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irrigating plants based on water requirements, water use could be reduced, and plants may be acclimated for drought tolerance in the landscape ( Kozlowski and Pallardy, 2002 ). Roses ( Rosa hybrida L.) are some of the most popular garden plants in the world

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Abstract

Vase life and floral characteristics were studied for Rosa hybrida (cvs. Forever Yours, Briarcliff Supreme, Red Garnette, and Rose Elf) flowers grown in atmospheres containing 300 ± 200, 1000 ± 300, and 2000 ± 500 ppm CO2 for at least half of the daylight hours. Only ‘Red Garnette’ flowers grown in CO2-supplemented air had significantly longer vase life (one-half day) than those produced in normal atmospheres.

Open Access

The postharvest quality of miniature pot roses is limited by bud abscission and premature flower senescence. Rosa hybrida `Victory Parade' plants were treated with ethephon to study their sensitivity to ethylene and with silver thiosulfate (STS) to investigate its inhibitory effects on ethylene action. Bud abscission and flower senescence were promoted by spraying plants with ethephon, and the longevity of individual flowers and whole plants was reduced. All STS concentrations (0.4, 0.8, 1.2, 1.6 mM improved postharvest keeping quality. Bud abscission and flower senescence were decreased and the longevity of flowers and whole plants was improved by applying STS. Chemical name used: 2-chloroethylphosphonic acid (ethephon).

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Rosa × hybrida `Meijikatar' plants were fertilized on weekdays with Hoagland's solution at 100, 200, or 300 mg·liter-1 nitrogen. Prior to simulated shipping, plants were treated with benzyladenine at 0, 25, 50, or 100 mg a.i.·liter-1. Plants were subsequently paper sleeved and stored in cardboard boxes in darkness at 16 C for 5 days.

On the day of harvest, plant height and number of flowers per plant were not affected by production nitrogen level. After removal from simulated shipping, total chlorophyll was increased in the lower leaves of plants grown at higher nitrogen rates and treated with higher rates of benzyladenine. Three and five days after removal from simulated shipping, the least percent leaf chlorosis was observed on plants treated with higher rates of cytokinin, but there was no effect of production nitrogen regime.

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Rosa × hybrida `Meijikatar' plants were fertilized on weekdays with Hoagland's solution at 100, 200, or 300 mg·liter-1 nitrogen. Prior to simulated shipping, plants were treated with benzyladenine at 0, 25, 50, or 100 mg a.i.·liter-1. Plants were subsequently paper sleeved and stored in cardboard boxes in darkness at 16 C for 5 days.

On the day of harvest, plant height and number of flowers per plant were not affected by production nitrogen level. After removal from simulated shipping, total chlorophyll was increased in the lower leaves of plants grown at higher nitrogen rates and treated with higher rates of benzyladenine. Three and five days after removal from simulated shipping, the least percent leaf chlorosis was observed on plants treated with higher rates of cytokinin, but there was no effect of production nitrogen regime.

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The growth of Rosa × hybrida and Exacum affine under different spectral filters was evaluated. Three filters that altered light quality were developed. One, a red textile dye, filtered out much of the blue/green portion of the light spectrum but did not change far-red to red (FR/R) light ratio. Another, a blue textile dye, raised FR/R by filtering out a portion of red light. The third, a salt (copper sulfate) lowered FR/R by filtering out a greater portion of far-red than red light. Two controls were used that did not alter light quality. The filters were installed in specally built growth chambers. Photosynthetic Photon Flux Density (PPFD) was adjusted to equal values in each chamber.

Plants of both species were significantly shorter and had higher leaf chlorophyll, when grown under the low FR/R filter.

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Abstract

Four Rosa hybrida cultivars were grown in 100 to 500, 700 to 1300, and 1500 to 2500 ppm CO2 atmospheres for at least half the daylight hours from November to May. Production was studied continually for 24 months.

Numbers of flowering stems and lateral buds, fresh weight, and stem length were greater in CO2 supplemented atmospheres on hybrid tea and floribunda roses. Non-flowering percentages were lower for floribundas in CO2 enriched atmospheres. Greater leaf abscission and less root development were noted for hybrid tea and floribunda roses in 1500 to 2500 ppm CO2. Higher yields in non-CO2 supplementation periods (May to October) largely reflected growing conditions rather than CO2 effects.

Open Access

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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Abstract

The relationship between Botrytis cinerea inoculum concentration and Botrytis blight on Rosa hybrida flowers from production greenhouses was monitored in the fall of 1985 and 1986 and winter of 1986 and 1987 under laboratory conditions. ‘Golden Wave’ rose flowers were inoculated with 0 to 104 conidia per milliliter and stored in incubation chambers at ≥95% RH and 21°C. Disease severity was quantified by the number of lesions per flower 48 hr after inoculation. The relationship between inoculum concentration and disease severity was linear; the coefficient of determination ranged from 0.87 to 0.99. The slope of the inoculum concentration–disease severity relationship was used to quantify susceptibility, which ranged from 0.006 to 0.035. Slopes were significantly greater with roses produced in December, January, and February (0.018 to 0.035) than those produced in October or November (0.006 to 0.013). Susceptibility of the flowers to B. cinerea was correlated linearly (r = 0.98) and inversely to the overall mean vapor pressure deficit from 0800 to 1900 hr for the 5-week growth period before harvest.

Open Access

A central composite rotatable design was used to estimate quadratic equations describing the relationship of irradiance, as measured by photosynthetic photon flux (PPF), and day (DT) and night (NT) temperatures to the growth and development of Rosa hybrida L. in controlled environments. Plants were subjected to 15 treatment combinations of the PPF, DT, and NT according to the coding of the design matrix. Day and night length were each 12 hours. Environmental factor ranges were chosen to include conditions representative of winter and spring commercial greenhouse production environments in the Midwestern United States. After an initial hard pinch, 11 plant growth characteristics were measured every 10 days and at flowering. Four plant characteristics were recorded to describe flower bud development. Response surface equations were displayed as three-dimensional plots, with DT and NT as the base axes and the plant character on the z-axis while PPF was held constant. Response surfaces illustrated the plant response to interactions of DT and NT, while comparisons between plots at different PPF showed the overall effect of PPF. Canonical analysis of all regression models revealed the stationary point and general shape of the response surface. All stationary points of the significant models were located outside the original design space, and all but one surface was a saddle shape. Both the plots and analysis showed greater stem diameter, as well as higher fresh and dry weights of stems, leaves, and flower buds to occur at flowering under combinations of low DT (≤ 17C) and low NT (≤ 14C). However, low DT and NT delayed both visible bud formation and development to flowering. Increased PPF increased overall flower stem quality by increasing stem diameter and the fresh and dry weights of all plant parts at flowering, as well as decreased time until visible bud formation and flowering. These results summarize measured development at flowering when the environment was kept constant throughout the entire plant growth cycle.

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