Factors affecting adventitious root formation in isolated stem segments of Rhododendron.

Stem expiants of the rhododendron cultivar Catawbiense Album rooted more easily in vitro than those of Pink Pearl, agreeing with the experience of nursery practice. Rooting occurred only on segments of young soft shoots and was strongly promoted when the expiants were placed inverted on the medium. Continuous light inhibited, whereas continuous darkness promoted rooting. Rooting occurred only in the presence of an auxin together with a sugar in the culture medium. There was no evidence that mineral nutrition and temperatures between 21 degrees and 29 degrees C. play an important role.-Univ. Wageningen. (Abstract retrieved from CAB Abstracts by CABI’s permission

Relative dormancy in excised vegetative buds of Rhododendron.

Excised vegetative buds of Rhododendron cv. Pink Pearl, present in the axils of the bud scales, required light for sprouting, but no special daylength was necessary to break dormancy. Glucose greatly enhanced sprouting, but was not essential. Glucose could not replace light, but light could partly replace glucose for inciting sprouting. Only fully developed buds were capable of sprouting. Temperature played a decisive role, 21-25 deg C being the optimum range. Macroelements were not essential, but sprouting on a medium without macroelements was reduced. It was impossible to induce adventitious root formation on excised shoots grown on a medium containing IBA. (Abstract retrieved from CAB Abstracts by CABI’s permission

Callus multiplication of Anthurium andraeanum Lind. in liquid media.

The growth of callus tissue from adult A. andraeanum plants was best in a modification of Murashige and Skoog's medium. On this medium genotype A 42-3 reached a fresh weight multiplication rate of 30.7 when grown for 5 weeks at a rotation speed of 120 rev/min, at 25 deg C and in continuous darkness. The fresh weight multiplication rate of 6 other genotypes of the same species varied considerably when grown on the best medium for A 42-3. (Abstract retrieved from CAB Abstracts by CABI’s permission

Freesia plantlets from flower-buds cultivated in vitro.

Flower-buds of 10 freesia cvs were grown in vitro and were induced to regenerate adventitious buds on a modified Murashige and Skoog's medium containing PBA and IAA. The formation of adventitious buds was strongly enhanced by growing the explants first in darkness and subsequently in light. Subcultured shoots, grown on a medium with IAA, could be rooted easily and viable plants were obtained. (Abstract retrieved from CAB Abstracts by CABI’s permission

Regeneration of bulblets on bulb scale segments of hyacinth in vitro.

Hyacinth bulbs, cv. Pink Pearl, harvested in June were held at 25 deg C for 1-5 months, after which bulb scales were removed for tissue culture in modified basic medium. The length of the holding period had little effect on the number of bulblets that regenerated, but the average bulb weight increased as the holding period lengthened, attaining a maximum with bulbs held until 1-15 October. There were wide differences in regenerative ability and bulblet growth between bulbs of the same harvest and size. The number of bulblets that regenerated was not affected by scale age, but bulblet growth from the older scales (nos. 7-18) was much better than from the younger scales. Regeneration and growth of explants from the proximal parts of the scales was much better than from the distal parts, and 3-cm-long explants gave much better results than shorter ones. Inverting the explants in the culture medium was favourable to regeneration and growth. In further studies on the effects of temperature and light, bulb regeneration was accelerated by raising the temperature, the optimum being 21.6 deg . The greatest number of bulblets/explant, however, was obtained at 13 deg , and the highest bulb weight at 21.6 or 24.8 deg . There were no differences in regeneration and bulblet growth between scales grown in continuous light or in darkness. (Abstract retrieved from CAB Abstracts by CABI’s permission

Vegetative propagation of Freesia through the isolation of shoots in vitro.

Shoots from the cvs Ballerina, Aurora, Rijnveld's Golden Yellow and Rose Marie, originating from excised flower-buds, were grown in vitro and were induced to form shoots on a modified Murashige and Skoog medium containing PBA and IAA. The greatest number of new shoots/excised shoot was obtained when the medium contained PBA at 5 mg/l and IAA at 0.1 mg/l. The number of shoots formed depended on the cv. tested. Subcultured shoots, grown on a medium with IAA but without PBA, could be rooted easily and viable plants were obtained. (Abstract retrieved from CAB Abstracts by CABI’s permission

Vegetative propagation of freesia through callus cultures.

Isolated segments of corm, stem, leaf, flower bud and anther from flowering freesia plants, cv. Ballerina, were induced to form callus on a modified Murashige and Skoog medium supplemented with NAA and 6-(benzylamino)-9-(2-tetrahydropyranyl)-9H-purine (PBA). Callus induction was best with young flower buds kept at 25 deg C in darkness. Callus could be sub-cultured in darkness on a medium containing auxin and cytokinin. Complete plantlets were obtained either by transferring the callus to light on an auxin-free medium containing kinetin or PBA, or from young anthers. Adventitious organ formation in explants and callus was closely related to the auxin/cytokinin ratio in the medium, rooting being promoted by auxins and bud formation by cytokinins. Root and bud formation were greater in light than in darkness. (Abstract retrieved from CAB Abstracts by CABI’s permission