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Six broadleaved tree species and Picea abies (L.) Karst. were planted under spruce plantations of varying densities, in Sweden. Treatments included control (994 stems ha-1), dense (538 stems ha-1), sparse (294 stems ha-1) and gap (0 stems ha-1) overstory treatments. There was an increase in height and diameter growth from control to sparse overstory treatment of all underplanted tree species except for ash (Fraxinus excelsior L.) and Norway maple (Acer platanoides L.). Site conditions may have hampered the growth of these species, as well as wild cherry (Prunus avium L.). Both oak (Quercus robur L.) and spruce had greater growth in the gap treatment, relative to the other treatments. Insecticide application did not influence seedling growth or survival. The performance of beech (Fagus sylvatica L.), lime (Tilia cordata Mill.), spruce and oak was consistent with shade tolerance ranking. Beech and lime had a very high survival rate, even under the densest canopy. The growth and mortality of ash, maple and wild cherry differed significantly from what was expected. This experiment demonstrated significant variation in interspecific growth and mortality between seven planted tree species in relation to canopy density. Correct site and species selection is crucial when underplanting in shelterwood systems. [ABSTRACT FROM AUTHOR]

In vitro root formation was studied in petiole explants from Pelargonium × hortorum Bailey cv. Radio exposed to different irradiance (2.5. 11.6 or 23.0 W/m²). Optimal root formation was found when stock plants were subjected to 2.5 W/mm² and explants were grown on a medium with 20 g/1 of sucrose and 5.0 mM of nitrogen. The number of roots per explant decreased with increasing nitrogen or sucrose concentrations in the growth medium and with increasing irradiance applied to the stock plants. Variation in temperature (17, 21 or 25°C) did not affect root formation. The number of roots per explant was higher in explants from young petioles than in explants from older petioles. The initial nitrogen content of the explants was highest at the lowest irradiance. The content of reducing sugars and sucrose increased with increasing irradiance. The endogenous levels of lysine. arginine and ornithine were highest at 2.5 W/mm² and the levels of proline. alanine, γ-aminobutyric acid, glutamic acid, glutamine. aspartic acid and asparagine were highest at 23.0 W/mm². With rising nitrogen concentration in the medium, the final endogenous content of nitrogen in the explants increased, whereas the content of reducing sugars decreased. When the sucrose concentration in the medium increased, the endogenous content of reducing sugars rose, and the nitrogen level was lowered. Variations in the nitrogen concentration in the growth medium influenced the final level of free amino acids in the explants. [ABSTRACT FROM AUTHOR]

Petiole explants from 17 cultivars of Begonia × hiemalis were grown on a basal agar medium with different combinations of NAA and BA as well as on media lacking microelements or vitamins. The stock plants were kept either under short days (7-8 h of light per day) at 15°C or under long days (15-16 h of light) at 18-21°C. The day length during the in vitro culture was 20 h of light and the temperature 2 1°C. Explants from short-day treated stock plants did not show any differentiation. In explants from long-day treated stock plants, the percentage of explants with shoot, root and with both shoot and root initiation were recorded after 55 days. Explants forming both shoots and roots were transferred to soil, and plantlet formation was observed after another 55 days. The percentage of explants with organ and plantlet formation differed between cultivars. With increasing NAA and decreasing BA concentrations, the percentage of explants forming only roots increased, whereas the percentage of explants with only shoots decreased. Plantlet formation was most frequent in explants from NAA : BA ratios of 2: 1 and 10: 1, and a variation was found between different cultivars. When the vitamin fraction was not added to the medium, this did not influence formation of shoots, roots and plantlets. When the microelements were omitted, shoots, roots and callus were formed, but no plantlets. [ABSTRACT FROM AUTHOR]

Hypocotyl explants of Beta rulgaris L. were grown on defined agar media with different combinations of IAA and kinetin at varying concentrations of nitrogen or sucrose. The cultures were kept in light (18 h a day) at 27°C for 5 weeks. Root initiation and callus growth were recorded and the callus tissue was analysed for N and K. Root formation was found to increase with increasing nitrogen concentration (from 5 mM to 23.3 mM) in the medium at 10.0 mg/I of IAA, whereas no stimulation was found at 0.1 mg/l of IAA. When raising the sucrose level from 20 g/l to 100 g/l at 10.0mg/I of IAA and 1.0mg/I of kinetin. root initiation was also stimulated. At a lower kinetin and auxin level, however, no increase was recorded. Callus growth was affected by changes in the nitrogen or sucrose concentration of the culture media. The nitrogen content of the callus tissue increased with rising nitrogen concentration of the media. When raising the sucrose level instead of the nitrogen level, the nitrogen content of the tissue decreased. [ABSTRACT FROM AUTHOR]