Anatomical and ultrastructural studies reveal temporal and spatial variation in the oil production in leaves of the dies
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ORIGINAL ARTICLE
Anatomical and ultrastructural studies reveal temporal and spatial variation in the oil production in leaves of the diesel tree (Copaifera langsdorffii, Leguminosae) Plácido Fabrício Silva Melo Buarque 1,2 & Silvia Rodrigues Machado 3 & Tatiane Maria Rodrigues 3 Received: 25 November 2019 / Accepted: 4 June 2020 # Springer-Verlag GmbH Austria, part of Springer Nature 2020
Abstract The oily resin produced by Copaifera langsdorffii, commonly called oil of copaiba, is widely exploited by the drug, cosmetic, and biodiesel industries. The distribution of oily secretory cavities and canals (secretory spaces) over the vegetative body characterizes this species. Oil is stored inside the lumen of the secretory spaces and only reaches the organ surface after injuries. Nonetheless, translucent oily deposits occur on the adaxial surface of intact young leaves. In this study, we searched for further sources of oil production in C. langsdorffii leaves in addition to the well-known secretory cavities and investigated the mechanisms of secretion. Leaves in different developmental stages were collected from adult plants and processed for studies on light and transmission electron microscopies. The primary finding of this study was the involvement of the chlorenchyma cells in lipid biosynthesis, in addition to the secretory cavities. The secretory activity of cavities and chlorenchyma cells overlapped in young leaves. Ultrastructurally, secretory cavity cells exhibited abundant smooth endoplasmic reticulum profiles and oleoplasts, whereas the chlorenchyma cells had large chloroplasts with oil inclusions. Our data suggest that the oily material on the leaf surface arose from the chlorenchyma and was transported via the apoplast. These findings open new avenues for understanding oil biosynthesis regulation in mesophyll cells and planning of future strategies for the biotechnological application of C. langsdorffii leaves. Keywords Cell ultrastructure . Copaiba . Leaflet . Oil biosynthesis . Secretory cavity . Secretory chlorenchyma
Introduction In South America, some Leguminosae species, mainly those belonging to the genera Copaifera and Hymenaea, are known for their massive production of terpenoid oily resins which are of economical, ecological, and medicinal importance (Langenheim 2003). In plants of both genera, such substances
Handling Editor: Dorota Kwiatkowska * Tatiane Maria Rodrigues [email protected] 1
Graduate Program in Biological Sciences (Botany), Institute of Biosciences, São Paulo State University (UNESP), Botucatu City, São Paulo State, Brazil
2
Goiás State University (UEG), Iporá City, Goiás State 76200–000, Brazil
3
Department of Botany, Institute of Biosciences, São Paulo State University (UNESP), Botucatu City, São Paulo State 18618–970, Brazil
are produced in internal glands called secretory canals and cavities (Milani et al. 2012; Paiva and Machado 2007). In these glands, the oily secretion produced by epithelial cells is stored in a wide intercellular space (lumen) until some i
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