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Margarita Pérez-Jiménez, Almudena Bayo-Canha, Gregorio López-Ortega, and Francisco M. del Amor

steps, all of which are crucial to the final success. However, acclimatization is not always an easy step and in many species low survival percentages are obtained ( Marin, 2003 ). Thereby, it is crucial to provide a healthy development to ensure high

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James E. Faust, Jeffrey W. Adelberg, Kelly P. Lewis, and Genhua Niu

The effects of storage temperature and shoot preparation of elephant ears (Colocasia antiquorum `Illustris') were examined to determine how to successfully store plants prior to greenhouse forcing. A series of experiments were conducted that provided storage temperatures of 4, 7, 10, 13, or 16 °C (39.2, 44.6, 50.0, 55.4, or 60.8 °F), and plants were placed into storage with the shoots uncut or cut to 3.0 cm (1.18 inches) above the surface of the growing medium. The storage duration ranged from 40 to 49 days. All plants stored at 4 or 7 °C died. Plant survival was 89% to 100% at 10 °C, while plant survival was 100% at 13 or 16 °C. Shoot emergence and plant growth was faster following storage at 13 and 16 °C, than storage at 10 °C. Storage at 16 °C resulted in leaf growth occurring during storage, which was undesirable. Removing shoots prior to storage had no effect on plant survival and performance during forcing. A fungicide drench with iprodione immediately prior to storage did not improve plant survival. This study suggests that 13 °C is near the base temperature for leaf development of elephant ears, thus the plants survive at this temperature with no growth occurring. Shoot removal prior to storage is recommended in order to optimize storage room space.

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Denis Lauzer and Claire Laberge

To update and complete a collection of wild roses in the Montreal Botanical Garden, Canada, in vitro embryo culture was used to propagate several Rosa species that are only available as seeds and difficult to germinate conventionally. Using embryo culture, it was possible to overcome seed dormancy and to rapidly increase the number of species in the collection, and this from a very limited number of seeds obtained from botanical institutions located around the world.

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J.M. Sarracino, R. Merrit, and C.K. Chin

Two foliage plant species, Leea coccinia L. and Leea rubra L., were evaluated for survival and for morphological and physiological changes in response to low light flux. Both species of Leea survived in light as low as that survived by Ficus benjamina L. Following 124 days under simulated interior lighting conditions of 5.7, 2.6, or 0.70 mol·m-2·day-1, L. coccinia, L. rubra, and F. benjamina plants grown in 92% shade had lower total fresh/dry weight, smaller leaf area, and thinner leaves than plants grown in full sun. After 124 days, plants of all three species in 92% shade were shorter, narrower, and had fewer growing points than plants in full sun. After 124 days, plants of L. coccinia grown in 92% shade contained more total chlorophyll, and more chlorophyll a and b, and they had a lower chlorophyll a: b ratio than plants from full sun. Anthocyanin content in L. rubra plants grown in 92% shade was lower than that of plants grown in full sun. Plants of F. benjamina grown in 92% shade contained more total chlorophyll and more chlorophyll a and b than plants grown in full sun.

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Pascal Nzokou and Paligwende Nikiema

The effects of three plant growth regulators (PGRs) (prohexadione–calcium, paclobutrazol, and flurprimidol) on the resistance of Fraser fir (Abies fraseri) and Colorado blue spruce (Picea pungens) to cold injuries were investigated. Treated and untreated seedlings were first allowed to harden before exposure to warm temperatures in a greenhouse. The seedlings were then subjected to an artificial freezing test to simulate the return to normal winter conditions. Chlorophyll fluorescence, relative electrolyte leakage, bud survival, and posttreatment plant survival were recorded to evaluate the effectiveness of the treatments. Results showed that treatments with paclobutrazol and flurprimidol maintained the photosynthetic ability of the plants and reduced the extent of needle cold injuries. There was no effect on bud and plant survival, possibly as a result of the timing of the PGR application. Further studies with adjustment of the timing and rates of PGR treatments are needed to validate these results.

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Dorcas K. Isutsa, Marvin P. Pritts, and Kenneth W. Mudge

A protocol is presented that enables a propagator to produce field-sized blueberry transplants within 6 months of obtaining microshoots from tissue culture. The protocol involves subjecting microshoots to ex vitro rooting in a fog chamber under 100 μmol·m–2·s–1 photosynthetic photon flux for 7 weeks, transferring plants to a fog tunnel for 2 weeks, then to a greenhouse for 7 more weeks. Plant survival and rooting of cultivars Berkeley (Vaccinium corymbosum L.) and Northsky (Vaccinium angustifolium ×corymbosum) were near 100% under these conditions. Plantlets in fog chambers receiving 100 μmol·m–2·s–1 grew rapidly, while those at lower irradiance levels grew more slowly, and supplemental CO2 enhanced growth only at 50 μmol·m–2·s–1. Growth rates slowed when plants were moved into the fog tunnel; but by the end of 16 weeks, plants that were under high irradiance in the fog chamber had root systems that were 15 to 30 times larger than plants under low irradiance. Within 6 months, these plants were 30 to 60 cm tall and suitable for field planting.

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Laura A. Dellevigne, Jeffrey W. Adelberg, and Peter Vergano

Three-dimensional polypropylene enclosures have been fabricated for the in vitro culture and ex vitro growth of Cattleya orchid propagules. The enclosures consist of: 1) microporous polypropylene membrane for nutrient transfer between liquid media and the growing tissue. 2) molded polypropylene side wall sized for growth of Cattleya orchid plants and flanged to allow heat seals with membranes, and 3) polypropylene membrane(s) top member for light and gaseous transmission. Three commercial clones of Cattleya have been sealed into these enclosures and grown for eight months on unmended MS medium. Contaminated liquid media was effectively isolated from the propagules within the sealed enclosures, and following a bleach treatment with sterile rinses, propagules were returned to aseptic culture. Greenhouse growth of plant tissues in these enclosures will be discussed. Optimization for growth of Cattleya has begun with studies of gas, light and temperature regimes within the sealed enclosures and a comparison of growth on two different nutrient formulations.

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Ribo Deng and Danielle J. Donnelly

Micropropagated `Festival' red raspberry (Rubus idaeus L.) shoots were rooted in specially constructed plexiglass chambers in ambient (340 ± 20 ppm) or enriched (1500 ±50 ppm) CO2 conditions on a medium containing 0, 10, 20, or 30 g sucrose/liter. Plantlet growth and leaf 14CO2 fixation rates were evaluated before and 4 weeks after ex vitro transplantation. In vitro CO2 enrichment promoted in vitro hardening; it increased root count and length, plantlet fresh weight, and photosynthetic capacity but did not affect other variables such as plantlet height, dry weight, or leaf count and area. No residual effects of in vitro CO2 enrichment were observed on 4-week-old transplants. Sucrose in the medium promoted plantlet growth but depressed photosynthesis and reduced in vitro hardening. Photoautotrophic plantlets were obtained on sucrose-free rooting medium under ambient and enriched CO2 conditions and they performed better ex vitro than mixotrophi plantlets grown with sucrose. Root hairs were more abundant and longer on root tips of photoautotrophic plantlets than on mixotrophic plantlets. The maximum CO2 uptake rate of plantlet leaves was 52% that of greenhouse control plant leaves. This did not change in the persistent leaves up to 4 weeks after ex vitro transplantation. The photosynthetic ability of persistent and new leaves of 4-week-old ex vitro transplants related neither to in vitro CO2 nor medium sucrose concentration. Consecutive new leaves of transplants took up more CO2 than persistent leaves. The third new leaf of transplants had photosynthetic rates up to 90% that of greenhouse control plant leaves. These results indicate that in vitro CO2 enrichment was beneficial to in vitro hardening and that sucrose may be reduced substantially or eliminated from red raspberry rooting medium when CO2 enrichment is used.

Open access

Doina Clapa, Claudiu Bunea, Orsolya Borsai, Adela Pintea, Monica Hârța, Răzvan Ştefan, and Alexandru Fira

shoots, photosynthetic pigment content of the leaves, and, last but not least, rooting and acclimatization rates. Materials and Methods Plant material and culture conditions. This research was carried out in the Life Science Institute of University of