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Steven A. Tjosvold

The atmosphere of commercial greenhouses were enriched to 1200 μl·1-1 carbon dioxide 1 hour before sunrise and maintained until ventilation was necessary to cool the greenhouse and again anytime the greenhouse vents were closed in the daytime. Enrichment was only possible, on average, for 5 daylight hours in the winter and less in the warmer months. In the first 10 month experiment, total production was not different in carbon dioxide enriched greenhouses. Stem lengths of harvested flowers were generally longer in the enriched greenhouses, particularly in the winter months. In the second 10 month experiment, total production was again not different in carbon dioxide enriched greenhouses, however, stem length was only slightly longer in the winter months. Dry weights of flower buds, stems and leaves increased slightly but only in winter months.

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Steven A. Tjosvold, Meng-Jen Wu, and Michael S. Reid

Potted miniature roses (Rosa hybrida `Belle Sunblaze') held after production in simulated home conditions performed poorly due to premature yellowing and abscission of buds and leaves, and failure of buds to open. These symptoms were accelerated when the plants were exposed to low concentrations (1 ppm) of ethylene. Spray application of 100 ppm 6-benzylaminopurine (BA) reduced yellowing, but had little effect on bud yellowing and flower opening. Application of 1 mM STS prevented the abscission of leaves and buds, although it only partly reduced leaf yellowing. A combined BA and STS treatment greatly improved the postproduction quality of rose plants, particularly if applied 1 day before harvesting.

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Martin Schochow, Steven A. Tjosvold, and Antoon T. Ploeg

Lisianthus [Eustoma grandiflorum (Raf.) Shinn.] plants were grown in soil infested with increasing densities of Meloidogyne hapla Chitwood, M. incognita (Kofoid & White) Chitwood, or M. javanica (Treub) Chitwood, root-knot nematodes. Compared to tomato plants grown in soil with the same nematode numbers and species, lisianthus had less severe root symptoms, suffered less damage, and resulted in lower nematode multiplication rates. Lisianthus was a better host for M. javanica than for M. incognita, and a poor host for M. hapla. Lisianthus shoot weights were significantly reduced after inoculation with M. javanica or M. hapla, but not after M. incognita inoculation. The number of flowers produced per lisianthus plant was reduced by all three nematode species. The results show that the root-knot nematode species that are most common in California may cause significant damage in the cut-flower production of lisianthus.

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Steven A. Tjosvold, Meng-Jen Wu, and Michael S. Reid

Potted miniature roses (Rosa × hybrids L. `Belle Sunblaze') held after production in simulated home conditions (21C, continuous fluorescent light) yellowed prematurely, flower buds and leaves abscised, and flower buds failed to open. These symptoms were accelerated when the plants were exposed to low concentrations (1 μl·liter-1) of ethylene in the absence of inhibitors. Spray application of 100 μl BA/liter reduced leaf yellowing but had no significant effect on flower opening or bud abscission. Spray application of 1 mm silver thiosulfate (STS) strongly promoted flower display but did not prevent leaf yellowing. A combined BA and STS treatment greatly improved the postproduction quality of rose plants, particularly if applied 1 day before harvest. Chemical name used: benzyladenine (BA).