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  • Author or Editor: Y. Desjardins x
  • Journal of the American Society for Horticultural Science x
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Micropropagated plantlets of Gerbera jamesonii H. Bolus ex Hook. F. `Terra Mix', Nephrolepis exaltata (L.) Schott `Florida Ruffles', and Syngonium podophyllum Schott `White Butterfly' were inoculated with two vesicular-arbuscular mycorrhizal (VAM) fungi, Glomus intraradices Schenck and Smith and G. vesiculiferum Gerderman and Trappe. They were potted in three peat-based media to determine the effects of mycorrhizal peat substrate on acclimatization and subsequent growth of micropropagated plantlets under greenhouse conditions. Symbiosis was established between the three ornamental species and VAM fungi within 4 to 8 weeks of culture in the greenhouse, but not during acclimatization. Mortality of Gerbera and Nephrolepis mycorrhizal plantlets was reduced at week 8 compared to the noninoculated control. A peat-based substrate low in P and with good aeration improved VAM fungi spread and efficiency. Mycorrhizal substrates had a long-term benefit of increasing leaf and root dry weight of Gerbera and Nephrolepis. Mycorrhizal Gerbera plants flowered significantly faster than non-mycorrhizal plants.

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The effect of CO2 enrichment (CE) and supplemental lighting (SL) on the growth of ex vitro strawberry (Fragaria × ananassa Duch.) plantlets was studied during acclimatization. Three different concentrations of CO2 [330, 900, and 1500 ppm (v/v)] and two SL treatments (0 and 150 μmol·s–1·m–2) were applied. There was no significant interaction between light and CO2 for root and leaf dry weight and leaf area. CE had no effect on these parameters in the early period following transfer but resulted in significant increases at days 20 and 30. CE had no significant influence on leaf and root relative growth rate (RGR) over the three sampling periods, but had a significant effect on net assimilation rate at a 20- to 30-day period. At the end of the experiment, 900- and 1500-ppm treatments had a significantly higher root and shoot dry weight than the 300-ppm treatment. SL resulted in increased dry weight at 10 days and even greater increases at days 20 and 30. CE was more effective than SL in stimulating root growth, whereas SL increased shoot growth significantly. There was a synergistic effect between CE and SL. The period needed to obtain plants of a similar size to an acclimatized plantlet was shortened by 15 days with 900 ppm CO2 and SL. At the end of the experiment, SL and CE at 1500 and 900 ppm increased leaf and root dry weight by a factor of 3 and 5 for ‘Honeyoye’ and ‘Kent’, respectively. These increases were less important for SL or CE used alone.

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The waiting-bed (WB) system has the potential to significantly increase the length of the strawberry (Fragaria Xananassa Duch.) production season. In the WB phase of this system the plants were deblossomed and runners were removed to stimulate the production of a multiple crowned plant. The objective of this study was to examine the influence of planting date and cultivar on yield potential and vegetative growth of the strawberry plants in the WB and cropping beds (CB). Experiments were conducted in Ontario and Quebec. Early establishment of the WB favored the production of large multicrown plants. `Kent' appeared to be the best cultivar among five tested due to the many berries produced because of good fruit set. Yield potential was not realized in late-planted CB. The highest yields per plant (273 g) were obtained in Quebec with plants from the earliest WB. Yields in CB decreased with later plantings due to stress of transplanting when air and soil temperatures were high. Berry count was identified as the yield component most affected by the later planting date of the CB. The WB system has potential for season extension in strawberry, but WB must be established early in the season to encourage the development of a plant with high yield potential.

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Effects of CaCl2 preharvest treatment on postharvest strawberry (Fragaria × ananassa) ripening and gray mold development were assessed. Two experiments were carried out in 1987 on two sites. In the first experiment, the effects of rate of application of CaCl2 and degree of fruit maturity at treatment were studied with the conventional cultivar Kent. In the second experiment, the influence of concentration and frequency of application of CaCl2 was investigated with day-neutral `Tribute'. Calcium treatment caused a significant increase in fruit and leaf Ca contents, which were closely correlated. The degree of fruit maturity at application and the frequency of treatment did not affect Ca concentration in the tissues. Several maturity criteria were measured during fruit storage in air at 4C. Anthocyanin and free-sugar contents and tissue electrical conductivity increased, while titratable acidity and firmness decreased. In both experiments, Ca treatment delayed ripening and gray mold development. The delay increased with increasing Ca concentration.

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