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  • Author or Editor: Paul E. Read x
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Good horticultural educators are indeed a rare breed, based on the dearth of publications cited under “Education” in Hort-Science indexes. The data presented in Tables 1 and 2 are cause for serious concern in my opinion. Furthermore, the picture becomes even more dismal when the figures are examined closely.

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The influence of the stock plant (mother plant, donor plant) has long been known to exert a profound effect on subsequent propagation capability of its propagules. Both treatments applied to the stock plant and the environment under which the stock plant is grown have a strong influence on subsequent propagation. These effects may include an increase in size or number of cuttings and improved root regeneration by cuttings taken from such stock plants. Nutrition, light, temperature, genotype, plant growth regulator applications, physical manipulations, and season of the year have all been reported to influence macropropagation efforts. Similarly, the influence of these same factors often has been reported to have a strong effect on the performance of propagated explants taken from stock plants so treated. From the early work of Kraus and Kraybill (18) in 1918, we can see that the carbohydrate: nitrogen ratio was shown to be an important factor in the rooting of tomato cuttings. Micronutrition of stock plants also has been given some attention, as exemplified by the work of Weiser and Blaney (25). Dhillon (5) also has pointed out that nutrient effects often are modified by light. Reduced light intensity has been reported to enhance the rooting of dahlia, forsythia, and weigelia (3, 19). Etiolation, or extreme light reduction, frequently has been reported to also improve rooting (9. 17). Other authors have reported that reduced stock plant light intensities can lead to better rooting of the cuttings of several species (1, 11, 21). Increases in endogenous auxin level generally are believed to occur under reduced light, thus enhancing rooting (20). Whally (26) has reviewed literature on photoperiod effects on rooting of numerous ornamental species. Keeping stock plants in a vegetative condition by the use of night interruption or day extension has enabled researchers to provide a continuous supply of cuttings (14, 15, 24). Bachelard and Stowe (2) and von Hentig (16) have reported direct effects of stock plant photoperiod on the rooting of cuttings.

Open Access

Abstract

Dipping the basal inch of cuttings in 2500 ppm succinic acid 2,2-dimethylhydiazide (SADH) solutions for 15 sec promoted rooting of carnation (Dianthus caryophyllus L.) and poinsettia (Euphorbia pulcherrima Wild). Materials such as (2-chlorethyl)trimethylammonium chloride (chlormequat), N-pyrrolidino-succinamic acid (SAPL), gibberellic acid (GA), abscisic acid (ABA), 2-chloroethylphosphonic acid (ethephon) and ethylhydrogen 1-propylphosphonate (EHPP) either decreased or had little effect on rooting.

Open Access

Abstract

This symposium is sponsored jointly by the Tissue Culture and Propagation Working Groups, with cosponsorship by ASHS Working Groups on Viticulture and Small Fruits, Citrus, and Fruit Breeding. The interest of these groups indicates the significance of this subject to so many areas of horticulture. Many professionals in both commercial and public sectors devote their efforts to, and earn their livelihood from, a dependency on clonal propagation. Most fruit crops, many nursery species and types, a significant number of floricultural crops, and several vegetables are propagated clonally (6, 7). Recently, many of these clones have been propagated commercially through various tissue-culture methods (7, 14).

Open Access

The effects of organic compounds most commonly used for orchid micropropagation and the physical condition of the medium were investigated for the development of young temperate orchid protocorms. Separate experiments were conducted with five different temperate orchid species: Dactylorhiza fuchsii, Dactylorhiza maculata, Dactylorhiza majalis, Orchis morio, and Ophrys lutea. Small 2- to 4-mm-wide protocorms were placed in baby food jars (three per jar) containing 50 ml modified FAST medium (Szendrak and R. Eszki, 1993) supplemented with one of eight treatments in a split-plot design with five replications. Both the liquid medium (gyrotary shaker, 125 rpm) and the gelled medium (8 g agar/L) were supplemented with one of the following compounds: 2 g peptone/L; 100 ml coconut water/L; 1 g casein+1 g lactalbumin/L; and 10 g glucose/L as a treatment with a defined compound. All treatments were kept in the dark at 25°C. The number of protocorms/jar were counted weekly over a 6-week-long period and the size and fresh weight of protocorms were measured at the end of the 6th week. In most cases, the liquid medium increased proliferation and the size of the protocorms. However, generally after the 4th week on liquid medium, the development of the protocorms often stopped, but it continued on the gelled medium till the end of the experimental period. The media supplemented with the undefined organic compounds showed a much better effect than the medium supplemented with glucose. Generally peptone and coconut water led to the best development of protocorms, but this varied with species. The development of protocorms into plantlets was normal in all cases.

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Axillary buds of `Valiant' grapevine (Vitis spp.) grown in vitro were transferred onto Murashige and Skoog (MS) medium supplemented with different cytokinin and auxin combinations and concentrations. It was found that culture medium caused statistically important differences in number of nodes, number of fully expanded leaves, number of multiple shoots, number of roots, and length of shoots. MS medium supplemented with 1.0 mg BA/liter in combination with 0.01 mg NAA/L was found to be the best medium for shoot growth and callus production. MS medium supplemented with the combination of 0.5 mg BA/L and 0.01 mg NAA/L was the best medium for explant rooting. The medium containing BA and NAA encouraged better shoot growth than those containing BA alone. When the concentration of BA in the medium was increased, multiple shoot proliferation and teratological structures of explants increased, but the number of small leaves and length of internode decreased. Axillary bud culture led to better shoot growth than was found for shoot apex culture. The presence of leaves positively affected shoot growth from axillary buds. Also placing the axillary buds horizontally onto the medium gave better shoot proliferation and growth than placing them vertically.

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Research was conducted in Feb. 1999 to study the effects of including silver thiosulfate (STS), gibberellic acid (GA3), or both in the forcing solution on rooting of softwood cuttings produced by forced dormant woody plant species. The cuttings were dipped for 10 s in 2000 ppm indole-3-acetic acid (IAA) or 2000 ppm indolebutyric acid (IBA). High percentages of rooting were observed in the two woody plant species examined. Root number and length of the new growth of Cornus alba and Euonymus alatus forced in a forcing solution containing the basic forcing solution treatment (8-HQC at 200 mg·L-1 + 2% sucrose), the STS treatment, or the combination treatment of STS + GA3 were not significantly different. However, treating the dormant stems of the two woody plant species examined in a forcing solution containing only GA3 led to fewer and shorter roots when compared to all other treatments. Applying either IAA or IBA to the new softwood growth led to similar root length and number for both species. This forcing solution approach provides an attractive alternative for propagating woody plants during winter months.

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Research was conducted to further modify the forcing solution system in order to expedite the propagation of woody plants, such as Spiraea canescens, Lonicera maakii, and Cornus alba. Time of immersion in solutions containing 5 mM silver thiosulfate (STS) was compared with the basic forcing solution reported by Yang and Read (1989), a solution containing 200 mg 8-hydroxyquinoline citrate per liter and 2% sucrose. Other treatments employed were gibberellic acid (GA3) 50 mg per liter for 24 h and a combination of STS and GA3 for the same amount of time. Increasing the time in STS solution up to 24 h led to higher percent budbreak and shorter time to budbreak for all the three species examined. The combination of STS and GA3 was the most effective treatment overall in reducing time of budbreak and increasing percent of budbreak. All STS treatments studied showed similar responses in shoot elongation. However, treatments with GA3 alone, and in combination with STS showed more than a doubling in shoot length compared to all STS treatments studied and the control. Implications based on SEM observations will be presented.

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