Influence of water regime on initial growth and essential oil of Eucalyptus globulus/Influencia do regime hidrico sobre o crescimento inicial e oleo essencial de Eucalyptus globulus

Understanding the water requirement of forest species in the seedling stage supports cost reduction by eliminating unnecessary irrigation in addition to providing higher productivity. This study was carried out to evaluate the effect of the water regime on initial growth, leaf production and content and chemical composition of the essential oil of Eucalyptus globulus, during the first 120 days of cultivation. The experiment employed a completely randomized design and was carried out at the Instituto de Ciencias Agrarias da Universidade Federal de Minas Gerais (ICA/UFMG), Montes Claros, MG. Treatments consisted of six different water regimes (50%, 75%, 100%, 125%, 150% and 175% of the reference evapotranspiration--ETo) with four replicates. Plant growth was evaluated by measuring linear dimensions--height, stem diameter and number of leaves. The essential oil was extractedfrom fresh leaves by hydrodistillation in a Clevenger apparatus. The present study demonstrated that irrigation depths corresponding to 75% of the ETo are responsible for increased growth of E. globulus and increased dry matter production of leaves. The lowest irrigation levels were responsible for the greatest essential oil content. The essential oil was analyzed by gas chromatography-mass spectrometry (CG-MS), and eucalyptol (40.84% to 55.72%) was reported to be the major compound for all treatments. Compounds such as [beta]-myrcene, [alpha]-Gurgujeno, Alloromadendreno, Varidiflorene appear under specific irrigation conditions. Key words: Eucalyptus, Irrigation, Water stress, Eucalyptus globulus. Conhecer a exigencia hidrica de especies florestais na fase de muda, alem de proporcionar maior produtividade, possibilita reduzir custos, eliminando irrigacoes desnecessarias. Este estudo foi realizado com o objetivo de avaliar o efeito dos regimes hidricos no crescimento inicial, producao de folhas, teor e composicao quimica do oleo essencial de Eucalyptus globulus, nos primeiros 120 dias de cultivo. O trabalho foi conduzido no Instituto de Ciencias Agrarias da Universidade Federal de Minas Gerais (ICA/UFMG), Montes Claros, MG, empregando o delineamento inteiramente casualizado. Os tratamentos consistiram em seis regimes hidricos (50%, 75%, 100%, 125%, 150% e 175% da Evapotranspiracao de referencia--ETo), com quatro repeticoes. O crescimento das plantas foi avaliado por meio de dimensoes lineares--altura, diametro do coleto e numero de folhas. O oleo essencial foi extraido das folhas frescas e