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- Author or Editor: Blanche Dansereau x
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.
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.
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.
Seeds of Matthiola incana `Pink Appleblossom' and `Miracle Crimson'(stock) and Godetia Whitneyi `Grace Rose Pink'(godetia) were sown into 200 unit plug trays containing Pro-mix. Seedlings having 4 to 6 true leaves, were transplanted into ground beds containing a substrate composed of 40% sand, 45% loam soil and 15% peat moss (vol/vol). Stocks were planted at densities of 60 et 90 plants/m2 and godetias at 20, 30, 40 and 60 plants/m2. Plants were grown under ambient light conditions or a photosynthetic photon flux (PPF) of 60 μmol m-2s-1. After seedling stage, air temperatures were maintained at 18°C (day) and 13°C.(night). During the production cycles of fall-winter 1991 and 1992, a supplemental PPF reduced total production time by 26 et 27 days respectively. Supplemental light caused a reduction of stem length. Planting density did not effect the variables measured. With godetia, the supplemental light treatment significantly increased the number of saleable stems. Marketable yield increases were not proportional to higher planting densities.
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.
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.
The general objective of this project is to study the impact of pre-harvest growth conditions (supplementary lighting; HPS, MH: fertilization on the biochemistry and post-harvest quality of greenhouse roses. On January 25, 1991, 288 plants (Rosa × hybrida: `Royalty', `After Glow' and `Obsession') 3X caliber were planted in pots. A split-split plot experimental design made up of four blocks was used. Light treatments (3) were in main plot while fertilization (2) and cultivars (3 cultivars; 4 plants per cultivar) were in sub-plots and sub-sub-plots respectively. The two fertilization regimes used had respectively a nitrogen potassium ratio of 150N:300K ppm (F1) and 300N:300K ppm (F2). Three light treatments (ambient light conditions (control), and ambient light conditions + PPF of 100 μmolm-2 s-1 supplied by 400 W HPS and MH lamps) were compared. Since the beginning of this experiment 14 431 flowering stems have been harvested. Only the results obtained with `Royalty' and `After Glow' will be presented for the following harvest periods; (1) October 6 to December 6, 1991; (2) January 30 to April 22, 1992. Yields were significantly affected by light and/or fertilization regardless of cultivar. Preliminary results indicate that stems harvested from HPS and MH light treatments combined to fertilization regime F1 had a longer vase life than those grown with F2. Preliminary results indicate that HPS lamps significantly increased vase life compared to MH. The level of ABA was higher under MH then under HPS lamps at to and this was similar for all cultivars. Furthermore, when supplemental light was combined to the F1 fertilization a lower level of ABA was obtained. Low levels of ABA are correlated to longer vase life expectancy.
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.