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Seed Priming Effect on Symbiotic Germination and Seedling

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Seed Priming Effect on Symbiotic Germination and Seedling HORTSCIENCE 39(7):1700–1701. 2004. 5.25% NaOCl, and deionized (DI) water, fol- lowed by three 1-min rinses in sterile DI water. Then seeds were sown immediately according Seed Priming Effect on Symbiotic to the procedure described by Debeljak et al. (2002); 100 to 250 disinfested seeds for per Germination and Seedling petri dish were spread on the surface of 20 mL of oatmeal agar (2.5 g·L–1 rolled oats and 7.0 Development of Orchis palustris Jacq. g·L–1 agar in 1 L DI water at pH 6.0 before autoclaving at 121 °C for 15 min) contained Ahmet Esitken1 and Sezai Ercisli within 90-mm-diameter petri dishes. Each Department of Horticulture, Ataturk University, Faculty of Agriculture, 25240 treatment was replicated fi ve times. Each dish 3 Erzurum, Turkey was then inoculated with about 1 cm block of agar containing mycelium of the BNR 8-3 Cafer Eken isolate. The petri dishes were sealed with Department of Plant Protection, Ataturk University, Faculty of Agriculture, Parafi lm and incubated in white light (warm white fl uorescent) of 30 µmol·m–2·s–1 of 16 h 25240 Erzurum, Turkey photoperiod at constant 22 ± 1°C for 90 d. David Tay Seed germination was monitored daily for fi rst germination time. Seedling development were Ornamental Plant Germplasm Center, The Ohio State University, 670 Vernon scored for a duration of 90 d on a scale of 0 to Tharp Street, Columbus, OH 43210 5, where 0 = no germination; 1 = production of rhizoid (i.e., germination); 2 = rupture of Additional index words. orchid, Orchidaceae, osmoconditioning testa of the enlarged embryo; 3 = appearance Abstract. Seeds of Orchis palustris Jacq. were primed for 1- to 5-day in polyethylene glycol of promeristem; 4 = appearance of the fi rst true (PEG-6000) solutions at –0.5, –1.0 or –1.5 MPa. The seeds were symbiotically germinated leaf; and 5 = elongation of the fi rst true leaf and with BNR 8-3 mycorrhizal fungus on oatmeal agar at 22 °C. In general, priming hastened the formation of branched roots (Stewart and rapid germination. At –1.5 MPa water potential, the fi rst to germinate was eight days Zettler, 2002; Zettler and Hofer, 1998). compared to 18 days for the control. Percentage germination increased as priming water A germination (G) index was calculated to potential decreased, and the percentage germination was 55%, 58%, and 65%, at –0.5, take into consideration all the germinated seeds –1.0, and –1.5 MPa, respectively, versus 43% for the nonprimed control. Priming dura- in different stages of seeding development tion from 1 to 5 days had little effect on germination performance. The best germination (Scale 1 to 5) at the end of 90 d. The formula percentage (68%) was obtained from 1 day at –1.5 MPa treatment. used was as follows: G index = [germination % of stage 1 × 1 (scale Seeds of terrestrial orchid are dust-like, To date seed priming techniques have not been 1) + germination % of stage 2 × 2 (scale 2) + minute (0.07 to 0.40 mm width and 0.11 applied to symbiotic germination of orchids. ........ + germination % of stage 5 × 5 (scale to 1.97 mm length) and diffi cult to handle In the present study, we determined the effect 5)]/100. and germinate (Rasmussen, 1995). Orchid of priming with different concentrations of Statistical analysis. The experimental de- seeds do not have endosperm, and terrestrial PEG-6000 for varying periods on symbiotic sign used was a completely randomized with orchid seeds require mycorrhizal fungi as an seed germination and seedling development fi ve replications. Germination percentage, energy source (mycotrophy) in a symbiotic of Orchis palustris Jacq. germination index, fi rst germination time and relationship (Rasmussen, 1995) to initiate seedling development data were analyzed using seed germination and seedling development Materials and Methods analysis of variance (ANOVA), and mean com- (Arditti et al., 1984). Unfortunately, only a few parisons were made using Duncan’s multiple seeds out of millions produce this symbiotic Seed and fungal collection. Mature, nonde- range test and orthogonal contrast. relationship in nature (Arditti et al., 1984). In hisced yellowing capsules of Orchis palustris addition, in vitro symbiotic seed germination from the Erzurum district in Turkey were col- Results and Discussion and seedling development is lower than those lected in June 2002. After collection, seeds were of many other angiosperm seeds (Markovina dried in air at room temperature and 50% to All primed seeds had greater germination and McGee, 2000; Stewart and Zettler, 2002; 55% relative humidity (RH) for 2 d and stored and seedling development than nonprimed Zettler and Hofer, 1998). in sealed, sterile glass vials at 2 °C in total (control) seeds (Table 1). Germination percent- Seed priming, a process in which seeds darkness for 9 months. BNR 8-3 mycorrhizal ages were increased to an average of 65% for are imbibed to a desired moisture content to isolate, recovered from the root-like organs all –1.5 MPa water potential treatments, 58% arrest radicle emergence, followed by dry- of native Dactylorhiza urvilleana in Artvin, for all –1.0 MPa treatments, and 55% at all ing (McDonald, 2000), has resulted in more Turkey, was used because of its effectiveness –0.5 MPa treatments compared to 43% in the rapid and uniform germination in numerous in inducing seed germination and seedling control. Reducing the water potential to –1.5 plant species (Capron et al., 2000; Chen and development of Orchis palustris. MPa increased the germination index from 1.1 Sung, 2001; Pill and Kilian, 2000). A range Priming treatments. Seeds were imbibed in the control to 2.1. At –0.5 and –1.0 MPa, of osmotic substances has been used for in polyethylene glycol (PEG-6000) solutions the germination index averages were 1.6 and priming seeds, including mannitol, glycerol, at three water potentials (–0.5, –1.0, and –1.5 1.7, respectively. All priming treatments also sucrose and inorganic salts of K, Na and Mg MPa) according to Michel and Kaufmann induced faster germination (fi rst to germinate) (Heydecker and Coolbear, 1977; Parera and (1973), for 1, 2, 3, 4, or 5 d. The volume of as compared to the nonprimed seeds (control), Cantliffe, 1994), but most studies have been PEG solutions used for imbibition was 3 mL which took 18 d to germinate (Table 1). Seed conducted with polyethylene glycol (PEG), in 50-mm-diameter petri dish. Seeds were kept priming with PEG-6000 at –1.5 MPa increased a high-molecular-weight organic compound in darkness during priming at 25 ± 1°C. The the germination rate 22% compared to the (Capron et al., 2000; Pill and Kilian, 2000). imbibition solutions were not refreshed during control. incubation. Seeds were dried at 25 ± 1°C after The water potential of PEG treatments had Received for publication 15 Oct. 2003. Accepted imbibition for 1 d. signifi cant effects on seedling development for publication 1 May 2004. This study was sup- Seed sowing, fungal inoculation and (P < 0.001, Table 1). There was no difference ported by The Prime Ministry, The State Planning Organization, Republic of Turkey. germination assessment. Following priming, between the control and the –0.5 MPa treatments 1Corresponding author, e-mail aesitken@atauni. seeds were surface-sterilized for 1 min in a in seedling development (with score 5) but in edu.tr. 1:1:1 (by volume) mixture of absolute EtOH, the –1.0 MPa treatments there was an increase 1700 HORTSCIENCE VOL. 39(7) DECEMBER 2004 77812-Seed.indd812-Seed.indd 11700700 110/14/040/14/04 111:18:071:18:07 AAMM SEED TECHNOLOGY Table 1. Effects of seed priming on germination and seedling development of Orchis palustris Priming Seedling development (%) Germination Ψ (MPa) FGTz Stagey (stages 1–5) Germination duration (d) (d) 0 1 2 3 4 5x (%) index –0.5 1 15 46 0 25 12 12 6 55 1.6 –0.5 2 16 44 1 25 13 12 5 56 1.6 –0.5 3 13 44 0 27 14 9 6 56 1.6 –0.5 4 14 45 0 29 12 8 5 55 1.5 –0.5 5 17 44 0 28 14 9 5 56 1.6 Mean 15 aw 5.6 c 55.4 b 1.59 c –1.0 1 12 42 0 20 16 16 6 58 1.8 –1.0 2 11 41 1 29 13 11 6 59 1.7 –1.0 3 8 44 0 22 14 12 8 56 1.8 –1.0 4 10 42 0 22 15 12 8 58 1.8 –1.0 5 9 43 1 27 15 10 6 57 1.7 Mean 10 b 6.8 b 57.7 b 1.75 b –1.5 1 7 32 0 16 19 17 17 68 2.4 –1.5 2 7 35 1 17 16 19 13 65 2.2 –1.5 3 8 33 0 16 20 21 10 67 2.3 –1.5 4 8 35 0 24 19 15 7 65 2.0 –1.5 5 10 39 0 24 16 13 8 61 1.9 Mean 8 c 10.9 a 65.4 a 2.15 a Control 18 57 1 16 7 9 5 43 1.1 LSD 0.01 1.73 0.43 2.43 0.05 Ψ (MPa) Linear *** *** *** *** Quadratic * * *** *** Priming duration (d) Linear NS ** NS * Quadratic NS NS NS NS Qubic NS NS NS NS Quartic NS NS NS NS zFGT = fi rst germination time. yScale 0 to 5, where 0 = no germination, 1 = production of rhizoid (i.e., germination), 2 = rupture of testa of enlarged embriyo, 3 = appearance of promeristem, 4 = appearance of fi rst true leaf, 5 = elongation of the fi rst true leaf and formation of branched root.
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