Light has direct influence on growth and development by altering the morphophysiology of the plant and the content and composition of secondary metabolites. The present study aimed to evaluate the yield and composition of the essential oil of Tetradenia riparia cultivated under different shading levels. Plants were propagated by cuttings and cultivated either under full sunlight and in environment completely covered by black polyethylene sheeting to obtain shading levels of 30%, 50%, and 80%. Plants were grown under experimental conditions for 150 days. The essential oil was extracted from fresh leaves in triplicate for each treatment through steam distillation with a modified Clevenger apparatus. The components of the essential oil were identified using a gas chromatograph coupled with a mass spectrometer (GC/MS), and compared to retention indices and authentic mass. The largest yields of essential oil came from plants cultivated under 30% and 50% shading, followed by plants cultiveted under full sunlight and under 80% shading. The main component found was the sesquiterpene hydrocarbon 14-hydroxy-9-epi-(E)-caryophyllene. Some components, such as verbenone, were only found in the treatment under full sunlight, while numerous others were exclusive to the different shading treatments. The yield and chemical composition of the essential oil of T. riparia is influenced by the level of shading.

RESUMO-Com o objetivo de estudar o papel da luz sobre o desenvolvimento de Tetradenia riparia avaliaram-se características morfofisiológicas quando cultivada sob 30%, 50% e 80% de sombreamento e a pleno sol. A espessura do limbo foliar foi maior em plantas cultivadas a pleno sol. A área foliar foi maior em plantas cultivadas a 80% de sombreamento. Teores de clorofila "a" e total, carotenoides, proteínas e nitrogênio foram maiores nas plantas cultivadas a 50% e 80% de sombreamento. Não ocorreram diferenças para densidade estomática e tricomas na epiderme abaxial, nos teores de clorofila "b" e razão clorofila a/b e valores de cinzas entre plantas cultivadas nos diferentes tratamentos. A densidade estomática foi maior na epiderme adaxial de plantas cultivadas a 30% de sombreamento. O teor de lipídios foi menor nas plantas crescidas a 80% de sombreamento. T. riparia tem alta plasticidade morfofisiológica a ambientes com diferentes intensidades de radiação.

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