W.G. Pill

Growth and stress tolerance of tomato seedlings (Lycopersicon esculentum Mill.) in response to seed treatment with paclobutrazol

SUMMARY ‘Marglobe’ tomato seeds were soaked (24 h at 22°C) or matric primed (-1.0 MPa for 7 d at 22° C) in 50 mgl-1 of paclobutrazol (PB), a triazole growth retardant. Plants from these treatments and from non-treated seeds or seedlings whose shoots were sprayed with 10 mg PB l-1 at 14 days after planting (DAP) were assessed for growth and physiological responses before and after factorially combined stresses of drought (a 14 d period of drying cycles until severe wilting) or heat (4 h at 50° C) were initiated at 24 DAP in the greenhouse. At 23 DAP, shoot heights and shoot and root dry weights of plants from PB-soaked seeds or PB-sprayed plants were similar, but lower than those from non-treated or PB-primed seeds. This pre-stress PB-mediated growth suppression was associated with greater stress tolerance as revealed by greater increases in shoot and root dry weights during the 10 d post-stress recovery period. Further support for the increased stress tolerance of plants from PB-soaked seeds or PB-sprayed plants than occurred with plants from non-treated seeds or PB-primed seeds was their higher leaf xylem pressure potential, lower leaf electrolyte leakage, and lower loss of leaf total chlorophyll during the 10 d post-stress recovery period.

Seed treatments to advance greenhouse establishment of beet and chard microgreens

Summary Seed treatments to advance the establishment of table beet or chard (Beta vulgaris L.) for greenhouse microgreen production were examined. While germination percentage was little affected, appreciable germination advancement in both crops was achieved using all seed treatments of matric priming (–1 MPa at 12°C for 6 d in fine vermiculite) or various soaks (water, 20°C for 48 h; hydrogen peroxide, 0.3% at 20°C for 48 h; hydrogen chloride, 0.3 M at 20°C for 2 h; or sodium hypochlorite, 4% at 20°C for 3 h). The most pronounced seedling emergence advancement, however, was gained by germinating seeds in fine grade vermiculite and sowing the germinated seed plus vermiculite mixture. No additional advancement in seedling emergence or growth was achieved by priming or soaking the seeds in hydrogen peroxide before germinating the seeds in the vermiculite. Germinating the seeds in shallow (c 4 cm deep) vermiculite (150% initial water, c 1 seed :3 vermiculite dry weight ratio, 27°C) for 2 d (table beet) or 3 d (chard) resulted in 0.33-fold and 2.79-fold greater shoot fresh weight, respectively, at 11 d after planting than was achieved by sowing untreated seeds.

Resin-coated, controlled-release fertilizer as a pre-plant alternative to nitrogen enrichment of stem core in soilless media containing ground stem core of kenaf (Hibiscus cannabinus L.)

SummaryGround stem xylem “core” of kenaf (Hibiscus cannabinus L.) has served successfully as a component of soilless growth media, but to avoid the growth suppression probably associated with microbial immobilization of nitrogen (N) within the kenaf, media containing kenaf require N enrichment. The present study was undertaken to determine tomato plant growth in response to preplant N enrichment of peat-based kenaf media either by soaking the kenaf in N solutions (up to 15,000 mg N l–1) or by incorporation of resin-coated, controlled release fertilizer (Osmocote 14N-6P-11.6K at 3.5, 7.0 or 10.5 kg m–3) in media containing 35% to 80% volume of kenaf. All media received weekly post-transplanting solution fertilization with 0 or 300 mg N l–1 from 21N-2.2P-16.6K. Pre-plant incorporation of Osmocote at 3.5 kg m in media containing 35% to 80% kenaf in peat that received solution fertilization resulted in similar shoot dry weights of ‘Toy Boy’ tomato (Lycopersicon esculentum Mill.) at 35 d after transplanting as...

Enhanced germination of primed mericarps of parsley (Petroselinum crispum Mill. Nyman ex A.W. Hill) limited by Alternaria alternata proliferation

Summary Osmotic priming (–1.5 or –1.0 MPa for 7, 14 or 21 d at 20°C) increased germination rates of ‘Italian Dark Green’ and ‘Moss Curled’ mericarps of parsley, but increasing the duration of priming caused a linear decrease in germination percentage. Fungal colonisation, predominantly by Alternaria alternata, was associated with decreased germination percentage and reduced hypocotyl and radicle lengths. The extent of pericarp damage and fungal colonisation during priming were rated visually from scanning electron micrographs. Pericarp degradation increased from “slight” with some cuticular damage after 7 d priming, to “moderate” with some mesocarp visible, after 21 d priming. Distribution of spores and hyphae of A. alternata increased from “covering less than 1% of the surface” on non-primed mericarps, to “light and uniform” after 7 or 21 d priming. A combination pre-priming (30 min) and post-priming (5 min) mericarp soak in 0.6% (v/v) sodium hypochlorite containing 0.015% (w/v) Tween-20 surfactant controlled fungal proliferation during 7 d priming, but not 21 d priming.

Yield of greenhouse-grown tomato in substrates containing coir and parboiled rice or burnt rice hulls

ABSTRACT Substrate components produced in the sub-tropics or tropics were combined in various proportions as substrates for the greenhouse production of ‘Big Beef’ tomato. Coir was mixed with parboiled rice hulls (PBH) or burnt rice hulls (BRH) at 0, 25, 50, 75, or 100% volume. Fruit fresh weights at equal proportions of BRH or PBH in coir were similar, with the greatest fruit yields achieved with 50 to 100% coir (0 to 50% PBH or BRH). Compared to 100% coir, PBH in coir decreased substrate container capacity and increased air porosity, while BRH in coir increased container capacity and decreased the air porosity. Pre-plant fertilisation of the PBH + coir substrates (superphosphate, gypsum, trace elements, calcium nitrate, and surfactant) increased fruit yield significantly. Substrates containing 50 to 100% coir with BRH or PBH yielded greater fruit fresh weights than was achieved in in 70% BRH + 30% gravel (a typical substrate used in the Dominican Republic), and reusing the 70% BRH + 30% gravel led to a 36% increase in fruit fresh weight. Fruit fresh weights in 100% coir or 75% coir plus 25% PBH or BRH were similar to those achieved in a commercial peat-lite. Herein we report on substrates made from tropical components that perform similarly to a peat-based substrate in the production of greenhouse-grown tomatoes.