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  • Author or Editor: Troy T. Meinke x
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Two-year-old Rosa hybrida L. `Royalty', `Emblem', and `Samantha' plants were pinched 20 Oct. and 28 Dec. 1992 for Christmas and Valentine's Day crops. At 10 and 25 days after pinch, and at flowering, 5 shoots from each bench location were destructively sampled for leaf (node) number, stem diameter, stem length, and fresh and dry weights of stem, leaves, and flower bud. Time to visible bud, to color, and to flower from pinch were also recorded.

Results were tabulated; an analysis of variance showed that the three rose cultivars produced flowers which were not significantly different within crops but were different between seasonal crops. The Christmas `Royalty' crop produced more flowers (but also more blind shoots) than did the Valentine's Day crop. Days to flower, stem diameters, and stem lengths were similar within and between crops for all cultivars. Total fresh and dry weights for all three cultivars tended to be greater for the Valentine's Day crop than for the Christmas crop. The seasonal photosynthetic photon flux (PPF) variation may account for these differences.

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The computer simulation model ROSESIM is based on `Royalty' rose (Rosa hybrida L.) growth response to 15 unique treatment combinations of photosynthetic photon flux (PPF), day temperature (DT), and night temperature (NT) under constant growth chamber conditions. Environmental factors are assumed constant over an entire day, but set points may vary over the duration of the crop. Anticipated values for factors may be read from an ASCII file, allowing a variety of strategies to be modeled and compared.

A Valentine's Day crop senario compared 2 management strategies for crop development time and flower quality: [1] constant 24/17.1 DT/NT for the entire crop, or [2] 15 days warm 30/20C DT/NT to promote bud break, 10 days 20/15C DT/NT to promote stem caliper and leaf size, 10 days 25/18C DT/NT to promote bud development, and remaining time to flower 20/15C DT/NT to enhance flower size and color. PPF was increased gradually over crop time as would occur naturally for Dec. to Feb. Strategy [2] had longer stems (63 vs. 50 cm), similar stem and leaf dry weights, but less flower bud dry weight (1.0 vs. 1.6 g), while flowering 2 days earlier (41 vs. 43 days after pinch). c:\pm4\ash94h.pm 4

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