MORPHO-ANATOMICAL FEATURES OF EARLY ONTOGENESIS OF EULOPHIA STREPTOPETALA (ORCHIDACEAE) IN VITRO
Alexandr A. Maksimov, Alexandr I. Shirokov, Vera V. Syrova, Alena E. Makarova
Lobachevsky Nizhny Novgorod State University, Nizhny Novgorod, Russia
Keywords: Orchidaceae, Eulophia, ontogenesis, protocorm, seedling, histological study, in vitro germination, root formation
Abstract
The morpho-anatomical features of germination of the tropical terrestrial orchid Eulophia streptopetala Lindl. were studied under conditions of asymbiotic in vitro cultivation. Seed germination was recorded 7 weeks after sowing. At the protocorm stage, early activity of the apical meristem, formation of rhizoids and appearance of stomata were observed, indicating early functional differentiation of the epidermis. A sequential development of the vascular system was established, progressing from isolated conductive elements to numerous scattered vascular bundles, along with the presence of idioblasts containing raphides. Under the experimental conditions, a tendency toward vegetative proliferation was observed, manifested by the formation of secondary protocorm-like structures. Formation of the first leaves and gradual reduction of the basal part of the seedling reflect the transition from heterotrophy to autotrophy. Endogenous root initiation was recorded at weeks 52-56 of cultivation; mature roots exhibited a multilayered velamen and a polyarch stele organization. The results confirm the high potential of E. streptopetala for mass propagation and ex situ conservation.
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