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Effects of priming on seed germination of Marigold (Calendula officinalis).

Introduction

Marigold (Calendula officinalis) as an important medicinal plant has been cultivated and adopted in most area in Iran. Seeds are most important factors in existence and proliferation of plants and their quality define plants productivity in agricultural ecosystems. Thus characterization of decreasing factors of seed quality and applying methods in order to optimizing these characteristics are managements that can improve productivity of crops. Germination and seedling establishment are critical stages in the plant life cycle. In crop production, stand establishment determines plant density, uniformity and management options [6]. In arid and semi-arid environments, the water needed for germination is available for only a short period, and consequently, successful crop establishment depends not only on the rapid and uniform germination of the seed, but also on the ability of the seed to germinate under low water availability [11]. However, if the stress effect can be alleviated at the germination stage, chances for attaining a good crop with economic yield production would be high [3].

Strategies for improving the growth and development of crop species have been investigated for many years. Seed priming is a pre-sowing strategy for influencing seedling development by modulating pre-germination metabolic activity prior to emergence of the radicle and generally enhances germination rate and plant performance [4,32]. During priming, seeds are partially hydrated so that pre-germination metabolic activities proceed, while radicle protrusion is prevented, then are dried back to the original moisture level [21].

Various prehydration or priming treatments have been employed to increase the speed and synchrony of seed germination [4]. Common priming techniques include osmopriming (soaking seeds in osmotic solutions such as polyethylene glycol), halopriming (soaking seeds in salt solutions) and hydropriming (soaking seeds in water). Osmopriming contributes to significant improvement in seed germination and seedling growth in different plant species. Seeds of tomato and asparagus (Asparagus offcinalis) osmoconditioned in -0.8 MPa PEG-8000 showed increased germination under saline media [25]. Osmotic priming to improve seed germination performance may also enhance general crop performance. osmoconditioning of Italian ryegrass (Lolium multiflorum) and sorghum (Sorghum bicolor) seeds with 20% PEG-8000 for 2 d at 10[degrees]C increased germination percentage, germination rate, seedling establishment and dry matter production under water stress, water logging, cold stress and saline conditions [15].

This simple, low-cost, low-risk intervention also had positive impacts on the wider farming system and livelihoods and the technology has proved highly popular with farmers [13,14]. Its value has already been shown for many crops, for example wheat [13,26]; chickpea [23,18], maize [3], mungbean [27], pigeon pea [17], sunflower [19] and Barley [1].

This research was conducted to investigate the effects of osmo-priming on seed germination of Marigold.

Materials and Methods

In this research, seed of Marigold (Calendula officinalis) which is commonly grown in Iran, was used. Seeds were pre-treated with a mixture of benomyl and thiram fungicides at a rate of 3.3 g/kg, in order to control possible fungal contamination during priming. Seed sample was divided into two sub-samples. One of the sub-samples was considered as control (unprimed) and the other sub-samples was prepared for priming treatments.

Seed priming

Seeds of were pretreated with Polyethylene glycol 6000 (PEG) at concentrations of -3, -6 and -12 bar [22] for 24 hours. Priming treatments were performed in an incubator adjusted on 20[+ or -]1[degrees]C under dark conditions. After priming, samples of seeds were removed and rinsed three times in distilled water and then dried to the original moisture level.

Laboratory germination:

Three replicates of 25 seeds were transferred to Petri dish. Seeds were allowed to germinate at 10[+ or -]1[degrees]C in the dark for 21 days. Germination was considered to have occurred when the radicles were 2mm long. Germinated seeds were recorded every 24 h for 21 days. Rate of seed germination (R) was calculated according to Ellis and Roberts, [10].

R = [summation]n/[summation]D.n

Where n is the number of seeds germinated on day D, D is the number of days counted from the beginning of the test and R is mean germination rate. At the end of germination test (21 days), roots and shoots were cut from the seedling and then dried in an oven at 75[+ or -]2[degrees]C for 24 hours. The dried radicle and shoots were weighted to the nearest milligram and the mean radicle and shoot dry weight and consequently mean seedling dry weight were determined.

Experimental design

Laboratory tests were carried out at the Seed Technology Laboratory of Shahed University, Iran, using randomized complete block (RCBD) design with 3 replicates. Analysis of variance (ANOVA) of the laboratory was carried out, using SAS software (SAS, 2001). Excel software was used to draw figures. Means were compared by applying Duncan test at 5% probability.

Results and Discussion

Analysis of variance showed that the effect of osmotic priming treatments on all measuring characters were significant (Table 1).

Mean comparisons of studding characters wholly showed that priming with osmotic potential of solution, increased amount of the characters. Result showed that priming seeds with solution of -6 (bar) produced the higher germination percentage, compared to ther seed treatments (Figure 1). Mean comparisons of priming treatment for germination rate showed that priming treatment in contrast to control, has the higher germination rate. The highest germination rate was obtained for seeds primed with peg (-6) bar (Figure 1). Probably high osmotic potential (-12 bar) does not let seed absorb required water for starting metabolic activities and probably production of oxygen free radical at this condition can also damage cell membrane thus advantage effect of priming disappears. Whereas suitable conditions of osmotic priming with PEG in wild rye resulted in higher Super Oxide Dismotase (SOD) and Proxidase activity ultimately resulted in higher germination rate [16].

Priming with peg -6 bar produced the largest root and shoot, compared to control (fig 1). About Pinus sylvestris and Larix deciduas seeds, it was reported that priming with PEG+ 200 mg [kg.sup.-1] gibberlic acid ([GA.sub.3]) resulted in appreciably higher free radical contents than in unprimed control sample [24]. Seed priming had significant effect on seedling weight and the highest seedling weight was obtained for seeds primed with peg (-12) bar. Seedling weight was statistically similar for primed with solution of -6 (bar) and unprimed seeds (Figure 1). Enzymes such as amylase, protease and lipase have a great role in initial growth and development of embryo. Every increase in activity of these enzymes results in faster initial growth of seedling therefore its establishment improvement result in higher yield. As Singh et al. [30] reported that osmotic priming of muskmelon with PEG result in higher amylase and dehydrogenase activity and germination rate in saline condition increased.

[FIGURE 1 OMITTED]

Several works have shown the improvement in seed performance after priming. This includes increasing seed germination rate [28], uniformity [5] and seedling growth [20]. This improvement is a consequence of physiological changes during the priming process which affects protein [31,12] enzyme [8,33], DNA [2] and RNA [7,9] synthesis and activity.

By results of this experiment, we can conclude that suitable priming can result in higher germination indices.

References

[1.] Abdulrahmani, B., K. Ghassemi-Golezani., M. Valizadeh, V. Feizi-Asl, 2007, Seed priming and seedling establishment of barley (Hordeum vulgare L.). J. Food. Agri. Environ., 5: 179-184.

[2.] Ashraf, M. and Bray, C.M. 1993. DNA synthesis in osmoprimed leek (Allium porrum L.) seeds and evidence for repair and replication. Seed Sci. Res., 3: 15-23.

[3.] Ashraf, M., H. Rauf, 2001, Inducing salt tolerance in maize (Zea mays L.) through seed priming with chloride salts, growth and ion transport at early growth stages. Acta Physiol. Plant., 23: 407-414.

[4.] Bradford, K.J., 1986. Manipulation of seed water relations via osmotic priming to improve germination under stress conditions. Hurt. Sci., 21: 1105-1112.

[5.] Bodsworth, S. and J.D. Bewley, 1981. Osmotic priming of seeds of crop species with polyethylene glycol as means of enhancing early synchronous germination at cool temperatures. Can. J. Bot., 59: 672-676.

[6.] Cheng, Z., K. J. Bradford, 1999, Hydrothermal time analysis of tomato seed germination responses to priming treatments,. Journal of Experimental Botany, 33: 89-99.

[7.] Coolbear, P., R.J. Slater and J.A. Bryant, 1990. Changes in nucleic acid levels associated with improved germination performance of tomato seeds after low-temperature presowing treatment. Ann. Bot., 65: 187-195.

[8.] Dell'Aquila, A. and P. Spada, 1992. Regulation of protein synthesis in germination wheat embryos under polyethylene glycol and salt stress. Seed Sci. Res., 2: 75-80.

[9.] Davison, P.A., R.M. Taylor and C.M. Bray, 1991. Changes in ribosomal RNA integrity in leek (Allium porrum L.) seeds during osmoconditioning and drying-back treatments. Seed Sci. Res., 1: 37-44.

[10.] Ellis, R.H., E.H. Roberts, 1980, Towards rational basis for testing seed quality, Hebblethwaite, P. D. (Ed.), Seed Production, Butterworths, London, 605-635.

[11.] Fischer, R.A., N.C. Turner, 1978, Plant productivity in the arid and semiarid zones. Ann. Rev. Plant Physiol., 29: 277-317.

[12.] Fujikura, Y. and C.M. Karssen, 1992. Effects of controlled deterioration and osmoconditioning on protein synthesis of cauliflower seeds during early germination. Seed Sci. Res., 2: 23-31.

[13.] Harris, D., B.S. Raghuwanshi., J.S. Gangwar, S. C. Singh, K.D. Joshi, A. Rashid, P.A. Hollington, 2001, Participatory evaluation by farmers of 'on-farm' seed priming in wheat in India. Nepal and Pakistan, Exp. Agric., 37: 403-415.

[14.] Harris, D., A. Joshi, P.A. Khan, P. Gothkar, P. S. Sodhi, 1999. On-farm seed priming in semiarid agriculture development and evaluation in maize, rice and chickpea in India using participatory methods. Exper Agric., 35: 15-29.

[15.] Hur, S.N., 1991. Effect of osmoconditioning on the productivity of Italian ryegrass and sorghum under suboptimal conditions. Korean J. Animal Sci., 33: 101-105.

[16.] Jie, L.L. Ong She, O. Dong Mei, L. Fang and W. Hua En, 2002. Effect of PEG on germination and active oxygen metabolism in wildrye (Leymus chinesis) seed. Acta prataculture Sinica., 11: 59-64.

[17.] Jyotsna, V., A.K. Srivastava, 1998. Physiological basis of salt stress resistance in pigeonpea (Cajanus cajan L.)-II, Pre-sowing seed soaking treatment in regulating early seedling metabolism during seed germination. Plant Physiol. Biochem., 25: 89-94.

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[19.] Kaya, M.D., G. Okcu., M. Atak., Y. Ikili, O. Kolsarici, 2006. Seed treatments to overcome salt and drought stress during germination in sunflower (Helianthus annuus L.). Europ. J. Agr., 24: 291-295.

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[22.] Michel, B.E., M.R. Kaufmann, 1973. The osmotic potential of polyethylene glycol 6000. Plant Physiol., 51: 914-916.

[23.] Musa, A.M., D. Harris., C. Johansen., J. Kumar, 2001. Short duration chickpea to replace fallow after aman rice: the role of on-farm seed priming in the High Barind Tract of Bangladesh,.Exp. Agric., 37: 509-521.

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[27.] Rashid, A., D. Harris., P.A. Hollington., M. Rafiq, 2004. Improving the yield of mungbean (Vigna radiata) in the North West Frontier Province of Pakistan using on-farm seed priming. Exp. Agric., 40: 233-244.

[28.] Ruan, S., Q. Xue and K. Tylkawska, 2002. The influence of priming on germination of rice seeds and seedling emergence and performance in flooded soil. Seed Sci. Technol., 30: 61-67.

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[31.] Smith, P.T. and B.G. Cobb, 1991. Physiological and enzymatic activity of pepper seeds (Capsicum annum) during priming. Physiologia Plantarum, 82: 433-439.

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[33.] Sung, F.J.M. and Y.H. Chang, 1993. Biochemical activities associated with priming of sweet corn seeds to improve vigor. Seed Sci. Technol., 21: 97-105.

Corresponding Author

Reza Jabbari, Department of Agronomy, Shahed University, P.O.Box: 18151/159

Tehran, Iran. E-mail: re_jabbari@yahoo.com

(1) Fatemeh Ganji Arjenaki, (2) Majid Amini Dehaghi, (1) Reza Jabbari

(1) Department of Agronomy, Shahed University, P.O. Box: 18151/159 Tehran, Iran.

(2) Assistant Professor of Agronomy Department of Agriculture Faculty and Research Center of Medicinal Plant, Shahed University

Fatemeh Ganji Arjenaki, Majid Amini Dehaghi, Reza Jabbari: Effects of Priming on Seed Germination of Marigold (Calendula officinalis)
Table 1: Analysis of variance for seed priming effects on marigold
seed germination

Source of      Degree of      Germination    Germination
variation      freedom        percentage     rate

Treatment      3              0.25 **        0.02 **
Error          8              0.0005         0.0005
CV (%)                        3.7            7.4

Source of      Radicle        Shoot          Seedling
variation      length         length         weight

Treatment      3 **           6.1 **         0.000004 **
Error          0.07           0.2            0.0000002
CV (%)         13             12             10.7

** significant at p% 0.01, CV = Coefficient of variation
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Title Annotation:Original Article
Author:Arjenaki, Fatemeh Ganji; Dehaghi, Majid Amini; Jabbari, Reza
Publication:Advances in Environmental Biology
Article Type:Report
Geographic Code:7IRAN
Date:Jan 1, 2011
Words:2282
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