Antioxidantes, reguladores de crescimento e estresse térmico na embriogênese somática de Eucalyptus spp

• Autor(a) principal: Carvalho, Elisa Cristina Soares de
• Data de Publicação: 2007
• Tipo de documento: Tese
• Idioma: por
• Título da fonte: LOCUS Repositório Institucional da UFV
• Texto Completo: http://locus.ufv.br/handle/123456789/615
• topic: Reguladores de crescimento; Embriogênese somática; Estresse térmico; Growth regulators; Somatic embryogenesis; Thermal stress; CNPQ::CIENCIAS AGRARIAS::RECURSOS FLORESTAIS E ENGENHARIA FLORESTAL::SILVICULTURA

The objective of this work was to evaluate: a) effect of antioxidant substances on the control of oxidation in calli of juvenile explants from Eucalyptus grandis and E. urophylla; b) effect of TDZ on the induction of embryogenic calli in leaves and internodes of Eucalyptus grandis x E. urophylla clones; c) effect of temperature pre-treatment of explants on the induction of embryogenic calli in hybrid clones of Eucalyptus urophylla, and d) effect of TIBA, salicylic acid and acetyl salicylic acid on induction of embryogenic calli in cotyledons and hypocotyls of Eucalyptus urophylla. The parameters evaluated in the present work included percentage of callusing explants, callusing intensity, oxidation, color and texture of calli, and presence of embryogenic structures. In the experiments with the antioxidant substances, callus subculture onto fresh medium every 30 days and the different tested antioxidants were shown inefficient in stopping phenolic oxidation with subsequent explant death after a prolonged culture period. Significant differences were not found for callusing and texture in the different treatments, however, the addition of 10% of coconut water increased callusing of the explants and gave larger percentages of friable calli. In the experiments with TDZ, the combination of TDZ with dicamba and picloram produced calli of yellowish color, whereas the combinations with ZEA and NAA produced most calli of whitish color. The best callusing results were obtained with the treatments combining TDZ, ZEA and NAA. No root induction was observed in any of the treatments, and friable calli were produced only in one clone, but without any embryogenic structure. The use of TIBA, inhibitor of auxin transport, increased callusing intensity in calli induced by dicamba, picloram and 2,4-D. TIBA at the concentrations 0.75 and 1 mg L-1 changed texture from semifriable calli to friable calli, which showed at the end of 50 days a brilliant yellow color with little oxidation, but no embryogenic structures were observed. The pre-treatment at 4oC in combination with the growth regulators dicamba, picloram, TDZ and TDZ + IAA of two Eucalyptus clones did not result in satisfactory induction of somatic embryogenesis. However, with 1 mg L-1, there was formation of cell clusters differentiated into friable calli similar to pro-embryogenic structures in one clone, demonstrating that the cytokinin TDZ is promising for the development of a somatic embryogenesis protocol for adult Eucalyptus explants. The results of this work corroborate with the existing literature with respect to the difficulty in establishing an efficient protocol, with repeatability, for somatic embryogenesis in Eucalyptus species. Nevertheless, the importance of the technique and its applications in clonal silviculture emphasize the need for further studies that approach new possibilities in order to develop an efficient and reproducible somatic embryogenesis system for different species of the genus Eucalyptus.