Search Results
Abstract
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.
Abstract
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.
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.
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.
A certain period of cold is needed to break bud dormancy for almost all woody species. A pre-forcing bleach soak has been demonstrated to at least partially replace this requirement (Yang and Read, 1989). Therefore, new softwood growth can be produced in the off-season. Such supple softwood growth is excellent material to be used either as explants for in vitro culture, or as cuttings for macropropagation of woody species. Further studies on pre-forcing bleach soaks were conducted to investigate optimum concentration and duration of soak, and to find the most suitable depth of bleach solution soak, in order to maximize the breaking of bud dormancy. Optimum bud break was obtained by soaking the basal 1/3 of dormant stems in 10% bleach solution for 10 minutes prior to forcing. Soaking dormant woody stems in alcohol solutions prior to placing stems in the forcing solution was also studied. The alcohol soak had negative effects on bud break of spirea, although it showed positive effects for lilac and privet.
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).
Chimeral African violets do not come true when propagated from leaf cuttings in conventional or micropropagation systems. Chimeral plants are normally propagated by rooting suckers from mother plants. Premium prices are charged for chimeral plants due to the low numbers produced.
Reports in the African violet Society Magazine indicate that chimeral plants can be started by rooting flower peduncles. However, only one or two new plants are generated from each peduncle.
Peduncle tissue was grown in vitro to produce large numbers of plants from chimeral African violets. Ratios of plants with true-to-type vs. off-type flowers varied by cultivar and tissue used. The potential use of this technology will be discussed.
A forcing solution containing 200 mg 8-hydroxyquinoline citrate per liter and 2% sucrose has enhanced availability of cutting materials by forcing dormant woody stems in the off-season. Anxins, such as IBA, included in the forcing solution promoted subsequent rooting by increasing root number per cutting and root length for privet. Inclusion of IBA in the forcing solution following the initial use of GA3 in the forcing solution counteracted the undesirable effects of GA3 on rooting and stimulated rooting after taking advantage of the favorable effects of GA3 on bud break and shoot elongation. However, the ability of IBA to counteract the negative effects of GA3 on rooting was dependent on the length of GA3 treatment. The modification of forcing solution system by sequentially including GA3 and then replacing GA3 with IBA expedited propagation of privet. Production of candidate cuttings or explants was stimulated by including GA3 in the forcing solution, and rooting of the cuttings was promoted by subsequent auxin or cytokinin inclusions in the forcing solution to replace GA3 This modified forcing solution system also proved to be a successful and efficient model for propagation of other difficult to propagate woody species.