Seedling response of three Eucalyptus species to copper and zinc toxic concentrations

Human activities have continuously increased the level of heavy metal ions circulating in the environment. It is important to understand the tolerance of plant species to high concentrations of heavy metals. Very little is known on the response of Eucalyptus species to Zn and Cu toxic concentrations Eucalyptus camaldulensis, E. microtheca, and E. occidentalis seeds were grown in silt and irrigated by nutrient solution. Forty two days old seedlings were exposed to ten Zn and Cu treatments for ten months. The tolerance order of the species to toxic concentrations of Cu was Eucalyptus camaldulensis> E. occidentalis> E. microtheca and the tolerance order of the species to toxic concentrations of Zn was E. occidentalis> E. microtheca> E. camaldulensis. Tissue concentration increased as Zn and Cu concentration increased for the species. Root tissue concentrations regards to Zn and Cu concentrations were higher than shoot tissue concentration at all solution. These results provided the first quantified metals in Eucalyptus species and the second explored relationships between concentrations of metals in nutrient solution and plant organs

Macropropagation and micropropagation of Ziziphus spina-christi Macropropagação e micropropagação de Ziziphus spina-christi

Christ's thorn (Ziziphus spina-christi (L.) Desf.) is a cross-pollinated plant with a wide range of genetic variability in nature and, for this reason, vegetative propagation assumes importance for improvement programs. The objective of this work was to evaluate cutting, T budding and tissue culture methods for this species. Shoots of 22-25 cm length were treated by two culture media and three shoot diameters for cutting trial. The T budding treatments consisted of three and five collection dates in spring and autumn, respectively. Tissue culture nodal segments bearing axillary buds were removed from shoots of mature trees at different seasons. Experiments to determine the best disinfectant chemical, appropriate conditions and materials to prevent phenolic compound exudation, explant characteristics, media type and cytokinin-auxin ratios were carried out. Successful rooting happened only on the sand beds and with cuttings greater than 8 mm diameter. The effects of T budding seasons on budtake percentage were significantly different. The best time for explant harvesting was mid of summer. Amount of rooting on media containing IBA as well as activated charcoal and disinfection with Ca(OCl)2 at concentration of 5% for 20 minutes were the best treatments.<br>Ziziphus spina-christi (L.) Desf. é uma planta de polinização cruzada com grande variabilidade genética na natureza e, por isso, sua propagação vegetativa assume importância para o melhoramento genético. O objetivo deste trabalho foi avaliar os métodos de estaquia, borbulhia em T e cultura de tecido na propagação vegetativa desta espécie. No ensaio de estaquia, partes aéreas da planta com 22-25 cm foram cultivadas em dois meios de cultura e com três diâmetros. O ensaio de borbulhia consistiu na coleta do material em três datas na primavera e em cinco datas no outono. Os segmentos nodais contendo gemas axilares foram removidos da parte aérea de árvores maduras, em diferentes estações do ano, e avaliados em relação à esterilização química, exudação de compostos fenólicos e cultivo. O enraizamento ocorreu apenas em camas de areia e em estacas maiores do que 8 mm. Houve efeito significativo da estação do ano sobre a porcentagem de brotação. O melhor período para coleta do explante foi no verão. O meio contendo IBA e carvão ativado apresentou maior quantidade de raízes e o melhor desinfestante foi Ca(OCl)2 na concentração de 5%, por 20 minutos