evenly within the 2 holes niger root and shoot growth, antioxidant enzymes (SOD, (1 cm depth) on the pot soil surface at a rate of 0.5 mL POX,CAT) activity, and the production of 2 main tropane per seedling using a syringe. Thereafter, 2 inoculated alkaloids, hyoscyamine and scopolamine. seedlings were immediately transplanted to a plastic pot (25 cm diameter and 30 cm deep) containing 8 kg of soil, 2. Materials and methods which had been sterilized by autoclaving at 105 °C for 2.1. Seed preparation and germination 60 min over 3 consecutive days. Untreated radicles and Seeds of Hyoscyamus niger were provided by the culture media served as controls (C). Sterilized broth Agricultural and Natural Resources Center in Esfahan, (free of bacterial population) was applied in the case of

Table 1. Multiple plant growth promoting activities of Pseudomonas putida-168 (PP) and Pseudomonas fluorescens-187 (PF) strains.

PGPR activities Ecological site of strains Pseudomonas strains P solubility Siderophore IAA production* HCN production ACC deaminase isolation (rhizosphere type) (µg mL–1) production (mg L–1 ) score activity 5 Wheat PP-168 - 2.25 17.921 + (high) (cv. Gaskozhen**) Wheat PF-187 438.38 1.25 5.152 - - (cv. Azar***) PGPR: Plant growth promoting rhizobacteria, * IAA: Indole-3-acetic acid (without presence of tryptophan), P (phosphorus), **Irrigated variety (hydrophyl), ***Dry land variety (xerophyl), HCN: Hydrogen cyanide, ACC: 1-aminocyclopropane-1-carboxylic acid. + and -: with and without activity, respectively.

351 GHORBANPOUR et al. / Turk J Biol

–1 the control plants. The experiment was conducted in a Chl a (mg g FW) = 11.75 × A 663 – 2.35 × A 645 –1 greenhouse located at the Faculty of Agricultural Science Chl b (mg g FW) = 18.61 × A 645 – 3.96 × A 663 at Tehran University (Karaj, Iran). During the experiment, The same leaf that was used to measure RWC was first the temperature ranged from 26 °C to 30 °C and relative used to measure leaf greenness using the Soil Plant Analysis humidity was between 65% and 75%. Plants were subjected Development (SPAD) chlorophyll meter (Minolta SPAD- to WDS treatments for 60 days, starting 45 days after 502 chlorophyll meter, Tokyo, Japan). planting. The field capacity (FC) of soil was determined 2.7. Proline content to be 12.5% using the pressure plate apparatus. The pot The proline content was quantified by the acid-ninhydrin surface was covered by sterile plastic beads to minimize procedure of Bates et al. (15). The leaf tissues (0.5 g) were evaporation and avoid contamination. Estimation of water ground with 3% sulfosalicylic acid (10 mL) and clarified depletion levels was done through weighing pots daily by centrifugation. Supernatant (2 mL) was mixed with (during morning hours). Monitoring of the soil moisture the same volume of acid-ninhydrin and acetic acid, the levels was conducted using a gravimetric method. The mixture was oven-incubated at 100 °C for 1 h, and the mechanical and chemical composition of the soil was as reaction was finished in an ice bath. The reaction mixture follows: 58.4% sand, 18.8% silt, 22.8% clay; total available was extracted with 4 mL of toluene using a vortex mixer N 0.12%, P 8.14 ppm, K 175 ppm. The study was set up as a for 15–20 s and absorbance was read at 520 nm. randomized complete block design (RCBD) with factorial experiments of 3 water deficit stress (WDS) levels at 30% 2.8. Antioxidant enzyme assays (W1), 60% (W2), and 90% (W3) water depletion of field A crude enzyme extract was prepared by homogenizing capacity and 2 PGPR strains along with controls (without 0.5 g of frozen root and leaf tissues in an extraction PGPR inoculation) in 3 replications. All the pots were kept buffer containing 0.5% Triton X-100 and 1% polyvinyl to the field capacity up to 45 days after planting. pyrrolidone in 100 mM potassium phosphate buffer (pH 7.0) using a chilled mortar and pestle. The homogenate 2.4. Plant growth measurements and analysis was centrifuged and the supernatant was used for the After 60 days of WDS, all pots were harvested at the full following enzyme assays. flowering stage. Plants were uprooted, washed carefully, and separated into fine roots (<1 mm diameter), coarse 2.8.1. Superoxide dismutase (SOD, EC 1.15.1.1) activity roots (≥1 mm diameter), , and stems for analysis. Total SOD activity was determined according to Leaves were counted and then total leaf area per plant Beauchamp and Fridovich (16). The reaction mixture −6 –1 –1 was measured using a LICOR Photoelectric Area Meter. contained 1.17 × 10 mol L riboflavin, 0.1 mol L −5 –1 −5 The plant materials were then shade dried, weighed with a methionine, 2 × 10 mol L KCN, and 5.6 × 10 mol –1 precision (0.0001 g) scale, finely powdered in an electronic L nitroblue tetrazolium (NBT) salt dissolved in 3 mL –1 blender, and kept in separate containers for tropane of 0.05 mol L sodium phosphate buffer (pH 7.8). Three alkaloid extraction. milliliters of the reaction medium was added to 1 mL of enzyme extract. The mixtures were illuminated in glass 2.5. Leaf relative water content (RWC) RWC was measured to evaluate plant water status on 3 tubes by 2 sets of Philips 40-W fluorescent tubes in leaves collected from each of 2 plants at 15, 30, 45, and 60 a single row. The absorbance was read at 560 nm in the days after stress (DAS). The 4th fully expanded leaf (from spectrophotometer against the blank. SOD activity is expressed in U mg−1 protein (U = change in 0.1 absorbance the top) was weighed immediately after cutting (FW), −1 −1 hydrated to full turgidity by floating in distilled water, h mg protein under assay conditions). kept at room temperature (22 °C) for 24 h to obtain turgid 2.8.2. Catalase (CAT, EC 1.11.1.6) activity weight (TW), and finally oven dried for 48 h at 70 °C to Total CAT activity was assayed according to the method measure dry weight (DW). RWC was calculated by the of Chandlee and Scandalios (17). The assay mixture following formula as described by Jeon et al. (13): RWC = contained 2.6 mL of 50 mmol L–1 potassium phosphate –1 [(FW − DW) / (TW − DW)] × 100. buffer (pH 7.0), 0.4 mL of 15 mmol L H2O2, and 0.04 mL 2.6. Chlorophyll pigment of enzyme extract. Changes in absorbance were read at 240 −1 Chlorophyll was extracted from the 4th fully expanded nm. The enzyme activity was expressed in U mg protein –1 –1 leaf from the top at the end of the experimental period. To (U = 1 mM of H2O2 reduction min mg protein). The extract chlorophyll, 50 mg of fresh leaf was homogenized enzyme protein was estimated by the method of Bradford in 5 mL of acetone (80% V/V). The extract was read at 645 (18) for all the enzymes. nm (chlorophyll a) and 663 nm (chlorophyll b) in a UV- 2.8.3. Peroxidase (POX, EC 1.11.1.7) activity 160 a spectrophotometer and chlorophyll contents were Total POX activity was determined by the method of Kumar calculated using the equations suggested by Lichtenthaler and Khan (19). The assay mixture for POX contained 2 mL (14): of 0.1 mol L–1 phosphate buffer (pH 6.8), 1 mL of 0.01 mol

352 GHORBANPOUR et al. / Turk J Biol

–1 –1 L pyrogallol, 1 mL of 0.005 mol L H2O2, and 0.5 mL of treatments and interactions, and lowest standard enzyme extract. The solution was incubated for 5 min at deviations (LSD) tests were used to compare means (P < 25 °C, after which the reaction was terminated by adding 0.05). Values obtained were expressed as mean ± standard –1 1 mL of 2.5 mol L H2SO4. The amount of purpurogallin deviation from 3 replications (n = 3) of each treatment. formed was determined by measuring the absorbance at 420 nm against a blank prepared by adding the extract 3. Results –1 after the addition of 2.5 mol L H2SO4 at zero time. The 3.1. Leaf parameters and growth variables −1 activity was expressed in U mg protein, with 1 U defined The results indicated that there were significant (P < –1 –1 as the change in the absorbance of 0.1 min mg protein. 0.01) interactions between WDS and the 2 Pseudomonas 2.9. Alkaloid extraction strains compared with untreated controls for most of the Root and shoot samples were air dried, ground into fine investigated traits. WDS resulted in a serious reduction in powder, and sieved with a laboratory mesh (size 30, mesh H. niger growth. Leaf numbers decreased with the increase opening 545 μm). A subsample of 2 g from each sample was in water stress levels, but PP- and PF-treated plants had added to an appropriate volume of CHCl3:MeOH:NH4OH lower reduction percentages compared to untreated 25%, (15:5:1), sonicated for 20 min, and then kept in a water control plants (C). Under low WDS (W1) conditions, the bath (40 °C) for 1 h. The subsequent sample preparation highest leaf number was recorded in PP-treated plants, and alkaloids extraction were based essentially on the followed by PF, and the lowest leaf number was recorded method described by Kamada (20). in the control treatment (C). At moderate (W2) and severe 2.10. Alkaloid analysis and quantification water stress (W3) levels, PP and PF strains caused the same Alkaloids extracted were identified by gas chromatography response, but PF-treated plants had a major advantage in (GC) and gas chromatography–mass spectrometry (GC– terms of leaf numbers in W3 conditions (Table 2). Leaf area MS) analysis. Gas chromatography analysis was performed variations had a similar trend as leaf number variations. using a GC system equipped with a flame ionization Leaf greenness values were significantly decreased in detector (FID) and HP-5MS capillary column (30 m × untreated plants exposed to WDS. Plant leaves in the 0.25 mm, film thickness 0.25 µm). Injector and detector W3PF treatment had the highest SPAD chlorophyll meter temperatures were set at 220 and 290 °C, respectively. The readings at the end of the experiment. column temperature was initially kept at 50 °C for 5 min, 3.2. Proline then gradually increased to 300 °C at a rate of 3 °C min–1, The PGPR strains varied greatly in their effect on proline and maintained for 3 min. The flow rate of helium was 0.8 content. The greatest accumulation of proline was found in mL min–1. Then 1 µL of extract was directly injected into PF-treated plants against severe WDS. In contrast, proline the gas chromatograph. Each extraction was replicated accumulation in PP-treated plants and in untreated control 3 times and the compound percentages are the means of plants was observed only up to the W2 treatment level and the 3 replicates. GC–MS analysis was carried out on an it later started to decline, particularly in the untreated Agilent 6890 gas chromatograph (Agilent Technologies, control plants (Table 2). Palo Alto, USA) fitted with a fused silica HP-5MS capillary 3.3. Chlorophyll column (30 m × 0.25 mm × 0.25 µm). Oven temperature Chlorophyll a, b, and total (a + b) chlorophyll contents was programmed from 50 °C to 285 °C at 3 °C min–1, dropped in untreated plants under severe WDS, but the and helium was used as carrier gas (0.8 mL min–1). Mass ratio between chlorophyll a and b (a/b) had an upward spectra were obtained in an Agilent 5973 system operating trend with increasing water stress. The results also in electron impact mode (EIMS) at 70 eV, coupled to an showed that chlorophyll b was more sensitive to WDS GC system. The identification of alkaloids was based on the than chlorophyll a. Inoculation with Pseudomonas strains comparison of their GC retention time and mass spectra significantly improved chlorophyll contents. In both strain (MS) data with their standard substances (HYO. HCl and treatments, the content of chlorophyll a and b increased SCO. HBr, Merck). The total tropane alkaloid (HYO + in response to water stress (P < 0.01), but the ratio of SCO) yield was quantified by both alkaloid content and chlorophyll a and b significantly decreased with increasing biomass production: Total alkaloid yield (mg plant–1) = WDS (Table 2). –1 Alkaloid content (% DW) × Plant dry weight (mg plant ). 3.4. Relative water content (RWC) 2.11. Statistical analysis Leaf RWC was significantly (P < 0.01) higher in the plants All analyses were performed based on a randomized experiencing PP and PF strains under all WDS conditions complete block design (RCBD) with factorial experiments. than their respective controls. RWC at 15 DAS was fairly The data were subjected to ANOVA and were analyzed high in most of the treatments. W1PP and W3C had the using SAS version 9.1 (CoHort Software). Probabilities highest (92.1%) and lowest (79.07%) values, respectively. of significance were used to test for significance among RWC for untreated control plants subjected to water stress

353 GHORBANPOUR et al. / Turk J Biol

Table 2. Mean values for leaf number, total leaf area, leaf greenness, proline, and chlorophyll content (mean ± SD, n = 3) of H. niger inoculated with Pseudomonas strains at different water deficit stress levels.

Leaf number Leaf area Proline Chlorophyll (mg g–1 FW) Treatment Leaf greenness (no. plant–1) (cm2 plant–1) (mg g–1 DW) a b a + b a/b W1PP 27.2 ± 0.71 354.1 ± 7.94 53.60 ± 1.02 0.27 ± 0.021 0.058 ± 0.001 0.102 ± 0.003 0.160 ± 0.004 0.57 ± 0.007 W1PF 24.3 ± 0.63 347.3 ± 6.43 51.55 ± 1.32 0.24 ± 0.013 0.056 ± 0.001 0.097 ± 0.002 0.153 ± 0.003 0.57 ± 0.012 W1C 22. 3 ± 0.61 301.7 ± 5.60 46.33 ± 2.19 0.19 ± 0.022 0.050 ± 0.003 0.091 ± 0.002 0.142 ± 0.003 0.55 ± 0.040 W2PP 21.2 ± 0.54 315.6 ± 7.56 56.43 ± 1.17 0.36 ± 0.014 0.062 ± 0.001 0.112 ± 0.004 0.174 ± 0.005 0.56 ± 0.006 W2PF 22.6 ± 0.77 329.3 ± 13.21 60.19 ± 1.26 0.39 ± 0.035 0.064 ± 0.003 0.116 ± 0.001 0.181 ± 0.003 0.55 ± 0.020 W2C 14.01 ± 0.68 256 ± 7.42 41.42 ± 1.59 0.25 ± 0.016 0.053 ± 0.002 0.080 ± .0003 0.113 ± 0.001 0.66 ± 0.050 W3PP 17.22 ± 1.32 273.1 ± 7.16 59.75 ± 1.21 0.34 ± 0.021 0.067 ± 0.002 0.122 ± 0.004 0.189 ± 0.007 0.54 ± 0.004 W3PF 19.50 ± 1.19 298.4 ± 10.2 63.17 ± 2.42 0.48 ± 0.031 0.076 ± 0.003 0.139 ± 0.0005 0.214 ± 0.003 0.55 ± 0.020 W3C 10.7 ± 0.63 179.1 ± 9.81 37.04 ± 1.37 0.14 ± 0.002 0.032 ± 0.003 0.045 ± 0.004 0.077 ± 0.006 0.71 ± 0.050 F WDS × PGPR 8.18** 36.06** 34.87** 7.88* 189.52** 159.43** 229.65** 14.26**

W1, W2, and W3: water deficit stress (WDS) at 30%, 60%, and 90% of water depletion from field capacity, respectively. PP, PF, and C: Pseudomonas fluorescens strain 187, P. putida strain 168, and control, respectively. *P < 0.05; **P < 0.01.

(W2C and W3C) started to decline at 30 DAS, sharply decreased by increasing WDS levels. The reduction ratio declined at 45 DAS, and then dropped to a very low value was very conspicuous in the control plants (2.2-fold (57%) during the final drought stress period. PP- and PF- reduction) compared to PP- and PF-treated plants (1.6- treated plants under the highest water supply (W1PP and and 1.3-fold reduction, respectively). The PP strain was W1PF) were found to have RWC in the range of 91%–92% more effective in promoting shoot weight when WDS (initial values) and showed a smaller decrease during the was applied at the W1 level. Similarly, when water stress WDS period, i.e. it decreased gradually within a narrow was applied at the W3 level, the maximum increases in range (Figure). shoot dry weight were observed in plants inoculated with 3.5. Root and shoot biomass the PF strain. Under W3 conditions, leaf number (Table There were significant variations (P < 0.01) in shoot (leaf 2) was 82.2% higher in PF-inoculated plants than in the and stem) dry weight of H. niger plants treated with PP controls, which is reflected in a 2.06-fold increase in shoot and PF when compared with the controls (Table 3). weight. WDS also led to a reduction in root mass as well Generally, the total shoot dry weight was significantly as to a reduction in shoot dry weight, but increased the 100 root to shoot ratio. Severe WDS (W3) was most intense for fine roots, i.e. roots less than 1 mm in diameter were 95 affected more severely (3.2-fold reduction) than coarse 90 W1PP roots (2.4-fold reduction) in the uninoculated control 85 W1PF plants compared to W1 conditions. Inoculation with these 80 W1C strains alleviated to some extent the effects of WDS on fine RCW (%) W2PP 75 W2PF root growth compared to the control plants (Table 3). 70 W2C 3.6. Antioxidant enzymes 65 W3PP W3PF There was a significant interaction between SOD, POX, 60 W3C and CAT activities in the roots and leaves of H. niger plants 55 under PGPR inoculation and WDS treatments. Different 15 30 45 60 Days a er stress (DAS) parts of the plant under different treatments showed varied enzyme activity (Table 4). The antioxidant enzyme SOD Figure. Leaf relative water content (RWC) variations of activity in root and leaf organs increased with increasing Hyoscyamus niger with inoculation of Pseudomonas putida-168 WDS in plants inoculated with both PP and PF strains. (PP) and P. fluorescens-187 (PF) strains compared with those of control (C) plants under water deficit stress levels; W1, W2, In the case of control plants, SOD activity increased and W3 (30%, 60%, and 90% water depletion of field capacity, with increasing WDS up to moderate water stress. The respectively) at 15, 30, 45, and 60 days after stress (DAS). Error highest level of WDS decreased the specific SOD activity, bars for all data represent standard deviation (±SD, n = 3) based as shown in Table 4. The highest SOD activity (23.821 U on least significant difference (LSD) (P < 0.05). mg–1 protein) was recorded in a W3PF-treated leaf sample

354 GHORBANPOUR et al. / Turk J Biol

Table 3. Biomass production (mean ± SD, n = 3) of H. niger inoculated with Pseudomonas strains at different water deficit stress levels.

Shoot dry weight (g plant–1) Root dry weight (g plant–1) Treatment Leaf Stem Total Fine root Coarse root Total W1PP 9.03 ± 0.114 7.37 ± 0.34 16.40 ± 0.13 7.21 ± 0.13 4.68 ± 0.18 11.89 ± 0.35 W1PF 8.60 ± 0.080 6.93 ± 0.66 15.53 ± 0.12 6.44 ± 0.17 4.89 ± 0.11 11.33 ± 0.26 W1C 6.73 ± 0.141 6.37 ± 0.34 13.10 ± 0.13 4.80 ± 0.248 3.65 ± 0.32 8.45 ± 0.55 W2PP 7.27 ± 0.107 5.70 ± 0.26 12.97 ± 0.12 5.20 ± 0.11 3.82 ± 0.16 9.02 ± 0.26 W2PF 7.67 ± 0.046 6.13 ± 0.36 13.80 ± 0.65 5.60 ± 0.13 4.39 ± 0.11 9.99 ± 0.20 W2C 4.80 ± 0.048 4.37 ± 0.12 9.17 ± 0.11 2.95 ± 0.055 2.27 ± 0.21 5.22 ± 0.28 W3PP 5.53 ± 0.121 4.40 ± 0.12 9.93 ± 0.23 3.99 ± 0.092 3.01 ± 0.091 7.00 ± 0.19 W3PF 6.40 ± 0.093 5.43 ± 0.12 11.83 ± 0.16 4.95 ± 0.18 3.12 ± 0.135 8.07 ± 0.24 W3C 2.90 ± 0.076 2.83 ± 0.14 5.73 ± 0.15 1.46 ± 0.045 1.51 ± 0.18 2.97 ± 0.17 F WDS × PGPR 21.40** 3.10* 13.68** 10.61** 5.40** 8.90**

W1, W2, and W3: water deficit stress at 30%, 60%, and 90% of water depletion from field capacity, respectively. PP, PF, and C: Pseudomonas fluorescens strain 187, P. putida strain 168, and control, respectively. *P < 0.05; **P < 0.01. and the lowest activity (6.97 U mg–1 protein) was recorded the leaves of untreated control plants under severe WDS in the W1C root sample. The CAT activity in root and compared to W1 (Table 4). leaf samples increased with increasing WDS only in PF- 3.7. Tropane alkaloid content and yield treated plants, but plants treated with the PP strain and In Pseudomonas strain-treated and uninoculated control control uninoculated plants showed reduced activity of plants, the SCO content of roots increased significantly this enzyme under WDS conditions. A gradual increase with increasing WDS up to W2 treatment and later started was observed in leaf CAT activity under 60% FC with PP- to decline, except for PF-treated plants, which kept a treated (W2PP) plants in comparison with the controls. continuously upward trend (Table 5). The largest root SCO Increasing the WDS caused a marked increase in total content was observed in the PF-treated plants under W3 POX activity of both roots and leaves in PGPR-treated conditions. There was no significant interaction among and control plants, particularly in the PF-treated plants the treatments in terms of root HYO content, but it was under severe WDS. Among all antioxidant activities, the influenced by PGPR and WDS separately. The maximum maximum reduction was observed in CAT activity in root HYO content was seen in the W3 treatment, while

Table 4. Superoxide dismutase (SOD), catalase (CAT), and peroxidase (POX) activities of roots and leaves in H. niger plants inoculated with Pseudomonas strains at different water deficit stress levels (mean ± SD, n = 3).

Antioxidant enzyme activity (U mg–1 protein) Treatment Root enzymes Leaf enzymes SOD CAT POX SOD CAT POX W1PP 7.45 ± 0.086 2.183 ± 0.074 3.630 ± 0.192 12.887 ± 0.149 2.861 ± 0.088 5.507 ± 0.281 W1PF 7.22 ± 0.041 1.983 ± 0.090 2.587 ± 0.134 11.304 ± 0.056 2.967 ± 0.095 4.40 ± 0.341 W1C 6.97 ± 0.034 1.036 ± 0.045 2.065 ± 0.082 8.954 ± 0.244 2.550 ± 0.012 2.113 ± 0.121 W2PP 9.29 ± 0.112 1.250 ± 0.237 5.493 ± 0.144 14.298 ± 0.132 3.119 ± 0.028 7.050 ± 0.107 W2PF 10.33 ± 0.186 2.762 ± 0.157 4.825 ± 0.041 17.375 ± 0.053 3.217 ± 0.086 6.40 ± 0.182 W2C 8.00 ± 0.047 0.830 ± 0.098 2.435 ± 0.040 11.019 ± 0.135 0.933 ± 0.145 2.207 ± 0.105 W3PP 13.89 ± 0.124 0.945 ± 0.132 6.729 ± 0.034 19.615 ± 0.067 1.094 ± 0.078 9.37 ± 0.163 W3PF 15.02 ± 0.145 3.784 ± 0.141 8.354 ± 0.229 23.821 ± 0.201 3.337 ± 0.097 13.12 ± 0.041 W3C 7.27 ± 0.196 0.465 ± 0.056 2.478 ± 0.098 9.849 ± 0.223 0.2 10 ± 0.057 2.735 ± 0.101 F WDS × PGPR 13.74** 21.57* 16.38** 11.09** 4.06* 9.37**

W1, W2, and W3: water deficit stress at 30%, 60%, and 90% of water depletion from field capacity, respectively. PP, PF, and C: Pseudomonas fluorescens strain 187, P. putida strain 168, and control, respectively. *P < 0.05; **P < 0.01.

355 GHORBANPOUR et al. / Turk J Biol

Table 5. Root and shoot alkaloids (HYO and SCO) content (mean ± SD, n = 3) of H. niger inoculated with Pseudomonas strains at different water deficit stress levels.

Root alkaloid content (%DW) Shoot alkaloid content (%DW) Treatment HYO SCO HYO SCO W1PP 0.351 ± 0.005 0.088 ± 0.005 0.888 ± 0.006 0.362 ± 0.005 W1PF 0.334 ± 0.005 0.080 ± 0.004 0.875 ± 0.006 0.350 ± 0.007 W1C 0.270 ± 0.008 0.058 ± 0.012 0.812 ± 0.009 0.270 ± 0.01 W2PP 0.363 ± 0.005 0.106 ± 0.002 0.905 ± 0.005 0.377 ± 0.004 W2PF 0.369 ± 0.008 0.109 ± 0.006 0.930 ± 0.005 0.378 ± 0.004 W2C 0.283 ± 0.01 0.072 ± 0.013 0.835 ± 0.01 0.287 ± 0.008 W3PP 0.384 ± 0.005 0.096 ± 0.003 0.930 ± 0.005 0.350 ± 0.004 W3PF 0.407 ± 0.006 0.133 ± 0.006 0.960 ± 0.005 0.397 ± 0.004 W3C 0.299 ± 0.009 0.041 ± 0.01 0.854 ± 0.01 0.224 ± 0.007 F WDS × PGPR 2.55 n.s. 0.12 n.s. 5.05** 7.88**

W1, W2, and W3: water deficit stress at 30%, 60%, and 90% of water depletion from field capacity, PP, PF, and C: Pseudomonas putida-168, P. fluorescens-187 strains, and control, respectively. *P < 0.05; **P < 0.01; n.s. P > 0.05. the effects of PP and PF strains were identical. In shoots, however, the percentage reductions in PP- and PF-treated however, HYO content significantly increased with plants were lower than those in the uninoculated controls. increasing WDS in all employed treatments. The results also Shoot SCO yield also decreased with increasing WDS in showed that HYO content of shoots under W3 conditions PP-treated and control plants, but was unchanged in PF- for PF- and PP-inoculated plants were almost 12.4% and treated plants. The largest total alkaloid (HYO + SCO) 8.9% higher than that of control plants, respectively. SCO yield was seen in PP-treated plants under W1 conditions content of shoots in all employed treatments had the same mainly because of lower growth parameter reductions in changes as roots, and mildly increased with increasing comparison with the other treatments (Table 6). WDS only in PF-treated plants (Table 5). It seems that inoculation of H. niger plants with PF promoted HYO 4. Discussion and SCO accumulation in both root and shoot organs. Rhizobacteria, including fluorescent pseudomonads, have Shoot HYO yield decreased with increasing WDS in both substantial effects on plant growth, particularly under stress Pseudomonas-treated and uninoculated control plants; conditions, and play an important role in plant physiology

Table 6. Mean values for the alkaloids (HYO and SCO) yield in root and shoot (mean ± SD, n = 3) of H. niger inoculated with Pseudomonas strains at different water deficit stress levels.

Root alkaloid yield (mg plant–1) Shoot alkaloid yield (mg plant–1) Total alkaloids Treatment HYO SCO HYO SCO yield (mg plant–1) W1PP 4.172 ± 0.115 1.046 ± 0.056 14.572 ± 0.149 5.921 ± 0.095 25.711 ± 0.40 W1PF 3.790 ± 0.105 0.907 ± 0.042 13.591 ± 0.144 5.421 ± 0.088 23.709 ± 0.34 W1C 2.310 ± 0.145 0.492 ± 0.092 10.634 ± 0.192 3.524 ± 0.098 16.960 ± 0.43 W2PP 3.286 ± 0.097 0.953 ± 0.037 11.740 ± 0.067 4.872 ± 0.040 20.851 ± 0.19 W2PF 3.696 ± 0.111 1.094 ± 0.044 12.828 ± 0.041 5.192 ± 0.012 22.811 ± 0.09 W2C 1.487 ± 0.078 0.377 ± 0.057 7.660 ± 0.147 2.616 ± 0.056 12.140 ± 0.24 W3PP 2.690 ± 0.057 0.668 ± 0.032 9.244 ± 0.141 3.472 ± 0.082 16.074 ± 0.30 W3PF 3.301 ± 0.096 1.046 ± 0.044 11.351 ± 0.026 4.682 ± 0.008 20.398 ± 0.09 W3C 0.892 ± 0.056 0.123 ± 0.043 4.899 ± 0.090 1.281 ± 0.045 7.194 ± 0.17 F WDS × PGPR 11.09** 4.06* 13.74** 21.57** 24.34**

W1, W2, and W3: water deficit stress (WDS) at 30%, 60%, and 90% of water depletion from field capacity, respectively. PP, PF, and C:P. putida-168, P. fluorescens-187 strains, and control, respectively.*P < 0.05; **P < 0.01.

356 GHORBANPOUR et al. / Turk J Biol by a combination of direct and indirect mechanisms (21). root branching (30). Marcelo et al. (22) demonstrated In our study, PGPR inoculation had positive effects on that common bean (Phaseolus vulgaris L.) treated with root and shoot growth indexes such as leaf number, leaf Azospirillum brasilense Cd (N2-fixing and PGPR) had area, and leaf greenness both in the presence and absence enhanced root length and area compared to uninoculated of WDS. Moreover, root inoculation of H. niger with these controls, resulting in root systems with longer and thinner PGPR decreased the severe negative effects of WDS on fine roots. Plants with very fine roots are more effective for root growth. This effect could be attributed to the ability of water and mineral uptake due to higher root specific PP and PF to release indole-3-acetic acid (IAA). Similarly, surface area. Our results indicated that the PF strain had growth promotion of many plants with inoculation of higher efficiency than the PP strain in plants growing PGPR has been reported previously (22,23). It has been under moderate (W2) and severe (W3) WDS conditions. suggested that direct mechanisms of PGPR involve Strain PF (with a strong phosphorous solubilizing activity) secretion of plant growth regulators (auxins, cytokinins, was isolated from rainfed (dry land farming) wheat and gibberellins), which enhance various stages of plant rhizosphere, where water is restricted and dry periods growth or synthesize enzymes that modulate plant often take place. This may explain the superiority of PF growth and development (24). In the present study, the under a limited water supply compared to PP (which has increase in root dry weight compared to shoot in both no phosphorous solubilizing activity), which was isolated PP- and PF-treated plants under WDS treatments could from irrigated wheat rhizosphere (Table 1). Such results be associated with multiple plant growth promoting traits were also in accordance with a previous report by Mayaka such as phosphorus solubility, siderophore and hydrogen (31). Although ACC deaminase activity was not observed cyanide (HCN) production, auxin secretion, and ACC in PF characteristics (Table 1), this strain improved root and (1-aminocyclopropane-1-carboxylic acid) deaminase shoot growth compared to PP and uninoculated control activity of PP and PF (Table 1), which change the assimilate plants under severe WDS. Several studies have supported allocation patterns in plants and affect the growth patterns the beneficial effects of ACC deaminase activity of PGPR in roots. As a result, H. niger root systems were larger and on plants growing under stress conditions (21). This may more branched, which was in agreement with findings be attributed to other bacterial abilities. It is obvious that reported by Potters et al. (25). Moreover, solubilization of ACC deaminase activity is not the only factor responsible inorganic phosphate, mineralization of organic phosphate, for root growth enhancement. ACC deaminase activity improved nutrient uptake, inhibition of plant ethylene might have produced better root growth in the initial synthesis, and enhanced stress resistance are modulated by stages of crop growth in stress conditions (32), whereas in PGPR as direct mechanisms (26). In indirect mechanisms, the present study water stress started at 45 DAS. In our secondary bacterial metabolites are involved such as HCN study, WDS reduced the contents of chlorophyll a and b. and siderophore production that chelate iron and make it A reduction in chlorophyll content has also been reported available to the plant root (21). It was recently reported in certain plant species exposed to drought stress, such as that inoculation of wheat seedlings with Mycobacterium periwinkle (33). Inoculation of H. niger plants with PGPR phlei significantly stimulated shoot growth (up to 32%), partially eliminated the deleterious water stress effects on root growth (up to 6%), and dry matter contents (up to growth and chlorophyll content, as was evident from the 52%) under saline conditions through its ability to produce data documented in Tables 2 and 3. Application of PGPR different biologically active compounds, such as cell wall- on pea (Pisum sativum L.) was found to be very effective degrading enzymes and the phytohormone auxin (27). in decreasing the drought stress effects on the chlorophyll WDS, like many abiotic stresses, causes pronounced content (34). In research by Karakurt et al. (35) the effects effects on RWC, chlorophyll, and proline content. WDS of 4 plant growth promoting rhizobacteria, alone and in decreased RWC in the leaves of H. niger plants. The combination, on growth and chemical characteristics of RWC values of pseudomonas-treated plants were higher sour cherry was studied, and it was reported that all the than respective uninoculated control plants. This may tested bacterial strains had a great potential to increase be associated with the hydraulic nature of branch root plant vegetative growth and indirectly affect chemical junctions, which facilitate the radial flow of water, as characteristics. Our results in this case are in accordance previously reported by Kothari et al. (28). Yuwono et al. with findings reported by Jaleel et al. (23) in Catharantus (29) reported that root proliferation enhancement and roseus. Our findings suggested that using native PGPR enhanced water uptake in inoculated drought-stressed rice strains to induce and enhance pigment biosynthesis could plants may be induced by IAA. The advantageous effects be a biological strategy for improving drought tolerance in of PGPR and common adaptation mechanisms of plants plants growing under water stress conditions. Rhizosphere exposed to WDS are always mutually related to exceptional and plant dependent mechanisms have been proposed for changes in root morphology such as root dry weight and the stress tolerance mediated by PGPR (36).

357 GHORBANPOUR et al. / Turk J Biol

Studies have shown that WDS is a major environmental CAT, which is localized in peroxisomes, dismutates H2O2 factor limiting the productivity of plants (biomass into H2O and O2 (41). According to our results, although accumulation) and may cause damage to plant tissues, the activities of SOD and POX of roots and leaves in PGPR- especially roots, through the formation of ROS such treated plants were upregulated by WDS, CAT activity -2 - as H2O2, O and OH , due to high susceptibility of root decreased in all treatments, except for in PF-inoculated meristem activity to ROS (9). In order to decrease the plants (Table 4). The decline in CAT activity is regarded deleterious effects of ROS, antioxidant promoting systems as a common response to many stresses. The reduction of are required, such as PGPR application. Plants have CAT activity is supposedly due to the inhibition of enzyme developed physiological and biochemical mechanisms to synthesis or change in the assembly of enzyme subunits respond and adapt to this stress in order to survive. The under stress conditions. It may also be associated with carbon/nutrient balance (CNB) and growth differentiation degradation caused by induced peroxisomal proteases or balance (GDB) hypotheses predict a trade-off between may be due to the photo-inactivation of the enzyme (44). growth and defense systems. Because WDS reduces Our results are in agreement with the findings reported plant growth, the carbon fixed during photosynthesis by Kohler et al. (43) in lettuce plants, which showed that can be used for the production of secondary metabolites the greater activity of antioxidant CAT and accumulation (37). Although WDS is the major limiting factor on crop of under severe drought conditions were recorded when plant growth and biomass production, enhancement inoculated with PGPR, Pseudomonas mendocina, and of secondary plant products, solute accumulation, and arbuscular mycorrhizal fungi. enzyme activities are considered positive effects of limited It is suggested that the overexpression of SOD, if accompanied by enhanced H O scavenging mechanisms water supply in medicinal plants (38). 2 2 Proline accumulation is a very common response like CAT and POX activities, has been considered an in plants exposed to WDS; it contributes to osmotic important antidrought mechanism to cope with oxidative stress during WDS conditions (43). Generally, SOD and adjustment and protects the structure of macromolecules POX in roots and leaves showed simultaneous induction and cell membranes during WDS (39). Meloni et al. (40) and decline, which may be due to their co-regulation, suggest that amino acids such as proline acts as an organic which agrees with the finding reported by Shigeoka et al. nitrogen reserve in plant metabolism, as a readily available (45). Plants inoculated with PF and PP strains were more source of energy, and as possible precursors of alkaloid hydrated than the control untreated plants. These results formation. This could explain why the plants inoculated demonstrated that the PGPR treatment influenced the with the PF strain produced higher contents of tropane extent of WDS and that PF efficiently protected the host alkaloids. -2 plants against the detrimental effects of WDS. Likewise, our WDS is known to increase O production in results indicated a significant role of PGPR, particularly in chloroplasts. SOD is an enzyme that catalyzes the the application of PF, providing a protective mechanism by conversion of the O-2 to O and H O (41). Enhanced SOD 2 2 2 scavenging ROS and increasing the activities of SOD and activity of roots and leaves under severe WDS conditions CAT against drought-dependent oxidative damage. for PGPR-treated plants may be interpreted as a direct The use of elicitors is an effective means employed to -2 response to augmented O generation, particularly in increase the production of important alkaloids. PGPR chloroplast compartments. In our study, SOD activity and osmotic stresses are classified as biotic and abiotic of roots and leaves showed a significant increase with secondary metabolites elicitors in medicinal plants (46). increasing WDS and PGPR application. The important In our study, rhizobacteria have ability to produce growth point here is a decrease in SOD activity in both roots and regulators such as IAA (Table 1), which could act as leaves of control plants under severe WDS, which may elicitors on tropane alkaloid biosynthesis under WDS, reflect the low ROS scavenging capacity and increased resulting in raising alkaloid yield and content. According damage to plant parts under this condition. to our results, PP-treated plants under W1 conditions POX showed an increase in activity in response to had a higher proportion of fine roots compared to other WDS in root and leaf parts of both PGPR-treated and treatments, resulting in high HYO and SCO yield in the control plants. This enzyme is involved in the scavenging roots and shoots. Nakanishi et al. (47) found that root of H2O2, growth, and developmental processes (42). Thus, secondary growth is a significant factor determining our results show that drought-related oxidative stress tropane alkaloid composition, which varied based on root upregulated the activity of POX in H. niger root and leaf diameter. The plant growth promoting properties of PGPR organs. This might be an important protection mechanism could be the driving force for the alkaloid yield increment in H. niger plants against the excessive increase of H2O2 in this study. WDS had also positive effects (but less than during WDS. These results are also consistent with those PGPR) on alkaloid content of plant roots and shoots. reported by Kohler et al. (43). Increases in free amino acids, soluble proteins, and soluble

358 GHORBANPOUR et al. / Turk J Biol carbohydrates are among the factors contributing to of these alkaloids, but retarded the growth parameters, higher alkaloid contents in plants experiencing WDS (48). resulting in low alkaloid yield. Moreover, plants treated However, it significantly reduced plant biomass, which is a with the PP strain had the highest alkaloid yield under key determinant of alkaloid yield per plant. In the current low WDS conditions, whereas under moderate and severe study, shoots showed higher alkaloid accumulation than WDS, PF was the effective strain. Therefore, application of roots. It is well established that the root is the location of suitable PGPR strains should be based on multiple plant tropane alkaloid biosynthesis in Solanaceae family plants, growth promoting characteristics and their ecological but they may be transported to the aboveground parts of adaptation with respect to the abiotic stress of the host the plant (49). plant. Integrative use of effective PGPR strains (biotic The results of this study suggest that H. niger plants elicitors) and abiotic elicitors such as WDS appears to with an inoculation of PF under moderate WDS (W2), in be an encouraging new method and ecofriendly strategy addition to having appropriate amounts of each alkaloid for increasing tropane alkaloid yield and quality in H. content and yield, also have the largest value of SCO, niger plants. In the future, we will conduct studies on which is the indicator of tropane alkaloid quality. Thus, correlations between the tropane alkaloid biosynthesis inoculation of H. niger roots with PF strain not only and the activities of putrescine N-methyltransferase and alleviated the deleterious stress effects on plant growth hyoscyamine 6β-hydroxylase, enzymes that are involved to some extent, it also improved the growth parameters in the biosynthesis of tropane alkaloids, with inoculation under WDS and increased elicitation of tropane alkaloid of PGPR under WDS conditions. production. Our results suggest that inoculation of H. niger Acknowledgments plants with PP and PF strains stimulated the activities of The authors are grateful to the agronomy and plant antioxidant enzymes, increased proline accumulation, breeding department of Tehran University and the institute and remarkably improved the alkaloid content and yield of medicinal plants (ACECR), Karaj, Iran, for supporting of root and shoot organs. WDS improved the content this study.

References

1. Pitta ASI, Spollansky TC, Giulietti AM. The influence of 10. Simova-Stoilova L, Demirevska K, Petrova T et al. Antioxidative different biotic and abiotic elicitors on the production and protection and proteolytic activity in tolerant and sensitive profile of tropane alkaloids in hairy root cultures ofBrugmansia wheat (Triticum aestivum L.) varieties subjected to long-term candida. Enzyme Microb Tech 26: 252–258, 2000. field drought. Plant Growth Regul 58: 107–117, 2009. 2. Hashimoto T, Yamada Y. Hyoscamine 6β-hydroxylase, a 11. Dobbelaere S, Vanderleyden J, Yaacov Y et al. Plant growth- 2-oxoglutarate-dependent dioxygenase, in alkaloid-producing promoting effects of diazotrophs in the rhizosphere. Crit Rev root cultures. Plant Physiol 81: 619–625, 1986. Plant Sci 22: 107–149, 2003. 3. Oksman CKM, Hiltunen R. Transgenic crops for improved 12. Wu QS, Xi RX, Zou YN. Improved soil structure and citrus pharmaceutical products. Field Crop Res 45: 57–69, 1996. growth after inoculation with three Arbuscular mycorrhizal 4. Willaman JJ, Li HL. Alkaloid bearing plants and their contained fungi under drought stress. Eur J Soil Biol 44: 122–128, 2008. alkaloids. J Nat Prod 30: 1–4, 1970. 13. Jeon MW, Ali MB, Hahn EJ et al. Photosynthetic pigments, 5. Suzuki K, Yamada Y, Hashimoto T. Expression of Atropa morphology and leaf gas exchange during ex-vitro belladonna putrescine N-methyltransferase gene in root acclimatization of micropropagated CAM Doritaenopsis pericycle. Plant Cell Physiol 40: 289–297, 1999. plantlets under relative humidity and air temperature. Environ 6. Sanchez BJ, Trinitario M, Ferradez M et al. Variations in water Exp Bot 55: 183–194, 2006. status, gas exchange, and growth in Rosmarinus officinalis 14. Lichtenthaler HK. Chlorophylls and carotenoids; pigments of plants infected with Glomus deserticola under drought photosynthetic biomembranes. Method Enzymol 148: 350– conditions. J Plant Physiol 161: 675–682, 2004. 382, 1987. 7. Marulanda A, Porcel R, Barea JM et al. Drought tolerance and antioxidant activities in lavender plants colonized by native 15. Bates IS, Waldren RP, Teare JD. Rapid determination of free drought-tolerant or drought-sensitive Glomus species. Microb proline for water stress studies. Plant Soil 39: 205–207, 1973. Ecol 54: 543–552, 2007. 16. Beauchamp C, Fridovich I. Superoxide dismutase: improved 8. Imlay JA. Pathways of oxidative damage. Annu Rev Microbiol assays and an assay applicable to acrylamide gels. Anal 57: 395–418, 2003. Biochem 44: 276–287, 1971. 9. Foreman J, Demidchik V, Bothwell JHF et al. Reactive oxygen 17. Chandlee JM, Scandalios JG. Analysis of variants affecting the species produced by NADPH oxidase regulate plant cell catalase development program in maize scutellum. Theor Appl growth. Nature 422: 442–446, 2003. Genet 69: 71–77, 1984.

359 GHORBANPOUR et al. / Turk J Biol

18. Bradford MM. A rapid and sensitive method for the 34. Arshad M, Shaharoona B, Mahmood T. Inoculation with quantification of microgram quantities of protein utilizing the Pseudomonas spp. containing ACC-deaminase partially principle of protein dye binding. Anal Biochem 72: 248–253, eliminates the effects of drought stress on growth, yield and 1976. ripening of pea (Pisum sativum L.). Pedosphere 18: 611–620, 2008. 19. Kumar KB, Khan PA. Peroxidase and polyphenol oxidase in excised ragi (Eleusine coracana cv. PR 202) leaves during 35. Karakurt H, Kotan R, Dadasoglu F et al. Effects of plant growth senescence. Ind J Exp Bot 20: 412–416, 1982. promoting rhizobacteria on fruit set, pomological and chemical characteristics, color values, and vegetative growth of sour 20. Kamada H, Okamura N, Satake M et al. Alkaloid production cherry (Prunus cerasus cv. Kutahya). Turk J Biol 35: 283–291, by hairy root cultures in . Plant Cell Rep 5: 2011. 239–242, 1986. 36. Christian D, Tanja W, Folkard A. Plant–rhizobacteria 21. Glick BR, Todorovic B, Czamy J et al. Promotion of plant interactions alleviate abiotic stress conditions. Plant Cell growth by bacterial ACC deaminase. Crit Rev Plant Sci 26: Environ 32: 1682–1694, 2009. 227–242, 2007. 37. Turtola S, Manninen A, Rikala R et al. Drought stress alters the 22. Marcelo AG, Saul B, Okon Y et al. Effects of Azospirillum concentration of wood terpenoids in Scots pine and Norway brasilense on root morphology of common bean (Phaseolus spruce seedlings. J Chem Ecol 29: 1981–1995, 2003. vulgaris L.) under different water regimes. Biol Fert Soils 32: 38. Neelam S, Farooq AHA, Rajender S. Effect of drought stress 259–264, 2000. on growth and essential oil metabolism in lemongrasses. New 23. Jaleel CA, Manivannan P, Sankar B et al. Pseudomonas Phytol 128: 173–179, 1994. fluorescens enhances biomass yield and ajmalicine production 39. Prado FE, Boero C, Gallardo M et al. Effect of NaCl on in Catharanthus roseus under water deficit stress. Colloid germination, growth, and soluble sugar content in Chenopodium Surface B 60: 7–11, 2007. quinoa wild seeds. Bot Bull Acad Sinica 41: 27–34, 2000. 24. Gray EJ, Smith DL. Intracellular and extracellular PGPR, 40. Meloni DA, Oliva MA, Ruiz HA et al. Contribution of proline commonalities and distinctions in the plant–bacterium and inorganic solutes to osmotic adjustment in cotton under signalling processes. Soil Biol Biochem 37: 395–412, 2005. salt stress. J Plant Nutr 24: 599–612, 2001. 41. Hafsi C, Romero-Puertas MC, del Río LA et al. Antioxidative 25. Potters G, Pasternak TP, Guisez Y et al. Stress-induced response of Hordeum maritimum L. to potassium deficiency. morphogenic responses: growing out of trouble? Trends Plant Acta Physiol Plant 33: 193–202, 2011. Sci 12: 98–105, 2007. 42. Quiroga M, Guerrero C, Botella MA et al. A tomato peroxidase 26. Mehboob I, Naveed M, Ahmad Zahir Z. Rhizobial association involved in the synthesis of lignin and suberin. Plant Physiol with non-legumes: mechanisms and applications. Crit Rev 122: 1119–1127, 2000. Plant Sci 28: 432–456, 2009. 43. Kohler J, Caravaca F, Carrasco L et al. Contribution of 27. Dilfuza Egamberdieva D. Colonization of Mycobacterium phlei Pseudomonas mendocina and Glomus intraradices to aggregates in the rhizosphere of wheat grown under saline conditions. stabilisation and promotion of biological properties in Turk J Biol 36: 487–492, 2012. rhizosphere soil of lettuce plants under field conditions. Soil 28. Kothari SK, Marchner H, George E. Effect of VA mycorrhizal Use Manage 22: 298–304, 2006. fungi and rhizosphere microorganisms on root and shoot 44. Liu JR, Chen GF, Shi HN et al. Enhanced antioxidant bioactivity morphology, growth and water relations in maize. New Phytol of Salvia miltiorrhiza (Danshen) products prepared using 116: 303–311, 1990. nanotechnology. Phytomedicine 15: 23–30, 2008. 29. Yuwono T, Handayani D, Soedarsono J. The role of 45. Shigeoka S, Ishikawa T, Tamoi M et al. Regulation and function osmotolerant rhizobacteria in rice growth under different of ascorbate peroxidase isoenzymes. J Exp Bot 53: 1305–1319, drought conditions. Aust J Agr Res 56: 715–721, 2005. 2002. 46. Jaleel CA, Gopi R, Gomathinayagam M et al. Traditional and 30. Okon Y, Vanderleyden J. Root-associated Azospirillum species non-traditional plant growth regulators alter phytochemical can stimulate plants. ASM News 63: 366–370, 1997. constituents in Catharanthus roseus. Process Biochem 44: 205– 31. Mayaka S, Tsipora T, Bernard R et al. Plant growth-promoting 209, 2009. bacteria that confer resistance to water stress in tomatoes and 47. Nakanishi F, Sasaki K, Shimomura K. Kinetics of littorine peppers. Plant Sci 166: 525–530, 2004. content in various developing stages of regenerates of Atropa 32. Patten CL, Glick BR. Role of Pseudomonas putida and indole belladonna. Plant Cell Rep 19: 1021–1026, 2000. acetic acid in development of the host plant root system. Appl 48. Mattson WJ, Haack RA. The role of drought in outbreaks of Environ Microb 68: 3795–3801, 2002. plant-eating insects. BioScience 37: 110–118, 1987. 33. Jaleel CA, Gopi R, Panneerselvam R. Growth and photosynthetic 49. Zárate R, Hermosin B, Cantos M et al. Tropane alkaloid pigments responses of two varieties of Catharanthus roseus to distribution in Atropa baetica plants. J Chem Ecol 23: 2059– triadimefon treatment. CR Biol 331: 272–277, 2008. 2066, 1997.

360