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William N. MacDonald, M. James Tsujita and Theo J. Blom

Chrysanthemum morifolium Ramat. cv. `Yellow Favor' was grown single stem in 10cm pots on an ebb and flow benching system. A 2×2 factorial design was employed with 2 sources of N (100 NO3 and 50 NO3 :50 NH4 +), delivered at 18 mM, and 2 quantities of N supplied, (200 mg and 400 mg), with 200 mg supplied by wk 3 and 400 mg supplied by wk 5. Plants were harvested at two wk intervals, separated into leaves, stems plus petioles and inflorescence (when developed) and analyzed for total and NO3 - N, with reduced N being estimated as the difference between these two values. Plant tissue (leaves and stems plus petioles) NO3 - levels showed similar trends for the 200 and 400 mg N supply, with a maximum at the 4th to 6th wk. At flowering, (wk 10) significant tissue NO3 - levels were found only in plants supplied 400 mg of N. Plants supplied with 50:50 NH4 +: NO3 - initially had significantly greater reduced N and leaf area than NO3 - supplied plants, although differences diminished towards flowering. During floral development (wk 8 to 10), at which time no additional N was accumulated by the plant, significant amounts of reduced N was remobilized from the stem plus petioles and leaves to the developing inflorescence.

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William N. MacDonald, M. James Tsujita and Theo J. Blom

Excessive supply of fertilizer N can lead to inefficient use of supplied N and consequently affect plant quality. Reduction of supplied fertilizer N can possibly increase plant N usage efficiency and improve quality. Chrysanthemum morifolium Ramat. cv. `Yellow Favor' was grown single stem in 10 cm pots on an ebb and flow benching system. All plants received 18.5 mM NO3 - N, until the mid point of this ten wk crop, at which time the following NO3 - concentrations (mM) were employed: 18.5, 15.5, 12.5, 9.5, clear water and clear water alternating with 18.5 mM NO3 -. Plants were harvested at two wk intervals, cut in half and separated into leaves, stems plus petioles and inflorescence (when developed). Plant tissue from the lower half of the plant was analyzed for total and NO3 - N, with reduced N being estimated as the difference between these two values. All growth parameters measured did not significantly differ, although termination of N fertilization (clear water) and reduction of NO3 - level to 9.5 mM significantly reduced NO3 - levels in the lower leaf and stem plus petioles, with a concomitant increase in reduced N in these tissues, over the 6-10 wk period. Total amounts of N accumulated in plant tissues analyzed did not differ significantly at flowering.

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Theo J. Blom, M.J. Tsujita and Glen L. Roberts

Potted plants of Lilium longiflorum Thunb. cvs. `Ace' and `Nellie White' were grown either under an ambient photoperiod (APP) or under an 8-hour photoperiod (8PP) in a greenhouse. The latter photoperiod was achieved by pulling black cloth over the plants at 1615HR and removing the cloth at 0615HR each day, from emergence to flowering. Within each photoperiod, ambient light intensity was reduced by 0, 20, 40 or 60% using various shade cloths permanently suspended above the plants. Heating was set at 20/16C for the dark/light period, respectively. Plant height, determined from the rim of pot to the top of plant, was 25% lower under 8PP compared to APP for both cultivars. Plant height of `Ace' and `Nellie White' increased by 1.5 mm and 2.5 mm, respectively, per 1% light reduction.

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Theo Blom, David Kerec, Wayne Brown and Dave Kristie

Potted greenhouse-forced `Nellie White' Easter lilies (Lilium longiflorum Thunb.) were irrigated from emergence with water at 2, 5, 8, 11, or 15 °C either onto the shoot apex (overhead) or onto the substrate for a 0, 2-, 4-, 6-, 8-, 10-, or 12-week period. Control treatment was at 18 °C, either overhead or on substrate. When irrigation water was applied overhead for the entire period between emergence and flowering (12 weeks), plant height increased linearly with the temperature of irrigation water (1.75 cm/°C). As the period of application with cold water increased from 0 to 12 weeks, plant height decreased both in a linear and a quadratic manner. Forcing time was negatively correlated with height with the shortest plants delayed by 3 to 6 days. Water temperature did not affect bud abortion or the number of yellow leaves. Irrigation water temperature had no effect on plant parameters when applied directly on the substrate.

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Lisa J. Skog*, Theo Blom, Wayne Brown, Dennis Murr and George Chu

Ozone treatment has many advantages for control of fungal diseases. There are no residue concerns, no registration is required, and it is non-specific, therefore potentially effective against a broad spectrum of pathogens. However, ozone is known to cause plant damage. There is little information available on either the ozone tolerance of floriculture crops or the levels required to kill plant pathogens under commercial conditions. Nine floriculture crops (begonia, petunia, Impatiens, Kalanchoe, pot roses, pot chrysanthemums, lilies, snapdragons and Alstroemeria) were subjected to increasing levels of ozone. Trials were conducted at 5 and 20 °C (90% to 95% RH) and ozone exposure was for 4 days for either 10 hours per day (simulating night treatment) or for 10 minutes every hour. Damage was assessed immediately after treatment and after an additional 3 days at room temperature in ozone-free air. Trials were terminated for the crop when an unacceptable level of damage was observed. Trials to determine the lethal dose for actively growing pathogens (Alternaria alternata, Alternaria zinniae and Botrytis cinerea) and fungal spores were conducted under identical conditions. Ozone tolerance varied with plant type and ranged between <0.2 and 3ppm. Generally, the crops surveyed were more susceptible to ozone damage at the low temperature. As a group, the bedding plants were the least tolerant. Fungal spores were killed at treatment levels between 0.8 and 2 ppm ozone. The actively growing fungal mycelium was still viable at 3 ppm ozone when the trial had to be terminated due to ozone-induced structural damage in the treatment chambers. Under the trial conditions, only the Kalanchoe would be able to tolerate the high levels of ozone required to kill the fungal spores.

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Wayne Brown, Theo J. Blom, George C.L. Chu, Wei Tang Liu and Lisa Skog

The sensitivity of easter lilies (Lilium longiflorum) to either ethylene or methane (products of incomplete burning in gas-fired unit heaters) was tested during rooting [3 weeks at 18 °C (65 °F)], vernalization [6 weeks at 6 °C (43 °F)] and subsequent greenhouse forcing (15 weeks at 18 °C). Starting at planting, easter lilies were exposed for one of seven consecutive 3-week periods (short-term), or for 0, 3, 6, 9, 12, 15, 18, or 21 weeks starting at planting (long-term) to either ethylene or methane at an average concentration of 2.4 and 2.5 μL·L-1(ppm), respectively. Short- or long-term exposure to ethylene during rooting and vernalization had no effect on the number of buds, leaves, or plant height but increased the number of days to flower. Short-term exposure within 6 weeks after vernalization reduced the number of buds by 1 bud/plant compared to the control (no ethylene exposure). However, extensive bud abortion occurred when plants were exposed to ethylene during the flower development phase. Long-term exposure to ethylene from planting until after the flower initiation period resulted in only two to three buds being initiated, while continued long-term exposure until flowering caused all flower buds to abort. Short-term exposure to methane at any time had no effect on leaf yellowing, bud number, bud abortion, or height and had only a marginal effect on production time. Long-term exposure to methane from planting until the end of vernalization increased both the number of buds, leaves and height without affecting forcing time, leaf yellowing or bud abortion.

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John Watson, François Hébert, Eric M. Lyons, Theo Blom and Katerina S. Jordan

Two complementary greenhouse studies were conducted to examine the effects of different root zones and fertilization regimes on ‘SR7200' velvet bentgrass (Agrostis canina L.) and L-93 creeping bentgrass (Agrostis stolonifera L.). In the first study, in which only velvet bentgrass was studied, peat content in the root zone mixture contributed significantly to initial establishment of this species and high seeding rates increased cumulative shoot dry weight early in establishment but became less significant as the turfgrass matured. Higher phosphorus rates contributed to increased cumulative shoot dry weight over the first 4 weeks of the experiment. Nitrogen rate was the most significant factor positively affecting both cumulative shoot dry weight and turfgrass quality. In the second experiment with both velvet bentgrass and creeping bentgrass, nitrogen rate significantly increased turfgrass quality when measured at Week 5, halfway through the experiment. Over time, however, turf growth and quality were negatively impacted in both species with increasing nitrogen rates. Root zone composition had a significant effect on initial establishment of both bentgrasses with greater peat content leading to higher quality early on. Cumulative shoot dry weight increased with increasing nitrogen rate but at higher rates, there was a concomitant decrease in root production.