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Blanche Dansereau

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Serge Gagnon and Blanche Dansereau

Geranium seedlings (Pelargonium ×hortorum Bailey `Smash Hit Red') were given various cold pretreatments (CP) to obtain more rapid adaptation to constant or split-night temperature regimes. The six following CP were used: either 13C or 17/13C for 5, 10, or 15 days. The effect of these CP given at seedling stage was compared with that of control plants held at 17C at night. The CP did not significantly increase the time to first visible flower buds or to anthesis. The number of flowering stems, plant height, shoot dry weight, and leaf area of control plants were not significantly different from plants receiving CP.

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Blanche Dansereau and André Gosselin

The CRH consists of 20 professors and researchers as well as more than 50 graduate students enrolled at the master or doctorate level in the various departments of the Faculty of Agriculture and Food. The scientific program of the CRH is articulated around the theme of quality and availability of Quebec horticultural products. This multi-disciplinary program comprises: production systems, plant pathology, in vitro culture and somatic hybridization, bio-climatology, and engineering of these processes as well as post-harvest technology and marketing of horticultural products. Our goals are evidently to improve production systems but they are also aimed at the quality and innocuity of horticultural products as well as using environment-friendly technologies.

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Serge Gagnon and Blanche Dansereau

Our purpose was to determine growth regulators rate effects on growth and development of aster Callistephus chinensis. During Spring 1993 and 1994, six aster cultivars were sown into 200-unit plug trays containing Pro-Mix PGX. Seedlings were transplanted into 10-cm pots containing Pro-Mix. Two weeks after transplanting, seedlings were sprayed with chlormequat chloride (CCC) at 750 or 1500 ppm and were compared to nontreated plants. A second application was applied 2 weeks later. Growth and development of asters were affected differently depending on cultivars and experimental season. During Spring 1994, a CCC treatment of 750 and 1500 ppm significantly reduced height and width of Dwarf Carpet Mix and Dwarf Spider Mix without affecting the number of flowers and total production time compared to nontreated plants. Growth regulator treatments had no effect on height and width of `Milady Mix' and `Starlight Rose'. However, the 750 ppm CCC treatment reduced the number of flowers produced by these two cultivars. Results obtained in 1993 also are presented.

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Claudine Ménard and Blanche Dansereau

The general objective of this project was to study the impact of preharvest growth conditions [supplementary lighting as high-pressure sodium (HPS) or metal halide (MH) lights, and fertilization] on the postharvest quality of greenhouse roses. On 25 Jan. 1991, 288 plants (Rosa × hybrida `Royalty', `After-Glow', and `Obsession') of 3× caliber were planted in pots. A split-split plot experimental design made up of four blocks was used. Light treatments (three) were main plots while fertilization (two) and cultivars (three cultivars; four plants per cultivar) were subplots and sub-sub-plots, respectively. The two fertilization regimes used had respective N: K (in ppm) ratios of 150 N: 300 K (F1) and 300 N: 300 K (F2). Three light treatments [ambient light conditions (control) and ambient light conditions + PPF of 100 μmol·m-2·s-1 supplied by 400-W HPS or MH lamps] were compared. Yields were significantly affected by supplemental light treatments, fertilization, or both regardless of cultivars. Results indicate that stems harvested from HPS and MH light treatments combined with fertilization F1 had a longer vase life than those grown with F2. HPS lamps significantly increased vase life compared to MH. The level of abscisic acid (ABA) was higher under MH than under HPS lamps at time zero (T0), and this was similar for all cultivars. Furthermore, when supplemental light was combined with the F1 fertilization, a lower ABA level was obtained. Low ABA levels were correlated to longer vase life expectancy.

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Blanche Dansereau and Gagnon Serge

The first study was undertaken during fall 1989 and the second in winter 1990 using Callistephus chinensis `Pink Carpet', and Calceolaria herbeohybrida `Anytime mixture' seedlings. In both experiments, four photosynthetic photon flux levels were used; 30, 60, 90 and 120 mmol m-2 s-1 to obtain a 16 hr photoperiod. All lighting treatments were provided by HPS lamps (400 W) and compared to natural light condition (control). The utilisation of this electrotechnology not only increased vegetative growth but also reproductive development which resulted in shortening production time. Flower number was also greatly enhanced. Differences measured between control plants and those having received a supplementary light treatment were greater during fall 1989 than winter 1990 study.

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Dansereau Blanche and Charest Pierre-Mathieu

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Fabienne Gauthier, Blanche Dansereau and Serge Gagnon

During Winter 1994, seedlings of Impatiens wallerana `Accent Coral' and Pelargonium ×hortorum `Orbit Hot Pink' were grown in commercial substrate (Pro-Mix BX) or in one of the 24 substrates composed of six organic residues (composted water-treated sludge, forestry compost, fresh or composted used peat extracted by a biofilter during treatment of municipal water, and fresh or composted paper sludge). These residues were incorporated with peatmoss and perlite at 5%, 10%, 25%, and 40% per volume to obtain the 24 substrate combinations. Plants were watered and fertilized by flooding of ebb-and-flow benches. Growth measurements (growth index, top and root dry weight, number of flowers and buds, visual quality) varied considerably depending on the percentage of residue incorporated into the substrates. Moreover, substrates containing 40% of organic residues are not recommended for production of impatiens or geraniums.

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Fabienne Gauthier, Blanche Dansereau and Marie-Josee Lambert

During Fall 1995–Winter 1996, rooted cuttings of eight Rhododendron Simsii cultivars—Dorothy Gish, Jacinth, Paloma, White Gish, Friedhelm Scherrer, Gloria, Helmut Vogel, and Inga were transplanted July 1995 into 10.5-cm pots. A treatment consisted of one, two or three cuttings per pot. Cuttings were pinched either mechanically using a hedge clipper (control) or chemically with Off-Shoot-O at rates of 63.5 or 111.1 mL·L–1 of water or with Atrimmec at 20 mL·L–1 of water. Pinching treatments were repeated three times during the experimental period. New secondary shoots developed more rapidly after a mechanical pinch than after a chemical pinch. Moreover, greater foliage damage was observed on plants pinched with Off-Shoot-O. Growth measurements (height and diameter of plants, top dry mass, number of days to reach anthesis and visual quality) will be presented.

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Marie-Josee Lambert, Blanche Dansereau and Fabienne Gauthier

During Spring–Summer 1995, cuttings of eight Rhododendron simsii cultivars `Dorothy Gish', `Jacinth', `Paloma', `White Gish', `Friedhelm Scherrer', `Gloria', `Helmut Vogel', and `Inga' were rooted using two substrates combined with or without (control) four rooting hormone treatments. The rooting substrate was composed of either pure peat moss or 80% peatmoss and 20% perlite. The basal end of cuttings were dipped into one of the four hormone treatments: IBA (Stim-Root powder) at 4000 and 8000 ppm, or IBA (liquid Stim-Root) at 5000 and 10,000 ppm. This experiment was repeated in Fall 1995 and in Winter 1996 to determine the effect of seasonal period on rooting. Spring is the optimal period for rooting the cultivars used in this study. Highest percentage of rooting was obtained with cultivars `Helmut Vogel', `Inga', `Jacinth', and `Paloma'. Dry mass of cultivars propagated using liquid formulation was significantly increased during this period. Substrates did not significantly effect rooting percentage and quality and dry root mass.