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Abstract
Cyathea dregei (Alsophila dregei) Kunze, is a tree fern indigenous to Southern Africa. Due to its popularity for landscape gardens and water features, this species has been over-exploited from the wild and currently is classified as a protected plant. For this reason, attempts were made to multiply this plant by partial tissue culture (2). This simple system was adopted because it eliminates the multiple stages of culture recommended by Murashige (4), but nevertheless allows the production of large numbers of pathogen-free sporophytes (2).
Abstract
Multiple adventitious buds were induced on corms and corm-derived primary calluses of Ixia flexuosa L. cultured on Murashige and Skoog (MS) medium supplemented with 5 or 10 µm BA. Buds developed into shoots, nearly half of which rooted in the absence of an auxin. Root formation was increased to 80% with the addition of 2.5 or 5 µm NAA to the MS medium. Almost two-thirds of the plantlets survived hardening in a mistbed. Thidiazuron at 0.1 or 1.0 mg·liter−1 also induced adventitious buds on corm explants, but these buds were less vigorous than those produced with BA. Chemical names used: N-phenylmethyI)-1H-purin-6-amine (BA); 1-naphthaleneacetic acid (NAA); N-phenyl-N'-1,2,3-thiadiazol-5-ylurea (thidiazuron).
Abstract
In South Africa, the indigenous cycads comprise 28 species of Encephalartos (Za-miaceae) and Stangeria eriopus (Kunze) Baillard (3), the latter species being the sole representative of the Stangeriaceae. Present cycad populations are under severe pressure from combined effects of agricultural and urban development, exploitation by the tribal “medicine-men”, activities of plant collectors, and demands from scientific and educational institutions. In addition, the relatively slow growth rate, limited potential for vegetative propagation, and the restricted supply of viable seed further exacerbate the delicate conservation status of these dioecious plants (2).
Abstract
A commercially available seaweed concentrate (Kelpak 66) was applied to nutrient-stressed plants of cucumber (Cucumis sativa L. cv. Pepinova) as a root dip at transplant or as a weekly foliar spray. Overall plant dry mass was increased by the seaweed treatment. Those plants receiving higher levels of seaweed treatment showed greatly increased root growth.
Abstract
Dierama latifolium N.E. Br. was propagated in vitro using corm cultures. Shoots were induced from corm explants when grown on solidified Murashige and Skoog (MS) medium supplemented with 30 g/liter sucrose, 100 mg/liter meso-inositol, and 0 or 0.5 mg/liter NAA. Shoot proliferation was not improved by the addition of BA to the initial culture medium. Multiple shoots were induced by transferring those produced in vitro, to a modified MS medium supplemented with 0.5 or 1.0 mg/liter BA. Rooting of these shoots was induced by subculturing single excised shoots, 5-10 mm in height, either a hormone-free basal medium or a BM supplemented with 0.5 or 1.0 mg/liter NAA. Utilizing this technique, about 90 plants could be produced from a single corm within 12 months. Chemical names used: 1-napthalenacetic acid (NAA); N-(phenylmethyl)-1H-purin-6-amine(BA).
Two cold-tolerant species (Eucalyptus macarthurii Deane et Maiden and E. smithii R.T. Baker), a cold-tolerant hybrid (E. macarthurii×E. grandis Hill ex Maiden), and E. saligna Sm. were propagated in vitro from nodal explants collected from field-grown seedlings and from clonal hedges. Shoot growth was initiated on modified Murashige and Skoog (MS) medium containing BA at 0.1 mg·liter-1. Modified MS medium with BA (0.2 mg·liter-1) and NAA (0.01 mg·liter-1) was most effective in promoting shoot proliferation. Root initiation was achieved on half-strength modified MS medium with 2 mg IBA/liter. Rooted plants were hardened and established in the field. Chemical names used: N-(phenylmethyl)-1EZ-purin-6-amine (BA); 2-(1-naphthyl)acetic acid (NAA); 1H-indole-3-butyric acid (IBA).
Abstract
Germination was greater for seeds scarified manually or with 15% NaOCl than for those scarified with concentrated H2SO4. Fifteen percent NaOCl for 18 hr scarified the seed endocarp and negated the need for stratification. Germination of 85% was attained after 8 weeks incubation in the light at alternating 15°/30°C. This percentage compared favourably with 82% germination resulting from manual scarification techniques. Electron microscopy revealed that endocarp degradation was much more extensive after 18 hr in 15% NaOCl than after 4 days in a 1% solution.
Abstract
Embryo growth of the pecan (Carya illinoensis (Wang.) K. Koch) is mechanically restricted by the shell. This effect can rapidly be overcome by germinating the seeds between 30 and 35°C.
Abstract
Flower quality in Leucospermum can be improved by increasing the diameter and length of the reproductive shoot and by increasing floret initiation and capitulum size. During flower induction, endogenous cytokinin levels were low, with mainly “storage” forms of cytokinins being present. However, during flower differentiation, endogenous cytokinin levels increased and most of the activity was in the form of “free” cytokinins. One application of benzyladenine, if applied during the flower induction phase, increased both reproductive shoot diameter and the number of florets per capitulum.