Wallace G. Pill

Germination characteristics of osmotically primed and stored Impatiens seeds

Abstract Seeds of impatiens cultivar ‘Princess Bright Red’ ( Impatiens wallerana Hook. f.) were osmotically primed in −0.5, −1.0 or −1.5 MPa polyethylene glycol 8000 (PEG) at 5, 15 or 25°C for 1, 2 or 3 weeks before germination in water at 25°C. Increasing temperature during priming increased the subsequent germination rate, but priming at 25°C in −0.5 MPa PEG led to precocious germination. Priming conditions of 〈 −1.0 MPa or 〉 1 week did not benefit subsequent germination. The priming treatment selected as optimal was −1.0 MPa at 25°C for 1 week. The beneficial effects of priming were most pronounced when germination occurred during the combined stresses of reduced temperature (12.5°C) and reduced water availability (−0.5 MPa). Under these conditions, primed seeds had 80% final germination and 11.5 days to 50% germination, whereas the respective values for untreated seeds were 50% final germination and 18.1 days. Primed seeds were stored for up to 8 weeks at 25°C following 3 drying treatments (surface dried, dried back or vacuum dried). Germination percentages of primed-stored seeds were not different from those of primed-unstored seeds or of untreated seeds. Germination of dried-back and vacuum-dried seeds following 8 weeks of storage was slower than that of other stored seeds. Germination of primed-stored seeds was quicker than that of untreated seeds.

Matric and osmotic priming of Echinacea purpurea (L.) Moench seeds

Abstract Purple coneflower seeds ( Echinacea purpurea (L.) Moench) following osmotic priming in polyethylene glycol (PEG) or matric priming in expanded vermiculite had greater rate, synchrony and percentage of germination at 20° C than non-primed seeds. Osmotic or matric priming for 10 days at −0.4 MPa and 15° C resulted in higher germination rate and percentage than shorter (5 day) exposure or lower (−1.5 MPa) water potential. Seedling emergence rate, synchrony and percentage from osmotically or matrically primed seeds were similar in both cool (23–27° C day) and warm (35–40° C) glasshouse regimes. Emergence was faster from primed than from non-primed seeds in both regimes. Emergence percentage was higher (80%) from primed seeds than from non-primed seeds (50%) in the cool regime but emergence synchrony was unaffected. In the warm regime, primed seeds emerged more synchronously than non-primed seeds but emergence percentage was unaffected. Moistened vermiculite substituted for PEG solution as a priming medium for purple coneflower seeds since benefits to seed germination or seedling emergence following priming (−0.4MPa, 15° C, 10 days, darkness) in these media were similar.

Effects of hydrogel incorporation in peat‐lite on tomato growth and water relations

Abstract The effects of subirrigation and cylical (surface) irrigation on shoot growth and water stress of tomato grown in peat‐lite amended with 0, 4, 8, 12, and 16 kg Hydrogel/m were examined. While shoot growth showed a quadratic response to increasing Hydrogel rate with maximal growth occurring at the manufacturers recommended rate (8 kg/m3), growth was greater with cyclical irrigation than with subirrigation. Subirrigation generally resulted in greater plant water stress than cyclical irrigation, but with ≤ 8 kg Hydrogel/m3 this differential irrigation effect diminished temporally. Initially, each kg Hydrogel/m3 increased peat‐lite water content by 9 percent but after 31 days, this value had increased to 27 percent and 16 percent with subirrigation and cyclical irrigation, respectively. The continued hydration resulted in a bulk volume increase sufficiently large with subirrigation to cause the Hydrogel‐amended peat‐lite to overflow the pots.

Cultural practices to speed the growth of microgreen arugula (roquette; Eruca vesicaria subsp. sativa).

Summary Microgreens are salad crop shoots harvested for consumption within 10 – 20 d of seedling emergence. A series of cultural experiments was conducted with the objective of lessening the greenhouse production time, and therefore the production cost, for microgreen arugula (Eruca vesicaria subsp. sativa) grown in peat-lite (a soilless medium). Sowing seeds at a high rate (55 g m–2) resulted in a greater shoot fresh weight (FW) m–2 at 10 d after planting (DAP) than sowing at lower rates, although individual shoots were lighter. Two fertilisation regimes were examined: pre-plant incorporation of 500 – 4,000 mg N l–1 supplied as ammonium nitrate, calcium nitrate, ammonium sulphate, or urea, and/or post-emergence daily fertilisation with solutions of 21-2.2-16.6 (N-P-K) at 0, 75, or 150 mg N l–1. The two most economical fertilisation treatments to increase shoot FW m–2 were daily solution fertilisation with 150 mg N l–1, or daily solution fertilisation with 75 mg N l–1 plus a pre-plant media incorporation of 1,000 mg N l–1 from Ca(NO3)2. Irrespective of these two fertilisation treatments, pre-sowing germination (pre-germination) of seed by incubation in grade-5 exfoliated vermiculite (1.12 g seed in 157 g vermiculite) moistened with 2 gwater g–1 dry weight (DW) vermiculite for 1 d at 20°C, resulted in a 21% increase in shoot FW by 14 DAP compared to sowing non-treated seed. Pre-germinated seed showed 81.5% germination, with radicles averaging 2 mm in length at the time of sowing.

Fluid drilling as a delivery system for somatic embryo-derived plantlets of carrot (Daucus carota L.)☆

Abstract Somatic embryos and/or somatic embryo-derived plantlets (SEPs) of carrot cultivar ‘Orlando Gold’ were subjected to various treatments during either suspension culture or a subsequent incubation period in fluid-drilling gel. Conversion of SEPs in the glasshouse into plants containing primary leaves was greatest when SEPs were incubated for 1–2 weeks in hydroxyethyl cellulose fluid-drilling gel (1.67%, w/v of N-gel™) hydrated with a solution containing Murashige and Skoog salts and vitamins and 2% (w/v) sucrose. Providing 3 days of chilling at 4°C then 3 days at 25°C all under light (60 μmol m−2 s−1) during suspension culture (at the globular to torpedo stage) led to the greatest SEP growth following fluid drilling. Inclusion of either 250 mg TrubanR fungicide or 10 mg chitosan glutamate per litre of gel improved SEP conversion.

Factors Affecting the Growth of Microgreen Table Beet

There are very few reports on the production of microgreens, a new category of salad crops, the shoots of which are harvested at the seedling stage. A series of cultural studies was conducted with the objective of lessening greenhouse production time and lowering production costs of microgreen table beet (Beta vulgaris L.). Sowing seed balls at a commercially recommended rate (201 g·m−2; 11,256·seed balls·m−2) resulted in greater shoot fresh weight·m−2 at 15 days after planting than sowing seed balls at lower rates, although individual shoots were lighter. Sowing seed balls that were germinated before sowing (pregerminated) in fine-grade exfoliated vermiculite moistened with 150% water (wt. per vermiculite dry wt.) for 5 days at 20°C resulted in 26% greater shoot fresh weight·m−2 at 15 days after planting than sowing nontreated seed balls. Combining preplanting fertilization of the peat-lite with calcium nitrate at 2000 mg·L−1 of N (150 mL·L−1of medium) with daily postplanting solution fertilization with 150 mg·L−1 of N led to a further increase in shoot fresh weight·m−2 of 21% (nontreated seed balls) and 22% (pregerminated seed balls) compared to other fertilization regimes (excluding the check). Germinating, and extruding, seed balls in hydrophilic polymer (hydroxyethyl cellulose gel) advanced microgreen growth but not to the extent achieved with vermiculite as the pregermination medium. Irrespective of seed ball treatment, producing microgreens in troughs using the hydroponic nutrient film technique, compared to production in trays containing peat-lite, increased shoot fresh weight·m−2. Depending on seed ball treatment, economic yield was increased 33% to 98% by 7 days after planting and 75% to 144% by 15 days after planting. The greatest shoot fresh weight·m−2 at 15 days after planting (10.14 kg·m−2) was achieved using seed balls pregerminated in moist vermiculite and subsequent growth using the nutrient film technique.

Performance of germinated, imbibed and dry petunia seed fluid-drilled in two gels with nutrient additives

Abstract Seeds of ‘Commanche’ petunia (Petunia hybrida Vilm.) were germinated (GE) or imbibed (IM) on the surface of Laponite 445 or Natrosol 250 HHR gels prepared from 0, 0.5 or 1.0-fold Hoaglands solution. These seeds and dry seed (DS) were incorporated in the gels and extruded onto peat—vermiculite. When compared to a dry-seed control (without gels), DS in either gel without nutrient additive did not increase percentage of transplantable seedlings, but IM and GE resulted in a 32% increase. In comparing only fluid-drilled treatments, percentage of transplantable seedlings was increased by GE relative to IM in both gels, but by IM relative to DS only in Laponite. In both gels, emergence rate (T50) and uniformity (T10–90) and shoot fresh weight were influenced in the order GE > IM > DS. Increasing nutrient concentration in both gels decreased T10–90 but had no effect on T50 or shoot fresh weight. Percentage of transplantable seedlings was increased in Laponite but decreased in Natrosol with increasing gel nutrient concentration. The highest percentage of transplantable seedlings was achieved with GE in Natrosol without nutrient additive (75.4%) and in Laponite with the highest nutrient concentration (81%), each giving approximately one-half of the T50 and T10–90 values of the dry-seed control which yielded 53% transplantable seedlings.

Tomato seedling growth in peat and peat‐lite blocks amended with hydrophilic polymer

Abstract Blocks were formed from peat or peat‐lite amended with a granulated hydrophilic polymer (Viterra Agri‐gel® , potassium propenoate‐propenamide copolymer) or a binding agent (Natrosol 250 HHR® , hydroxyethyl cellulose). Blocks were subjected to slow‐release (Osmocote®) or solution fertilization and to cyclical or capillary irrigation. Tomato seedling shoot fresh weight was acceptable in peat‐lite blocks irrespective of fertilization or irrigation regime, and in peat blocks irrespective of irrigation regime if provided solution fertilization. Shoot fresh weight increased quadratically with increasing Agri‐gel incorporation rate in peat and peat‐lite blocks receiving solution fertilization, irrespective of irrigation regime. Peat blocks held more water and underwent less expansion with hydra‐tion than peat‐lite blocks. Capillary irrigation resulted in greater block stability than cyclical irrigation. Agri‐gel incorporation in blocks increased block water content and block stability. Natrosol incorpor...

Response of tomato seeds fluid-drilled in low-phosphorus growth media to phosphorus incorporation in the carrier gel

Abstract Germinated ‘Heinz 1350’ tomato seeds ( Lycopersicon esculentum Mill.) were fluid-drilled in peat-vermiculite prepared with or without 1.2 kg 0-9-0 m −3 (high-P and low-P media, respectively) using Natrosol 250HHR or Laponite 445 carrier gels containing 0, 10, 20 or 30 g l −1 of NaH 2 PO 4 , NH 4 H 2 PO 4 or KH 2 PO 4 . Percentage emergence was unaffected by P status of the growth medium and was little affected by salt species or concentration in either gel. Emergence rate, however, decreased as gel P concentration increased. Increasing gel P concentration did not increase seedling shoot dry weight in high-P media. In low-P media, however, 10–30 g l −1 of all salts in either gel, compared to 0 g l −1 , gave an average 4.2-fold increase in shoot dry weight, with 10 g NH 4 H 2 PO 4 l −1 gel yielding the greatest shoot dry weight. In a further glasshouse study, germinated tomato seeds were fluid-drilled into low-P media using Natrosol or Laponite gels containing 2700 mg P l −1 as either monobasic (Na, NH 4 , K) phosphate salts, or N + P + K salts (KH 2 PO 4 + (NH 4 ) 2 SO 4 , KH 2 PO 4 + NaNO 3 , or proprietary 10-6.6-8.3). Low percentage emergence with KH 2 PO 4 + NaNO 3 in both gels and with 10-6.6-8.3 in Laponite was associated with high gel electrical conductivity. N + P + K in gel, compared to single monobasic P-salt inclusion, did not give greater seedling growth. The cationic species associated with the phosphate did not significantly influence percentage emergence, shoot dry weight or shoot P concentration. All P-bearing gels gave greater growth and P concentration of shoots than the fluid-drilled (zero salt) control. The 22% greater shoot dry weight with Natrosol than with Laponite was not associated with increased shoot P concentration.

Performance of seeds embedded in hydroxyethyl cellulose sheets

Abstract To prepare “seed sheets”, seeds of cultivar ‘Heinz 1350’ tomato (Lycopersicon esculentum Mill.) and cultivar ‘Kewpie Orange’ celosia (Celosia cristata L.) were placed at 1.5 × 1.5 cm spacing in drying solutions of 5% (wt./vol.) hydroxyethylcellulose (HEC, Natrosol 250 LR™) plasticized with 0.35% (vol.vol.) triacetin. After planting in a peat-lite medium, emergence characteristics and seedling shoot weights from unprimed and primed seeds stored in the sheets for 4 weeks were similar to those of seeds not stored in sheets. After 4 weeks of storage in HEC sheets, primed tomato seeds (−1 MPa polyethylene glycol, 15°C, 1 week) gave earlier seedling emergence and greater seedling shoot fresh weight than unprimed seeds stored for 4 weeks in HEC sheets. Whilst 200–1600 mg N l−1 in the HEC had no effect on tomato seedling emergence or shoot fresh weight, 1600 mg N 1−1 reduced the rate and synchrony of celosia seedling emergence. “Seed sheets” prepared from HEC provided a rapid and practicable means of sowing many seeds at predetermined spacing.