Diodos emissores de luz no crescimento in vitro de Oncidium varicosum

Abstract

Oncidium varicosum is an epiphytic orchid native and endemic to Brazil, with tissue culture being an important technique for its cultivation. Light quality is one of the factors that directly affects plant growth in vitro and can be adjusted according to the light-emitting diodes (LEDs) used. However, plant responses to these lights and combinations between them vary according to the species. Thus, the objective was to analyze the influence of light-emitting diodes (LEDs) on the in vitro growth of Oncidium varicosum var. rogersii, aiming for the flourishing of the species. For this, the phytotechnical, anatomical and physiological characteristics of the plants were evaluated after 90 days of cultivation under white, red, blue and purple (2R:1B) LEDs. Greater fresh mass production was obtained in plants grown under purple LED, while red LED provided greater length of shoots and shoots. Increased levels of chlorophyll a, b and total and carotenoids were also observed in purple LED. Regarding anatomy, plants grown under purple LED showed greater thickness of cuticle, epidermis, mesophyll and leaf and greater ostiole area. Plants grown under red LED showed greater stomatal density and blue LED allowed greater stomatal functionality in plants. It is concluded that the purple LED is the most suitable for the in vitro cultivation of O. varicosum var. rogersii, as it promotes greater production of fresh mass, increased levels of photosynthetic pigments and greater thickness of cuticle, epidermis, mesophyll and leaf.