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Abstract

‘Forest Green’ parsley ( Petroselinum crispum L.) seeds were leached for 3 days in aerated water at 25°C and then primed in aerated polyethylene glycol (PEG) 8000 solutions for 4.5 days at 25°. Priming improved earliness of germination at all temperatures of the tests (5°, 15°, 20°, and 25°), with the largest improvement at the coolest temperature. Uniformity of germination, as measured by the mean time between 25% and 75% germination, was not significantly affected by priming. Primed seeds germinated significantly faster than unprimed seeds when water stress was applied by low osmotic potentials (PEG solutions, -0.25, -0.5, or -0.75 MPa, were substituted for water). The latter result supports the hypothesis that priming induces the development of low cellular osmotic potentials. The priming effect was not lost during 8 months of storage, indicating a good treatment longevity.

Abstract

Priming seed of ‘Jalapeno M’ jalapeno pepper (Capsicum annuum L.) and ‘McIlhenny Select’ tabasco pepper (Capsicum frutescens L.) in 3% KNO₃ for 144 hours and –4 bar polyethylene glycol-6000 (PEG) for 120 hours enhanced germination rates, tested at 5° to 35°C. Seed priming stimulated jalapeno germination at 5°, but had no effect on tabasco when temperatures were less than 15°. Surface drying seed following priming retarded germination rate of both peppers over all temperatures as compared to primed seed not surface dried. Primed pepper seed performance in media under suboptimal temperatures (10° and 15°) was significantly less than that observed on filter paper. In the greenhouse, KNO₃-primed jalapeno seed had significantly earlier germination and accelerated vegetative seedling development. Priming in PEG appeared to retard jalapeno vegetative seedling development.

Abstract

Parsley (Petroselinum crispum L.) seeds osmoconditioned in −1.2 MPa polyethylene glycol 6000 (PEG) for 3 weeks at 15°C emerged earlier and gave higher seedling shoot fresh weights 24 days after planting than raw seeds. Further improvement in earliness of emergence was achieved by fluid-drilling the nongerminated, imbibed seeds in hydroxy ethyl cellulose gel. Germinating the osmoconditioned seeds (42% germination after 4 days at 15° in aerated water) before fluid-drilling decreased the time to 50% emergence by 52% and increased shoot fresh weight by 192% relative to raw seed performance. As emergence rate increased due to treatment, shoot fresh weight increased but emergence synchrony decreased. Neither grading seeds into density classes nor daily PEG replacement during osmoconditioning influenced seedling performance to a practical extent.

Abstract

The addition of (2RS, 3RS)-1-(4-chlorophenyl)-4,4-dimethyl-2-1,2,4-triazoI-1-yl-) pentan-3-ol) (paclobutrazol, PP333) at 0.05 or 0.20 ppm to a nutrient solution in which 4-month-old apple (Malus domestica, Borkh.) seedlings were growing, reduced terminal growth and increased root to leaf ratio. Plants pretreated with 0.20 ppm PP333 did not show a reduction in transpiration due to subsequent applied water stress induced by polyethylene glycol (PEG), whereas untreated plants decreased their transpiration in response to PEG stress at −0.5 and −0.75 MPa. The PP333 pretreatment at 0.20 ppm improved water balance of the seedlings since they had a higher water potential than untreated seedlings at equal or higher transpiration rates. Leaf osmotic adjustment to lower water potentials was shown to be leaf age-dependent irrespective of PP333 pretreatment.

Abstract

Shoot tip explants from tissue culture plantlets of five Rubus accessions (Rubus leucodermis Torr. & Gray, R. spectabilis Pursh, R. idaeus L. ‘Heritage’, Rubus spp. ‘Logan Thornless’ and ‘Merton Thornless’) were frozen slowly (0.8°C/min) to -40° and then rapidly to -196° in the presence of cryoprotectants. Following rapid thawing, regrowth as organized apical growth or as callus occurred on agar media. A combination of polyethylene glycol (PEG), glucose, and dimethylsulfoxide (PGD) was the most successful cryoprotectant.

NaCl, KNO₃ (0.3, 0.4, 0.5M), KH₂P O₄ (0.4, 0.5, 0.6M), and PEG 8000 (320 to 370 g/L with the increment of 10g/L) were used for priming Petunia `Ultra White' seeds for three to six days. Seeds were germinated in a growth chamber at 25C. Germination was recorded for seven days and the number of acceptable seedlings (seedlings with open cotyledon and normal root) was counted on the day seven. KH₂P O₄ at 0.6M was the best salt treatment. Rate of germination was improved by salt priming but the number of acceptable seedlings was lower than the control. Addition of GA (5 ppm) to the salt treatment was not effective. More abnormal seedlings were observed when seeds were primed in aerated salt solutions than when primed in petri dishes. Aerated PEG at 325 g/L for three days and 365 g/L for six days gave the best results. Priming in PEG improved percent of germination, rate of germination, and number of acceptable seedling as compared to control. Primed seeds lost some of the advantages of priming during 24hr air drying (22C), however quality was maintained when dried at 10C. Drying primed seed in 80% R.H. was not effective.

NaCl, KNO₃ (0.3, 0.4, 0.5M), KH₂P O₄ (0.4, 0.5, 0.6M), and PEG 8000 (320 to 370 g/L with the increment of 10g/L) were used for priming Petunia `Ultra White' seeds for three to six days. Seeds were germinated in a growth chamber at 25C. Germination was recorded for seven days and the number of acceptable seedlings (seedlings with open cotyledon and normal root) was counted on the day seven. KH₂P O₄ at 0.6M was the best salt treatment. Rate of germination was improved by salt priming but the number of acceptable seedlings was lower than the control. Addition of GA (5 ppm) to the salt treatment was not effective. More abnormal seedlings were observed when seeds were primed in aerated salt solutions than when primed in petri dishes. Aerated PEG at 325 g/L for three days and 365 g/L for six days gave the best results. Priming in PEG improved percent of germination, rate of germination, and number of acceptable seedling as compared to control. Primed seeds lost some of the advantages of priming during 24hr air drying (22C), however quality was maintained when dried at 10C. Drying primed seed in 80% R.H. was not effective.

Purple coneflower seeds following priming (-0.04 MPa, 10 days, 15C, darkness) osmotically in polyethylene glycol 8000 (PEG) or matrically in expanded no. 5 vermiculite had greater germination rate and synchrony at continuous 20C or 30C than untreated seeds, but germination percentage was unaffected. Inclusion of 5.5 × 10^-2 M gibberellic acid (GA₃ as ProGibb Plus 2X, Abbott Laboratories, N. Chicago, Ill.) further improved germination rate and synchrony at 20C, but not at 30C. In a greenhouse study (30C day/27C night, July-August natural light), seeds primed in PEG or vermiculite containing G A₃ compared to untreated seeds had 6 percentage points higher maximum emergence (ME), 3.3 fewer days to 50% ME, 1.9 fewer days between 10% and 90% ME, 116% greater shoot dry weight, and 125% longer leaves at 16 days after planting in peat-lite. Inclusion of ethephon (0.01 m, as Florel) either alone or with GA₃ during priming provided no benefit to seed germination or seedling emergence. Moistened vermiculite substituted for PEG solution as a priming medium for purple coneflower seeds, the priming benefit on seedling emergence and growth being enhanced by 5.5 × 10^-2 m G A₃ inclusion in the priming media.

Immature florets were inoculated on MS basal salt media (3% sucrose + 0.8% agar) + 1.0 mg 2,4-D/liter to induce embryogenic callus. Induced embryogenic callus was sieved through serial metal mesh screens (40 and 60 mesh) and placed on the embryo induction media at different concentrations of cytokinins and osmotica. BAP (0.1 mg^–liter^–1) or TDZ (0.001, 0.01, 0.1, and 1.0 mg^–liter^–1) were treated on 1/2 MS (3% sucrose) according to the following schedules: 1) first 2 weeks of treatments, followed by 3 weeks of 1/2 MS (3% sucrose) (FT); 2) first 3 weeks of 1/2 MS (3% sucrose), followed by 2 weeks of treatment (LT); and 3) 5 weeks of treatments. PEG, mannitol (0, 2.5%, 5.0%, 7.5%, and 10.0%), and sucrose (0%, 3%, 6%, 9%, and 15%) also were used as osmotica with ABA (0.05 mg^–liter^–1), respectively. The treatment schedules were FT and LT. Several good quality embryos were produced at 0.001 mg TDZ/liter, 0.1 mg BAP/liter, or 7.5% and 10.0% PEG (only FT). Abnormal embryos were significantly reduced at 7.5% and 10.0% PEG. Leaves of the plants obtained through somatic embryos were compared with those of seed-propagated plants before and after acclimatization using SEM. Epidermal and conductive tissues developed little in the plants before acclimatization; however, they developed gradually after acclimatization and were similar to those of seed-propagated plants.

Priming regimes were evaluated on pansy seeds (Viola ×wittrockiana Gam. `Crystal Bowl Sky Blue') in high-temperature germination tests. Priming regimes evaluated included CaCl₂, MgCl₂, K₂HPO₄, Na₂HPO₄, NaCl, KCl, KNO₃, Na₂SO₄, and polyethylene glycol 15,000 (PEG_15,000) at –1.0 and –2.0 MPa, for 3, 6, or 9 d at 23 °C. Primed and nonprimed control seeds were then germinated at 25, 30, or 35 °C. Total percent germination of nonprimed control seeds was significantly less at 35 °C than at 25 °C. Seeds primed with CaCl₂ at –1.0 MPa for 3 d at 23 °C had significantly higher germination at 35 °C than all other priming regimes tested, including aerated PEG₈₀₀₀ at –1.0 MPa for 7 d at 15 °C. Seed respiration, measured by O₂ uptake, during germination of seeds primed with CaCl₂ was higher than for control seeds or those primed with PEG₈₀₀₀. Priming pansy seed with CaCl₂ at –1.0 MPa for 3 d at 23 °C was effective in increasing seedling emergence and for reducing the time of emergence in summer greenhouse studies.