Journal of
Horticulture and Forestry

  • Abbreviation: J. Hortic. For.
  • Language: English
  • ISSN: 2006-9782
  • DOI: 10.5897/JHF
  • Start Year: 2009
  • Published Articles: 273

Full Length Research Paper

Tolerance of bio-fertilized Delonix regia seedlings to irrigation intervals

Amira Sh. Soliman
  • Amira Sh. Soliman
  • Natural Resources Department, Institute of African Research and Studies, Cairo University, Giza, Egypt.
  • Google Scholar
Ebtsam M. Morsy
  • Ebtsam M. Morsy
  • Agriculture Microbiology Department, Soils, Water and Environment Research Institute, Agricultural Research Centre, Giza, Egypt.
  • Google Scholar
Osama N. Massoud
  • Osama N. Massoud
  • Agriculture Microbiology Department, Soils, Water and Environment Research Institute, Agricultural Research Centre, Giza, Egypt.
  • Google Scholar


  •  Received: 28 November 2014
  •  Accepted: 27 January 2015
  •  Published: 01 March 2015

 ABSTRACT

This work aims to investigate the effect of different bio-fertilizers (Arbascular mycorrhizae fungi, Azotobacter chroorcoccum, yeast strains and mixture of all inoculum) and irrigation intervals (3, 6 or 12 days) on the growth and chemical composition of Delonix regia seedlings grown in sandy soil. Pot experiments were conducted using a randomized complete blocks design with three replicates during two successive seasons of 2013 and 2014. The results indicated that dual bio-fertilizers led to significant increase in growth characters  (plant height, root length, number of branches/plant, total fresh and dry weights/plant), microbial populations and AM fungi colonization (%), enzymatic activities, chemical composition (plant pigments, total carbohydrates, proline content, N, P, K) besides antioxidant enzymes such as catalase (CAT),and peroxidase (POD) compared to the un-inoculated seedlings (as control) at the recommended dose of NPK chemical fertilizers under the same conditions. Generally, these results undoubtedly confirm that dual bio-fertilizers could replace the use of chemical fertilizers and consequently improve the quality and quantity of D. regia.

 

Key words: Delonix regia, Arbascular mycorrhizae fungi, Azotobacter chroorcoccum, yeast strains - growth characters, chemical composition.


 INTRODUCTION

Lack of fresh water resources for agriculture is the most important problem facing many countries in arid and semi-arid regions of Africa, such as Egypt. Thus there is a need to look for alternative methods to balance sustenance with demand (Wolters et al., 2013).
 
Using drought-tolerant trees in dry regions is one of many ways used to solve this problem. Delonix regia is one of the most important and common drought tree species in Egypt which also tolerates a wide variety of soils and conditions but needs to be well-watered until it gets established. The genus name is derived from the Greek words delos (meaning conspicuous) and onyx (meaning claw) referring to the appearance of the spectacular flowers. The tree is commonly cultivated in the tropics and subtropics, including Madagascar (Menninger,  1962).   It    plays  a  key  role  in  regulating
 
climate, resisting wind, sand, conserving water and soil (Du Puy et al., 2002). It is an ornamental tree found in streets and parks. It is fast-growing and develops an umbrella-shaped crown, making it a valuable shade tree. The wood is widely used as firewood and for making fence posts. It has an antioxidant potential (Auudy et al., 2003) and its seeds contain gum that may be used in food and textile industries. Its dried seeds can also be used as a binder in the manufacturing of tablets (e.g. Paracetamol). Its bark has medicinal properties (Little and Wadsworth, 1964; Webb et al., 1984).
 
Numerous studies have found that plants have mecha-nisms to cope with drought stress; they will become more tolerant to drought when associated with different soil microorganisms (Soliman, 2008; Aroca and Ruiz-Lozano, 2009). Beneficial microorganisms are a tool that enhances yield, plant growth and nutrient uptake under various environmental conditions such as salinity, drought and low fertility supply. Some endomycorrhizal fungi (Arbuscular mycorrhizal fungi) have been proven to improve drought stress; they colonize bio-trophically the root cortex and develop an extra-metrical mycelium that helps the plants to acquire mineral nutrients from the soil particularly those, which are immobile. They can under drought conditions stimulate growth-regulating substances, increase photosynthesis, improve osmotic adjustment, optimize hormonal balance and enhance water uptake (Colla et al., 2007).
 
Some yeast species (Saccharomyces cerevisiae and Rhodotorula mucilaginosa) and Azotobacter spp. have evolved different strategies to adapt with the changes in their environment. They can combat high osmolarity by enhancing transcription (Treuner-lange et al., 1997) or by the presence of some stress enzymes like catalases and peroxidases or organic and inorganic compounds.
 
Therefore, this study aims to investigate the effect of specific bio-fertilizers on increasing the drought resistance of D. regia seedlings under irrigation intervals.


 MATERIALS AND METHODS

The present study was carried out at the Experimental Laboratories of the Natural Resources Department, Institute of African Research and Studies, Cairo University, and at the Microbiology Department, Soils, Water and Environment Institute (SWERI), Agricultural Research Center, Giza, Egypt, during the two successive seasons of 2013 and 2014.
 
Plant material
 
Seeds of D. regia (Bojer ex Hook.) Raf. were obtained from the Faculty of Agriculture, Giza, Egypt. They were soaked in hot water (90°C) for 10 s followed by 24-h imbibitions, to accelerate germination (Millat and Mustafa, 1989). On the first of June, the seeds were then sown in 8-cm plastic pots filled with sandy soil. After two weeks, in both seasons, the seedlings (15 cm tall) were transplanted into plastic pots (30 cm diameter) filled with 6 kg of the same sandy soil. The physical and chemical characteristics of the soil are shown.
 
Soil analysis
 
The soil texture was sandy having the following characteristics: Coarse sand, 30.82%; fine sand, 62.61;  silt, 1.22%; clay, 5.35%; pH, 7.75; EC, 1.15 ds/m; organic matter, 0.08%; available N, 6.9 (ppm); available P, 6.2 (ppm); available K, 64 (ppm); CaCO3, 0.26%; and water holding capacity, 14.5%.
 
Treatments
 
At the beginning of the experimental, pots were supplied with recommended dose of NPK at a rate of 2.1 g/pot ammonium sulphate (20.5%) as nitrogen. Phosphorus was added as superphosphate (15.5%) at a rate of 1.2 g/pot and potassium was added as potassium sulphate at a rate of 0.3 g/pot. The seedlings were divided into seven treatments. The first one was un-inoculated control plants whereas the second treatment received only full dose of NPK after one month of each season. In the third treatment, the plants inoculated with mixed spores of AMF from genera (Glomus, Gigasporaand Acaulospora) (500 spores/g) at a rate of 3 g/hole, where spores dressed in a hole around the rhizosphere were attached to secondary roots (Massoud et al., 2009). Once the mycorrhizal symbiosis was established, A. chroococcumas a fourth treatment was prepared by growing on modified Ashby's medium 108 CFU/ml for 5 days (Abdel Malak and Ishac, 1968); whereas yeast strains as fifth and sixth treatments (S. cerevisiae and R. mucilaginosa) were also incubated at 28°C on rotary shaker at 150 rpm for 48 h in conical flasks (250 ml) containing 100 ml of glucose peptone yeast (GPY) medium (Difco, 1985). Then both were individually applied monthly at a rate of 5 ml/ pot. In addition, the mixture of previous inoculums (AMF, A. chroococcum, yeast strains) as seventh treatment was inoculated; it was isolated from very dry soil located at Tushka Valley Region, where there are great variations between the temperatures at day and night in winter and summer.
 
Irrigation intervals
 
The plants were irrigated every 3, 6, or 12 days. At each irrigation, the plants were watered till 100% of field capacity (F.C.). The soil moisture tension was measured before each irrigation using micro tension meters, and the quantity of water needed to reach 100% F.C. was calculated, as described by Richards (1949).
 
Experimental design
 
This experiment was factorial, conducted using a randomized complete blocks design with three replicates. The study included 21 treatments [7 treatments×3irrigation intervals], with each block consisting of 105 plants (5 plants/treatment).The treatments were applied regularly until the termination of each season (1st September in both seasons).
 
Growth parameters
 
Plant height, root length, number of branches/plant, as well as total fresh and dry weights /plant were recorded.
 
Microbial populations and AM fungi colonization
 
The population dynamics of total bacterial and yeast count in the rhizospheric zone of D. regia roots was determined by the plate count    technique   according   to   Reinhold   et   al.  (1985).  While Azotobacter spp. population counts in the rhizospheric zone of D. regia roots were determined using the most probable number (CFU/g rhizosphere) method described by Cochran (1950).
 
The percentage of AM fungi colonization in plant root tissues was also determined as described by Phillips and Hayman (1970).
 
Enzymatic activities determinations
 
Nitrogenase activity (N2-ase) in rhizosphere (roots) was measured as described by Somasegaran and Hoben (1994). The dehydrogenase activity was also estimated according to Skujins and Burns (1976).
 
Photosynthetic pigments, total carbohydrates and proline determinations
 
In addition, chemical analysis of fresh leaves samples was conducted to determine total chlorophyll (a+b) and carotenoids contents, using the method described by Nornai (1982). The content of total carbohydrates in dried leaves samples was determined using the method described by Dubois et al. (1956). The proline content in fresh leaves was also determined according to Bates et.al. (1973).
 
Determination of elements
 
Dried leaves samples were digested to extract nutrients as described by Piper (1950), and the extract was analyzed to determine its contents of nitrogen (using the modified micro-Kjeldahl method as described by Pregl (1945), phosphorus according to Jackson (1967) and potassium estimated photometrically using a Jenway flame photometer, according to Chapman and Pratt (1961).
 
Activities of antioxidant enzymes
 
Preparation of the enzymes extraction of leaves tissues was carried out at 40°C at 3:1 buffer: fresh weight (v/v) in a pastel and mortar with 100 mM potassium phosphate buffer (at pH 7.5) containing 1 mM EDTA, 3 mM DL-dithiothreitol and 5% (w/v) insoluble polyvinyl pyrolidone. The homogenates were centrifuged at 10000 rpm for 30 min and then the supernatants were stored in separate aliquots at 8°C (Vitoria et al., 2001). Antioxidant enzymes were assayed as follows; Catalase (CAT) by measuring the decrease in absorbance due to disappearance of H2O2at 240 nm according to Chance and Maely (1955), Peroxidase (POD) by spectrophotometry according to Amako et al. (1994). Enzymes activities were expressed as units/min/mg protein.
 
All the obtained data were subjected to statistical analysis of variance, and the means were compared using the "Least Significant Difference (L.S.D.)" test at the 5% level, as described by Little and Hills (1978). 


 RESULTS AND DISCUSSION

Growth parameters
 
The obtained results revealed that, the prolonged irriga-tion intervals had an adverse effect on the growth of D. regia plants, regardless of the effect of inoculation treat-ments (Table 1). In  both  seasons,  prolonging  irrigation intervals (12 days) steadily resulted in significant reduction in the values recorded for all of the growth parameters (plant height, root length, number of branches/plant, as well as total fresh and dry weights /plant). However, prolonged irrigation intervals from 3 to 6 days caused only a slight (insignificant) reduction in the mean values recorded for some studied growth parameters, whereas longer irrigation intervals (12 days) resulted in significant reduction in the values recorded for all of the vegetative characteristics.
 
 
It can be concluded that the reduction in the growth may be attributed to the participation of water in the cell division, cell expansion and cell enlargement. In addition, water stress reduction causes a decrease in transport of cytokinin from root to shoot and/or increase in Abscisic acid in leaf; these changes in the balance of hormones cause change in the extensibility in cell wall and these affect generally growth enlargement (Siddique et al., 2000; Ouma, 2005; Luvaha, 2005). This result has also been confirmed by Oyun et al. (2010) on Acacia senegal, and Liu et al. (2011) on apple.
 
The growth parameters of D. regia under different treatments as shown in Table 1 undoubtedly revealed that seedlings inoculated with dual bio-fertilizers significantly showed higher values in growth parameters compared to un-inoculated (control) plants at the recommended dose of NPK under the same conditions, in both seasons. Total fresh weight/plant was increased by 60.01 and 59.24% in the first and second seasons, respectively, over control plants.
 
These results provide a plausible mechanism of how the dual bio-fertilizers led to increase in growth para-meters in the control. This rise of their beneficial effects on seedlings represented in tolerance to drought pro-duces some growth promoting substances (Gibberellins, IAA and Abscisic acid, etc.), and vitamins which have favorable effects on root development (Alexander, 1977; Dobbelaere et al., 2003). Hyphae produced by AM fungi, which are microscopic tubes, colonize plant roots and grow out into the soil further than root hairs. The hyphae help in retaining moisture around the root zone of plants, and also increase nutrients uptake to the plant (especially diffusion of limited nutrient like P). Moreover, yeast contents of micro and macronutrients stimulate the plant to build up dry. In addition, they reduce diseases caused by root pathogens matter (Morte et al., 2001; Ortas et al., 2002; Hesham and Mohamed, 2011). Supportive evidence for this view was reported by Ibrahim (2009) on Flame seedless and Superior grapevines and Ibrahim et al. (2010) on Balady guava trees.
 
Microbial populations, mycorrhizal colonization (%), and enzyme activities
 
Data presented in Figures 1 and 2 also revealed that prolonged irrigation intervals had an adverse effect on the mean number  of  microbial  populations  (total  microbial, Azotobacter spp. and yeasts count), mycorrhizal colonization (%), as well as enzyme activities (nitogenase and dehydrogenase activities), regardless of the effect of inoculation treatments. In both seasons, prolonged irrigation intervals steadily reduced the values recorded for these pa-rameters. This reduction can be attributed to the role of water in enhancing the microbial activities (Ouma, 2007). Preceding results are in harmony with those obtained by Soliman (2008) on Acacia nilotica, who reported that the nitrogenase and dehydrogenase   activities   were  decreased  with prolonged irrigation intervals.
 
In general, microbial population, mycorrhizal colo-nization (%) and enzyme activities in the rhizosphere of D. regia were significantly affected by dual bio-fertilizers, as compared to the control which had the highest microbial populations, mycorrhizal colonization (%), as well as enzyme activities (Figures 1 and 2). Many studies have shown that the power of dual bio-fertilizers is due to their production of secondary metabolites that are essential for the growth of almost all the microorganisms, Nitrogenase and other proteins involved in nitrogen fixation (Brill, 1980; Muthuselvan and Balagurunathan, 2013). In addition, AMF development could be enhanced by supplying yeast vitamin B12, as it stimulates it (Boby et al., 2008). Also, AM fungi stimulate the activity of beneficial soil microorganisms (Boby and Bagyaraj, 2003) and root exudation is modified both qualitatively and quantitatively by A. mycorrhizal symbiosis. This leads to increase in mycorrhizal infection (Garg and Manchanda, 2009). Supportive evidence for this view was reported by Harisudan et al. (2010).
 
 
 
Chemical composition
 
Total chlorophyll and carotenoids content
 
Data recorded in the two seasons (Table 2) revealed that prolonged irrigation intervals had an adverse effect on the total chlorophyll and carotenoids contents in the leaves of D. regia plants, regardless of the effect of inoculation treatments. In both seasons, the contents of total chlorophyll and carotenoids were reduced steadily as the irrigation intervals were prolonged daily to 6 or 12 days. Drought stress causes reduction of the CO2 concentration in leaf internally. This is a result of stomata closure, changes in chlorophyll content, chlorophyll components and damage of the photosynthetic apparatus. All these led to the reduction rates of leaf photosynthetically. Also, producing reactive oxygen species (ROS) such as O2- and H2O2 can lead to lipid peroxidation and consequently, chlorophyll destruction (Foyer et al., 1994; Iturbe Ormaetxe et al., 1998; Lawlor and Cornic 2002; Flexas et al., 2004). Similar reductions in the chlorophylls content were reported by Mafakheri et al (2010), on Cicer arietinum and Arjenaki et al (2012) on Triticum aestivum.
 
Data presented in Table 2 also revealed that in both seasons, the total chlorophyll and carotenoids contents were affected by dual bio-fertilizers, as compared to the control plants. Plants inoculated with the dual bio-fertilizers had the highest total chlorophyll and carotenoids contents, followed by plants inoculated with AMF, then un-inoculated plants, in both seasons. These augmentations in the total chlorophyll and carotenoids content were in the favor of control plants which recorded 69.78 and 66.88%, respectively.
 
Similar results have been reported by El-Khateeb et  al. (2011) who stated that chlorophyll and carotenoids content in Acacia saligna were improved by inoculation with A. mycorrhizal fungi under water stress; also, Mazhar et al. (2010) on Jatropha curcas. The promotion of the synthesis and accumulation of chlorophyll may be attributed to the dual inoculation of AM fungi with other beneficial microorganisms that enhance mineral nutrition such as N, which is an essential component in the struc-ture of porphyrines, which are found in many metabolic active compounds, including chlorophylls. And also, the role of cytokine yeast that delays the aging of leaves. It does this by reducing the degradation of chlorophyll, leading to increase in chlorophyll content. Thus, it helps in higher photosynthetic rate (Castelfranco and Beale, 1983; Feng et al., 2002; Boby et al., 2008).
 
Total carbohydrates percentage and proline content
 
The data in Table 2 also showed that, in both seasons, prolonged irrigation intervals steadily increased the total carbohydrates percentage and proline content. These in-crements were 38.10 and 41.18%, respectively over control plants.
 
This behavior may be attributed to a reduction of carbohydrates translocation from leaves to other plant parts under drought conditions and/or the lesser consumption of carbohydrates in the leaves (El-Khateeb et al., 1991). Also, Hoekstra et al. (2001) mentioned that a high carbohydrate concentration decreases water potential, contributes in preventing oxidative damage, and maintains the structure of proteins and membranes under moderate dehydration during drought period.
 
The increase in the proline content of plants irrigated at long intervals is in agreement with the findings of El-Quesni et al. (2012) who reported that the proline content in leaves, stems and roots of Matthiola incana sig-nificantly increased as a result of decreased soil moisture level. This confirms that proline can biochemically adapt to stress condition.
 
The mean total carbohydrates percentage and proline content in leaves of D. regia were affected by dual bio-fertilizers (Table 2). In both seasons, plants inoculated with dual bio-fertilizers had the highest total carbohy-drates percentage and proline content, followedby plants inoculated with AMF, S. cerevisiae, A. chroococcum and R. mucilaginosa, full NPK, and then un-inoculated plants. The favorable effect of biofertilization on the synthesis and accumulation of carbohydrates and proline  may be attributed to the increase in the chlorophylls content of inoculated plants, and to the role played by nitrogen in the structure of porphyrine molecules (as previously mentioned), which are found in the cytochrome enzymes essential in photo-synthesis. This increase in the contents of chlorophylls and cytochrome enzymes results in an increase in the rate of photosynthesis, and a promotion in  carbohydrate  synthesis  and  accumulation(Devlin, 1975). The obtained results are in agreement with the findings of Khalid (2006) on Ocimum americanum and O. basilicum who found that the total carbohydrates increased when the plants were inoculated with myvorrhizal fungi under water stress. N, P and K (%).
 
 
The results in Table 2 also showed that the N, P and K percentages decreased steadily with prolonged irrigation intervals.   Accordingly,   the  lowest  percentages  of  the three nutrients were found in plants irrigated every 12 days; whereas the highest percentages were found in plants irrigated after 3 days, regardless of the effect of inoculation treatments. These results are in agreement with the findings of Jaleel et al. (2008) who indicated that water stress reduces growth by affecting various physiological and biochemical processes, such as ions uptake, translocation, and nutrient metabolism.
 
The results presented in Table 2 revealed that, in both seasons, D. regia plants inoculated with the dual bio-fertilizers had the highest N, P and K percentages in their leaf tissues, compared to  un-inoculated  (control)  plants.
 
 
These augmentations with reference to main macro-elements N, P and K were 55.36, 44.33 and 60.09%, respectively, in control plants. These results are in agreement with the findings of Jayakumar and Tan (2006) who indicated that seedlings of Acacia mangium inoculated with different strains of Bradyrhizobium had higher P contents compared to un-inoculated seedlings. AM fungi interact with other soil microbes like free-living nitrogen fixers and phosphate solubilizes to improve their efficiency for the biochemical cycling of elements to the host plants. Also, PGPR strains convert unavailable minerals and organic compounds into forms available to plants. In addition, PGPR strains usually have been found to increase the root length and root biomass and better developed root system. This may increase the mineral uptake in plants. This process increases nutrient uptake and availability of nutrients in the rhizosphere, resulting in an increase in plant growth and yield, as reported by Siddiqui and Mahmood (1999),  Gupta  et  al. (2002) and Khalid et al. (2004).
 
Activities of antioxidant enzymes
 
Our findings showed that by increasing the irrigation intervals (12 days), the activities of catalase (CAT) and peroxidase (POD) enzymes are significantly increased (1.74 and 3.70 µM/min/g FW, respectively, in the first season;1.66 and 3.39 µM/min/g FW, respectively, in the second season) compared to the respective 3 days (1.25 and 2.75 µM/min/g FW, respectively, in the first season; 1.00 and 2.55 µM/min/g FW, respectively, in the second season) (Figure 3). Abiotic stress such as drought causes damage directly or indirectly to plants, through re-active oxygen species (ROS) formation, which increases by increase  in  the  severity   of   drought   conditions.   This leads to the increase of tolerance to oxidative stress (Farooq et al., 2009). The increase in the activity of CAT and POD enzymes is in agreement with those found in Helianthus annuus (Nazarlil et al., 2011) and Boehmeria nitea (Huang et al., 2013), subjected to different watering regimes.
 
In this study, dual bio-fertilizers led to a significant increase in the CAT and POD enzymes compared to un-inoculated (control) plants (Figure 3). Borde et al. (2012); Heidari and Golpayegani (2012) and Morteza et al. (2013)  concluded that bio-fertilization can prevent oxide-tive stress by increasing activities of antioxidant enzymes during periods with intense photosynthesis; elevated acti-vity could be correlated with increased stress tolerance. Therefore, application of dual bio-fertilizers can be an important tool in D. regia cultivation to overcome drought stress conditions and can protect plants from drought conditions. The same previously mentioned trend was observed by other authors (Ruiz-Lozano et al, 2001; Alguacil, 2003; Saravanakumar et al., 2011).
 
It can be recommended to inoculate soil with A. mycorrhizal fungi combined with Azotobacter spp. and yeasts for increasing the tolerance of young seedlings of D. regia as well as enhancing growth, nutrition status and activities of antioxidant enzymes under drought condition, besides their safety for either environment or human health.


 CONFLICT OF INTEREST

The authors have not declared any conflict of interest.



 REFERENCES

Abd El-Malak Y, Ishac YZ (1968). Evaluation methods used in counting Azotobacter. J. Appl. Bact. 331: 269-275.
 
Alexander M (1977). Introduction to soil microbiology. 2nd ed., JohnWiley & Sons, Inc. New York. pp. 333-349.
 
Alguacil MM, Hernandez JA, Caravaca F, Portillo B, Roldan A (2003). Antioxidant enzyme activities in shoots from three mycorrhizal shrub species afforested in a degraded semi-arid soil. Physiol. Plant. 118: 562–570.
Crossref
 
Amako A, Chen K, Asada K (1994). Separate assays specific for ascorbateperoxidase and for chloroplastic and cytosolic isoenzymes of ascorbate peroxidase in plants. Plant Cell Physiol. 35: 497-504.
 
Arjenaki FG, Jabbari R, Morshedi A (2012). Evaluation of Drought Stress on Relative Water Content, Chlorophyll Content and Mineral Elements of Wheat (Triticum aestivum L.) Varieties. Int. J. Agric. Crop Sci. 4(11):726-729.
 
Aroca R, Ruiz-Lozano JM (2009). Induction of plant tolerance to semi-arid environments by beneficial soil microorganisms – A Review. Sustainab. Agric. Rev. 2:121-135.
 
Auudy B, Ferreira F, Blasina L, Lafon F, Arredondo F, Dajas R, Tripathi PC (2003). Screening of antioxidant activity of three Indian medicinal plants, traditionally used for the management of neurodegenerative diseases. J. Ethnopharmacol. 84: 131-138.
Crossref
 
Bates LS, Waldern RP, Teare LD (1973). Rapid determination of free proline under water stress studies. Plant Soil 39: 205-207.
Crossref
 
Boby VU, Bagyaraj DJ (2003). Biological control of root rot of Coleus forskohlii using microbial inoculants. World J. Microbiol. Biotechnol. 19:175–180.
Crossref
 
Boby VU, Balakrishna AN, Bagyaraj DJ (2008). Interaction between Glomusmosseae and soil yeasts on growth and nutrition of cowpea. Microbiol. Res. 163:693-700.
Crossref
 
Borde M, Dudhane M, Jite P (2012). Growth, water use efficiency and antioxidant defense responses of mycorrhizal and non mycorrhizal Allium sativum L. under drought stress condition. Ann. Plant Sci. 1(1):6-11.
 
Brill WJ (1980). Biochemical genetics of nitrogen fixation. Microbiol. Rev. 44:449-467.
 
Castelfranco PA, Beale SI (1983). Chlorophyll biosynthesis recent advances and areas of current interest. Ann. Rev. Plant Physiol. 34:241-278.
Crossref
 
Chance B, Maely AC (1955). Assay of catalase and peroxidase methods. Enzymology 2:755-784.
 
Chapman HD, Pratt PF (1961). Methods of Soil, Plants and Water Analysis. University of California Division of Agricultural Sciences. pp. 60-69.
 
Cochran WG (1950). Estimation of bacterial densities by means of the most probable number. Biometrics 6:105-116.
Crossref
 
Colla LM, Reinehr CO, Reichert C, Costa JAV (2007). Production of biomass and nutracenutical compounds by Spirulina platensis under different temperature, nitrogen sources. Bioresour. Technol. 98:1489-1493.
Crossref
 
Devlin RM (1975). Plant Physiology. Affiliated East-West Press Pvt., Ltd., New Delhi, 3rd Ed. pp. 221-240, 284-298 & 353.
 
Difco M (1985). Dehydrated culture media and reagents for microbiology. Laboratories Incorporated Detroit, Michigan, 48232 USA. P 621.
 
Du Puy DJ, Labat JN, Rabevohitra R, Villiers JF, Bosser J, Moat J (2002). The Leguminosae of Madagascar, Royal Botanic Gardens, Kew. 737p
 
Dubois M, Smith F, Gilles KA, Hamilton JK, Rebers PA (1956). Colorimetric method for determination of sugars and related substances. Ann. Chem. 28(3):350-356.
Crossref
 
Dobbelaere S, Vanderleyden J, Okon Y (2003). Plant growth promoting effects of diazotrophs in the rhizosphere. Crit. Rev. Plant Sci., 22:107–149.
Crossref
 
El-Khateeb MA, El-Naggar SM, Farahat MM (1991).Drought and salinity tolerance of Schinusmolle. Egypt. J. Appl. Sci. 6(5):1-22.
 
El-Khateeb MA, El-Leithy AS, Aljemaa BA (2011). Effect of mycorrhizal fungi inoculation and humic acid on vegetative growth and chemical composition of Acacia saligna Labill. seedlings under different irrigation intervals. J. Hortic. Sci. Ornam. Plants 3(3):283-289.
 
El-Quesni FEM, Mazhar AAM, Abd El Aziz NG, Metwally SA (2012). Effect of compost on growth and chemical composition of Matthiola incana (L.) R.Br. under different water intervals. J. Appl. Sci. Res. 8(3):1510-1516.
 
Farooq M, Wahid A, Kobayashi N, Fujita D, Basra SMA (2009). Plant drought stress: effects, mechanisms and management. Agron. Sustainb. Dev., 29:185–212.
Crossref
 
Feng G, Zhang FS, Li XL, Tian CY, Tang C, Rengel Z, (2002). Improved tolerance of maize plants to salt stress by Arbuscular mycorrhizal is related to higher accumulation of soluble sugars in roots. Mycorrhiza 12:185-190.
Crossref
 
Flexas J, Bota J, Loreto F, Cornic G, Sharkey TD (2004). Diffusive and metabolic limitations to photosynthesis under drought and salinity in C3 plants. Plant Biol. 6:1–11.
Crossref
 
Foyer CH, Descourvieres P, Kunert KJ (1994). Photo oxidative stress in plants. Plant. Physiol. 92:696-717.
 
Garg N, Manchanda G (2009). Role of arbuscular mycorrhizae in the alleviation of ionic, osmotic and oxidative stresses induced by salinity in Cajanus cajan (L.) Millsp. (pigeonpea). J. Agron. Crop Sci. 195:110-123.
Crossref
 
Gupta ML, Prasad A, Muni R, Sushil K (2002). Effect of the vesicular– arbuscular mycorrhizal (VAM) fungus Glomus fasciculatum on the essential oil yield related characters and nutrient acquisition in the crops of different cultivars of menthol mint (Mentha arvensis) under field conditions. Bioresour. Technol. 81(1):77-79.
Crossref
 
Harisudan C, Senthivel S, Arulmozhiselvan K (2010). Response of intercropping system, nutrient management and tree leaf extract sprays on cotton rhizosphere microbial population and seed cotton yield. Agric. J. 97(4-6):130-133.
 
Heidari M, Golpayegani A (2012). Effects of water stress and inoculation with plant growth promoting rhizobacteria (PGPR) on antioxidant status and photosynthetic pigments in basil (Ocimum basilicum L.). J. Saudi Soc. Agric. Sci. 11(1):57-61.
 
Hesham AL, Mohamed H (2011). Molecular genetic identification of yeast strains isolated from Egyptian soils for solubilization of inorganic phosphates and growth promotion of corn plants. J. Microbiol. Biotechnol. 21:55-61.
Crossref
 
Hoekstra FA, Golovina EA, Buitink J (2001). Mechanism of plant desiccation tolerance. Trends Plant Sci. 9:431-438.
Crossref
 
Huang C, Zhao, S, Wang L, Anjum SA, Chen M, Zhou H, Zou C (2013). Alteration in chlorophyll fluorescence, lipid peroxidation and antioxidant enzymes activities in hybrid ramie (Boehmeria nivea L.) under drought stress. A.J.C.S. 7(5):594-599.
 
Ibrahim HIM (2009). Response of Flame seedless and Superior grapevines grown on sandy calcareous soil to some phosphate dissolving bacteria treatments. J. Agric. Res. 87(1):285-299.
 
Ibrahim HIM, Zaglol MMA, Hammad AMM (2010). Response of balady guava trees cultivated in sandy calcareous soil to biofertilization with phosphate dissolving bacteria and /or VAM fungi. J. Amer. Sci. 6(9):399-404.
 
Iturbe Ormaetxe I, Escuredo PR, Arrese-Igor C, Becana M (1998). Oxidative damage in pea plants exposed to water deficit or paraquat. Plant Physiol. 116:173–181.
Crossref
 
Jackson ML (1967). Soil Chemical Analysis. Prentice-Hall, India. pp. 144-197.
 
Jaleel CA, Sankar B, Murali PV, Gomathinayagam M, Lakshmanan GMA, Panneerselvam R (2008). Water deficit stress effects on reactive oxygen metabolism in Catharanthus roseus: impacts on ajmalicine accumulation. Colloids Surf. B. Biointerfaces 62: 105-111.
Crossref
 
Jayakumar P, Tan TK (2006). Variations in the responses of Acacia mangium to inoculation with different strains of Brady rhizobium sp. under nursery conditions. Symbiosis Rehovot 41(1):31-37.
 
Khalid KHA (2006). Influence of water stress on growth, essential oil and chemical composition of herbs (Ocimum sp.). Int. Agrophysics 20: 289-296.
 
Khalid A, Arshad M, Zahir ZA (2004). Screening plant growth-promoting rhizobacteria for improving growth and yield of wheat. J. Appl. 96:473-480.
 
Lawlor DW, Cornic G (2002). Photosynthetic carbon assimilation and associated metabolism in relation to water deficits in higher plants. Plant Cell Environ. 25:275-294.
Crossref
 
Little TM, Hills FJ (1978). Agricultural Experimentation Design and Analysis, John Wiley & Sons, Inc., New York, USA. pp. 53-63.
 
Little ELJ, Wadsworth FH (1964). Common trees of Puerto Rico and the Virgin Islands. Agric. Handbook. Washington, DC: USDA Forest Service. pp. 176-177.
 
Liu B, Cheng L, Ma F, Zou Y, Liang D (2011). Growth, biomass allocation and water use efficiency of 31 apple cultivars grown under two water regimes. Agroforestry Syst. 1:1-13.
 
Luvaha E (2005). Effects of water stress on the growth of mango (Mangifera indica) rootstock seedlings. Msc. Thesis, Maseno University, Kenya. P 33.
 
Mafakheri A, Siosemardeh A, Bahramnejad B, Struik PC, Sohrabi E (2010). Effect of drought stress on yield, proline and chlorophyll contents in three chickpea cultivars. Aust. J. Crop Sci. 4(8):580-585.
 
Massoud ON, Ebtsam MM, El-Batanony NH (2009). Field response of snap bean (Phaseolus vulgaris L.) to N2-fixers Bacillus circulans and Arbuscular Mycorrhizal Fungi Inoculation through accelerating rock phosphate and feldspar weathering. Aust. J. Basic Appl. Sci. 3(2):844-852.
 
Mazhar AAM, Abd El Aziz NG, El Habba E (2010). Impact of different soil media on growth and chemical constituents of Jatropha curcas L. seedlings grown under water regime. J. Amer. Sci. 6:549-556.
 
Menninger EA (1962). Flowering trees of the world. New York: Hearthside Press. P 336.
 
Millat E, Mustafa M (1989). Effect of hot water treatment on the germination of seed of Albizzia lebbeck and D. regia. Bano Biggyan Patrika 8(1/2):63-64.
 
Morte A, Diaz G, Rodriguez P, Alarcon JJ, Sanchez-Blanco MJ (2001). Growth and water relation in mycorrhizal and nonmycorrhizal Pinus halepensis plants in response to drought. Biol. Plant. 44(2):263-267.
Crossref
 
Morteza M, Ahmad T, Hassanali N, Mehran OA, Shamsali R (2013). The biological fertilizers effects on the quality yield of Lippia citriodora plant. Int. J. Agron. Plant Prod. 4(5):1006-1012.
 
Muthuselvan I, Balagurunathan R (2013). Siderophore production from Azotobacter sp. and its application as biocontrol agent. Int. J. Curr. Res. Rev. 5(11): 23-35.
 
Nazarli H, Zardashti MR, Darvishzadeh R, Mohammadi M (2011). Change in activity of antioxidative enzymes in young leaves of sunflower (Helianthus annuus L.) by application of super absorbent synthetic polymers under drought stress condition. AJCS 5(11):1334-1338.
 
Nornai R (1982). Formula for determination of chlorophyll pigments ex-tracted with N.N. dimethyl formamide. Plant Physiol. 69: 1371-1381.
 
Ortas I, Ortakci D, Kaya Z, Cinar A, Onelge N (2002). Mycorrhizal de-pendency of sour orange in relation to phosphorus and zinc nutrition. J. Plant Nutr. 25:1263–1279.
Crossref
 
Ouma G (2005). Root confinement and irrigation frequency affect growth of 'Rough Lemon' (C. sinensis) rootstock seedlings. Fruits 60:3.
Crossref
 
Ouma G (2007). Growth parameters, photosynthesis, stomatal conductance and chlorophyll content of Avocado (Persea americana) rootstock seedlings as affected by different container sizes and different levels of irrigations frequency. ARPN J. Agric. Biol. Sci. 2(6):23-33.
 
Oyun MB, Adeduntan SA, Suberu SA (2010). Influence of watering regime and mycorrhizae inoculations on the physiology and early growth of Acacia Senegal (L.) Wild. Afr. J. Plant Sci. 4:210-216.
 
Phillips JM, Hayman DS (1970). Improved procedures for clearing roots and staining parasitic and vecsicular-arbuscular mycorrhizal fungi for rapid assessment of infection. Trans. Br. Mycol. Soc. 55:158-161.
Crossref
 
Piper CS (1950). Soil and Plant Analysis. University of Adelaide. Interscience Published, Inc. New York. pp. 258-275.
 
Pregl P (1945). Quantitative Organic Microanalysis. Appl. Churchill Publishing Co., London, 4th Ed., pp: 78-82.
 
Reinhold B, Hurek T, Fendrik L (1985). Strain-specific chemotaxis of Azospirillum spp. J. Bacteriol. 162:190-195.
 
Richards LA (1949). Methods of measuring soil moisture tension. Soil Sci. 68:95-112.
Crossref
 
Ruiz-Lozano JM, Collados C, Barea JM, Azcon R (2001). Cloning of cDNAS encoding SODs from lettuce plant with show differential regulation by Arbuscular mycorrhizal symbiosis and by drought stress. J. Exp. Botany 52:2241-2242.
 
Saravanakumar MK, Raguchander T, Subbian P, Samiyappan R (2011). Plant growth promoting bacteria enhance water stress resistance in green gram plants. Acta Physiol. Plant. 33(1): 203-209.
Crossref
 
Siddiqui ZA, Mahmood I (1999). Role of bacteria in the management of plant parasitic nematodes. A Review. Bioresource Technol. 69:167-179.
Crossref
 
Siddique MRB, Hamid A, Islam MS (2000). Drought stress effects on water relations of wheat. Bot. Bull. Acad. Sin. 41: 35-39.
 
Skujins J, Burns RG (1976). Extracellular enzymes in soil. Crit. Rev. Microbiol. 4(4):383-421.
Crossref
 
Soliman Sh A (2008). Effect of Rhizobia isolated from some Acacias on growth of Acacia nilotica under some stress conditions in North Africa. PhD Thesis, Institute of African Research and Studies, Cairo University. pp. 46-117.
 
Somasegaran P, Hoben HJ (1994). "Hand book for rhizobia." Springer-Verlag. New York. U.S.A. pp. 79-158.
Crossref
 
Treuner-Lange A, Kuhn A, Dürre P (1997). The kdp system of Clostridium acetobutylicum: cloning, sequencing, and transcriptional regulation in response to potassium concentration. J. Bacteriol. 179:4501-4512.
 
Vitoria AP, Lea PJ, Azevado RA (2001). Antioxidant enzymes responses to cadmium in radish tissues. Phytochemistry 57:701-710.
Crossref
 
Webb DB, Wood PJ, Smith JP, Henman GS (1984). A guide to species selection for tropical and sub-tropical plantations. Tropical Forestry Papers, 2nd ed. Oxford: University of Oxford, Commonwealth Forestry Institute. 256 p.
 
Wolters W, El Guindy S, El Deen MS, Roest K, Smit R, Froebrich J (2013). Assessment and management of water resources in Egypt to face drought and water scarcity. EGU Gen. Assem. Conf. Abstr. 15:10647.

 




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