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  • Author or Editor: Wallace Pill x
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Seed treatments, gels, and planters associated with fluid drilling are reviewed in detail. The future of fluid drilling likely lies predominantly in the sowing of primed seeds rather than germinated seeds in the carrier gel. The primed seeds may be hydrated before fluid drilling to enhance germination and seedling emergence. The gel can carry a variety of chemical or biological additives appropriate for the crop and seedbed conditions. The positional advantage resulting from additive incorporation in the fluid-drilling gel represents a more eflicient, cost-effective, and environmentally sound application method than others such as binding or spraying.

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Seeds of `Ace 55VF' tomato were soaked in solutions of -1.0 MPa Instant Ocean™ (inorganic salt mixture) or -0.6 MPa polyethylene glycol 8000 (P.E.G.) at 25 C for 1 week. `Mary Washington' asparagus seeds were soaked in the same solutions for 2 weeks. In solutions of decreasing matric or osmotic potentials, primed seeds germinated faster than untreated seeds. Germination percentages of primed seeds generally were greater than those of untreated seeds when water stress exceeded -0.5 MPa. All primed seeds, whether dried to a low moisture content or not, germinated faster than untreated seeds after storage for up to 3 months at 4 C or 20 C. Primed asparagus seeds germinated most rapidly and synchronously after storage at 4 C and high moisture content. Storage temperature and seed moisture content had no effect on subsequent germination of primed tomato seeds.

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Following dry storage for 5 or 11 months (new and old seeds, respectively) at 5 °C, less than 10% of the seeds of Indiangrass germinated as determined by a standard germination test. We attempted to increase germination by subjecting seeds to dormancy-breaking treatments, including sodium hypochlorite soak (5.25% v/v NaOCl; 20 or 60 min), prechilling (5 °C for 2 weeks), gibberellic acid during germination (GA3, 1000 mg·L-1), and combinations thereof. Treatment with NaOCl increased the germination of non-prechilled seeds only when they were germinated in GA3; a 60-min soak in NaOCl increased germination to 53% and 65% in new and old seeds, respectively. Prechilling increased germination to 65% and 47% in new and old seeds, respectively. Germination of new, prechilled seeds was increased further to 86% by either a 20-min soak in NaOCl or germination in GA3. Germination of old, prechilled seeds was not promoted further by treatment with NaOCl, but was increased to 67% by germination in GA3. Since NaOCl treatment alone failed to promote germination, we examined the effects on seedling emergence and growth of providing GA3 at 1000 mg·L-1 during the 2-week prechilling period. While prechilling alone increased emergence to an average 34% for new and old seeds, prechilling with GA3 increased emergence to 75% and 50% for new and old seeds, respectively. These treatments did not influence seedling shoot dry mass. Seed exposure to GA3 during rather than after prechilling was more effective in promoting Indiangrass establishment.

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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.

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We examined the efficacy of coir dust (CD)—the short fibers and dust from the mesocarp of coconuts (Cocos nucifera L.)—as an alternative to sphagnum peat (SP) in 50 SP : 50 vermiculite (% volume) medium. Shoot dry mass of coreopsis (Coreopsis lanceolata L.) or `Red Robin' tomato (Lycopersicon esculentum Mill.) after 5 weeks' growth in up to 50 CD : 50 vermiculite (% volume) was similar to that in 50 SP : 50 vermiculite and a commercial peat-lite (Pro-Mix BX). These growth responses depended on preplant controlled-release fertilizer (CRF) [Osmocote 17N-3.9P-10.8K at 11.5 lb/yd3 (4 kg·m−3)] and/or a post-transplanting weekly solution fertilization (SF) at 350 ppm (mg·L−1) N from 21N-2.2P-16.6K. Compared to SP, CD had lower bulk density and cation exchange capacity (volume basis) and higher C to N ratio, pH, total porosity, and container capacity. We conclude that CD is an adequate alternative to SP in soilless container media.

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`Moss Curled' seeds of parsley (Petroselinum crispum L.) were primed osmotically in polyethylene glycol or matrically in fine, exfoliated vermiculite at -0.5 MPa for 4 or 7 days at 20 or 30 °C with 0 or 1 mm GA3. All priming treatments stimulated and hastened germination. Matric priming resulted in greater germination (89%) than osmotic priming (83%) when seeds were primed for 7 days at 30 °C, but priming agent had no effect on germination percentage following priming at 20 °C or for 4 days. In seeds primed for 4 days at 20 or 30 °C, matric priming hastened germination more than did osmotic priming. Germination was generally less synchronous with matric than with osmotic priming. Increasing priming time from 4 to 7 days increased the rate of germination, but increased germination synchrony only when seeds were primed a t 20 °C. Inclusion of 1 mm GA3 during priming had little or no effect on germination. All matric priming treatments (other than 4-day priming) were repeated to assess seedling emergence in a greenhouse (25°C day/22 °C night). Priming increased the percentage, rate and synchrony of emergence, and increased hypocotyl length at 3 weeks after planting. Priming at 30 °C with 1 mm GA3 resulted in the greatest emergence percentage, hypocotyl length, and shoot dry weight. We conclude that matric priming is a satisfactory alternative to osmotic priming of parsley seeds. Chemical name used: gibberellic acid (GA3).

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Seed treatments with paclobutrazol (PB), a triazole growth retardant, were examined for seedling growth suppression without exerting a deleterious effect on germination or emergence. Seeds of `Salmon Picotee impatiens (Impatiens wallerana Hook f.) and `Marglobe tomato (Lycopersicon esculentum Mill.) were soaked for 24 or 48 hours at 22 °C in 0, 50, 500, or 1000 mg·L-1 PB or were primed in polyethylene glycol 8000 or grade 5 exfoliated vermiculite (both at -1.0 MPa for 7 days at 22 °C) containing these PB solutions. Any PB seed treatment of impatiens (including a series of lower concentrations up to 50 mg·L-1 PB) that elicited seedling growth suppression also reduced germination and emergence. For tomato, soaking seeds for 24 hours in up to 1000 mg·L-1 PB had little or no effect on germination or emergence, and yet shoot height or dry weight was not decreased further by exceeding 50 mg·L-1 PB. At any PB concentration, soaking seeds for 48 hours or priming seeds resulted in lower percentage of germination or emergence than soaking seeds for 24 hours. Soaking tomato seeds in 50 mg·L-1 PB for 24 hours resulted in similar shoot growth suppression until at least 31 days after planting as a growth medium drench (1 mg·L-1 PB) or as a shoot spray (10 mg·L-1 PB), both applied at 14 days after planting. Beyond 31 days after planting, however, the latter two treatments gave greater shoot growth suppression than the PB seed soak treatment, which had lost its growth suppressive effect. Chemical name used: (+)-(R *,R *)-[(4-chlorophenyl)methyl]- -(1,1,-dimethyl)-1H-1,2,4-triazole-1-ethanol (paclobutrazol).

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`Moss Curled' seeds of parsley (Petroselinum crispum L.) were primed osmotically in polyethylene glycol or matrically in fine, exfoliated vermiculite at –0.5 MPa for 4 or 7 days at 20 or 30 °C with 0 or 1 mm GA3. All priming treatments stimulated and hastened germination. Matric priming resulted in greater germination (89%) than osmotic priming (83%) when seeds were primed for 7 days at 30 °C, but priming agent had no effect on germination percentage following priming at 20 °C or for 4 days. In seeds primed for 4 days at 20 or 30 °C, matric priming hastened germination more than did osmotic priming. Germination was generally less synchronous with matric than with osmotic priming. Increasing priming time from 4 to 7 days increased the rate of germination, but increased germination synchrony only when seeds were primed at 20 °C. Inclusion of 1 mm GA3 during priming had little or no effect on germination. All matric priming treatments (other than 4-day priming) were repeated to assess seedling emergence in a greenhouse (25°C day/22 °C night). Priming increased the percentage, rate and synchrony of emergence, and increased hypocotyl length at 3 weeks after planting. Priming at 30 °C with 1 mm GA3 resulted in the greatest emergence percentage, hypocotyl length, and shoot dry weight. We conclude that matric priming is a satisfactory alternative to osmotic priming of parsley seeds. Chemical name used: gibberellic acid (GA3).

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The influence of two drying regimes and two storage temperatures of primed asparagus (Asparagus officinalis L.) and tomato (Lycopersicon esculentum Mill.) seeds on germination after storage up to 3 months was examined. Seeds of `Mary Washington' asparagus and `Ace 55' tomato primed in synthetic seawater (-1.0 MPa, 20C, 1 week, dark) were surface-dried at 20C and 50% relative humidity (RH) for 2 h (42% to 49% moisture) or dried-back at 20C and 32.5% RH for 48 h (moisture = 13% tomato and 22% asparagus). These and nonprimed seeds were stored in tight-lidded metal cans and heat-sealed plastic pouches at 4 or 20C for up to 3 months before germination at 20C. After 3-month storage, primed surface-dried asparagus seeds stored at 4C had greater germination percentage and rate than nonprimed seeds, surface-dried seeds stored at 20C, or primed dried-back seeds. Dried-back primed tomato seeds had higher germination percentage than surface-dried primed seeds after 2 or 3 months of storage, with storage temperature having no effect on germination perecentage or rate. In a further study, primed surface-dried and primed dried-back seeds stored at 4 or 20C for 1.5 months in sealed containers were germinated at 15, 25, or 35C under low (-0.05 MPa) or high osmotic stress (-0.4 MPa). Primed surface-dried asparagus seeds stored at 4C, compared to nonprimed seeds, surface-dried seed stored at 20C, or primed dried-back seeds, had greater germination percentage at 15 and 35C and low osmotic stress, and higher germination rate at 15 or 25C. Primed tomato seeds had greater germination percentage than nonprimed seeds only at 35C and low osmotic stress, and higher germination rate at 15 or 25C. Storage of primed tomato seeds at 4C rather than 20C increased germination rate at 15 or 25C, and increased germination percentage at 35C and low osmotic stress. For maximal seed viability and germination rate after 1.5 to 3 months of storage, primed asparagus and tomato seeds should be stored at 4C rather than 20C; however, asparagus seeds should be surface-dried, and tomato seeds should be dried-back.

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Abstract

Metalaxyl, etridiazole, and captan were incorporated at 0, 50, 450, and 850 mg active ingredient per liter of magnesium silicate (Laponite 445) gel to ascertain fungicide efficacy in controlling damping-off [Pythium aphanidermatum (Edson) Fitzp.] in fluid-drilled ‘Heinz 1350’ tomato (Lycopersicon esculentum Mill.). Metalaxyl and etridiazole at 50 and 450 mg a.i./liter, respectively, gave percentage emergence values in infested growth media equal to those in control media. Captan at 850 mg a.i./liter gave lower percentage emergence values in Pythium-infested media than in control media. Thus, damping-off control efficacy was in the order metalaxyl > etridiazole > captan. Seedling growth reflected fungicide efficacy in controlling Pythium, since plant fresh weight and infection index values were inversely related. Fungicides incorporated in gel were nonphy to toxic.

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