Light quality and natural ventilation have different effects on protocorm development and plantlet growth stages of the in vitro propagation of Epidendrum fulgens (Orchidaceae)

Abstract

Improvements of in vitro culture protocols are essential to increase productivity in order to ensure their practical application in commercial laboratories. The aim of the present work was to evaluate the influence of light sources of different wavelengths in combination with natural ventilation of the in vitro atmosphere (NV) in all steps of the micropropagation, from the seed germination and protocorm development (SGS) to plantlet growth (PGS), as well as for ex vitro acclimatization. Additionally, we compared the use of a temporary immersion bioreactor (Plantform™) and NV for the PGS. We evaluated the parameter effects on the velocity of development of protocorms, and the productivity and quality of plantlets, accessing both morphological and biochemical features, as velamen formation, stomatal functionality, photosynthetic pigments and microscopic features. For SGS, NV was detrimental. W and DR. LED lights accelerated protocorm development, while fluorescent light increased their fresh weight. For PGS, NV was responsible not only to enhance fresh weight and root number, but also stimulated the development of velamen and the functionality of stomata. NV also increased photosynthetic pigment concentration and sclerenchyma formation in leaves. Plantform™ increased the fresh weight, the number of organs, and leaves had thicker cuticles.