Abstract
Tissue culture techniques have been employed for orchid mass propagation by means of the morphogenetic route of protocorm like-bodies (PLBs). This study aimed to analyze and compare Indole-acetic acid (IAA) and sugar endogenous levels in protocorm-like bodies (PLBs) induction and development in Cattleya tigrina, in order to better understand this process and to optimize micropropagation procedure protocols. Leaves grown on MS (Murashige and Skoog) culture medium, suplemented with 9 μM TDZ for PLBs induction and development were collected after 0, 2, 7, 14, 30, 60 and 100 days of cultivation, for further analysis. Increase of IAA and reduction of sugar levels are strongly related to morphogenetic response, that is, PLBs formation over the preexisting ones and leaf primordia formation. Sucrose, fructose and glucose presence in this study is related to cell signaling. Thus, hormonal signals and carbohydrates alter metabolism, triggering PLBs initiation and development in C. tigrina.
Highlights
The family Orchidaceae, with about 20,000 species distributed in 850 genera, is one of the largest and most specialized in the plant kingdom, found on almost all continents, especially in tropical and subtropical regions (Hossain et al, 2013)
Significant predominance of starch and protein material reserves was observed on the 30th day of cultivation, when, by histochemical analysis, the formation of large protocorm like-bodies (PLBs) amounts was verified, which resulted from new PLB formation over the preexisting ones (Figure 1M-O)
Leaf primordia formation began on the 60th day of cultivation, and the complete primordia formation was concluded on the 100th day of cultivation (Figure 1Q and T)
Summary
The family Orchidaceae, with about 20,000 species distributed in 850 genera, is one of the largest and most specialized in the plant kingdom, found on almost all continents, especially in tropical and subtropical regions (Hossain et al, 2013). Due to ornamental and landscape features, orchids are inordinately taken from their natural habitats, leading many species to extinction and significantly threatening biodiversity maintenance (Swarts & Dixon, 2009). Plant tissue culture technique has been widely used with success in the propagation of different land and epiphyte orchid species (Díaz & Álvarez, 2009), allowing rapid multiplication. Plant micropropagation can be used in the preservation and propagation of endangered species and as a model to study metabolism, differentiation and cell morphogenesis, providing information on physiological and biochemical events leading to in vitro morphogenesis modulation. A morphogenic response pattern defined as protocorm-like bodies (PLBs) has been proposed for several orchid species, such as the species under study
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