Post-seminal development and morphophysiological responses to light spectral quality during in vitro culture of Cattleya purpurata (Lindl. & Paxton) Van den Berg

Abstract

Cattleya purpurata is an orchid species endemic to the Brazilian Atlantic Forest with high ornamental and ecological value. This study characterized its post-seminal development from seed germination to plantlet formation and evaluated the effects of different light spectra on growth, photosynthetic pigments, and subsequent ex vitro acclimatization. Mature seeds were asymbiotically germinated on Murashige and Skoog medium under white, blue, red, and blue/red LED light. Morphological and anatomical development was monitored throughout culture, and growth and pigment accumulation were evaluated. Embryo swelling occurred after seven days, testa rupture at 28 days, and the differentiation of true leaves and adventitious roots between 90 and 128 days. Anatomical analyses revealed early establishment of bipolar organization and differentiation of the shoot and root apical meristems. Light quality significantly affected plantlet development and pigment accumulation: white light promoted higher chlorophyll b and carotenoid contents, whereas blue-containing spectra, particularly blue/red, enhanced biomass accumulation, root formation, and plantlet production. During ex vitro acclimatization, the light spectrum applied during in vitro culture affected fresh mass accumulation, with higher values in plantlets previously exposed to blue and blue/red light, but did not affect survival or new shoot production. Overall, spectral quality influenced both developmental and physiological responses of C. purpurata, and blue-containing spectra showed potential for improving plantlet growth and post-transplant performance. Post-seminal development of Cattleya purpurata was successfully characterized in vitro, revealing key ontogenetic and anatomical events from germination to seedling formation. Blue/red LED light significantly improved seedling growth and establishment, supporting its use in propagation and conservation strategies.