Pre and post-severance effects of light quality on carbohydrate dynamics and microcutting adventitious rooting of two Eu

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ORIGINAL PAPER

Pre and post-severance effects of light quality on carbohydrate dynamics and microcutting adventitious rooting of two Eucalyptus species of contrasting recalcitrance Carolina Michels Ruedell • Ma´rcia Rodrigues de Almeida Jose´li Schwambach • Carina Fronza Posenato • Arthur Germano Fett-Neto



Received: 14 October 2011 / Accepted: 8 October 2012 / Published online: 20 October 2012 Ó Springer Science+Business Media Dordrecht 2012

Abstract Adventitious rooting is a complex developmental response affected by genetic and environmental factors. Radiation quality effects on adventitious rooting depend on characteristics such as species, growth stage, irradiance, spectral quality, and time of exposure. Eucalyptus is an essential genus for the paper industry, and high yield plantations depend on adventitious rooting of selected genotypes. This work addressed two hypotheses: (1) radiation quality equally affects adventitious rooting in Eucalyptus species of different recalcitrance; (2) adventitious rooting outcome depends on both donor plant and cutting radiation quality treatments. To that end, the easy-to-root Eucalyptus grandis and the recalcitrant Eucalyptus globulus were evaluated. The effect of white, blue, red and far-red radiation enrichment on microcuttings and donor plants of both species was evaluated in relation to rooting. There was no effect of radiation quality on adventitious rooting of E. grandis or when radiation treatments were applied to E. globulus microcuttings. In contrast, donor plants of E. globulus, grown in medium C. M. Ruedell  M. R. de Almeida  C. F. Posenato  A. G. Fett-Neto (&) Graduate Program in Cell and Molecular Biology, Center for Biotechnology, Federal University of Rio Grande do Sul (UFRGS), C.P.15005, Porto Alegre, RS CEP 91501-970, Brazil e-mail: [email protected] C. M. Ruedell  M. R. de Almeida  C. F. Posenato  A. G. Fett-Neto Department of Botany, Graduate Program in Botany, Plant Physiology Laboratory, UFRGS, Avenida Bento Gonc¸alves, 9500, pre´dio 43423–Bloco 4, Porto Alegre, RS CEP 91509-900, Brazil J. Schwambach Graduate Program in Biotechnology, Institute of Biotechnology, University of Caxias do Sul, Bloco 57, rua Francisco Getu´lio Vargas 1130, Caxias do Sul, RS CEP 95070-560, Brazil

devoid of sucrose and exposed to far-red radiation, yielded microcuttings showing higher rooting percentage, even in the absence of exogenous auxin in the rooting medium. Sucrose in donor plant medium abolished the positive effect of far-red radiation. An increase in endogenous soluble sugars and starch contents in basal microcuttings was associated with far-red radiation treatment of donor plants. These results underline the importance of appropriate carbohydrate partitioning in donor plants for adventitious rooting of cuttings and provide a basis for understanding and overcoming rooting recalcitrance in E. globulus clones. Keywords Adventitious rooting  Carbohydrates  Donor plant  Eucalyptus  Radiation quality

Introduction Eucalyptus is one of the most widely