Aspectos fisiológicos de Cedrela fissilis Vellozo germinada in vitro sob condições de ventilação natural

Abstract

Deforestation and rising atmospheric CO₂ levels threaten valuable tree species such as Cedrela fissilis. In this context, in vitro culture associated with natural ventilation in photoautotrophic and photomixotrophic systems represents a promising alternative for its conservation. Therefore, it is relevant to investigate how different in vitro cultivation strategies may affect the performance of this species under controlled conditions. This study aimed to evaluate the effects of photoautotrophic and photomixotrophic systems with natural ventilation on the development and physiological and anatomical characteristics of C. fissilis plants germinated in vitro. Seeds were disinfected and inoculated under different growing conditions, and two experiments were conducted: (E-I) a 2 × 2 × 2 factorial design evaluating sucrose concentrations (0 or 20 g L⁻¹), agar (0 or 5.5 g L⁻¹), and porous membranes (absence or presence). Germination parameters (% germination, % seedling formation, mean germination time—MGT, and mean seedling formation time—MSFT), growth traits (hypocotyl, shoot and primary root length; number of leaves, nodes, and roots), photosynthetic pigment contents, and anatomical traits (micromorphometry) were assessed. (E-II) a 2 × 2 factorial design evaluating the number of porous membranes (2 or 4) and CO₂ concentration ([CO₂], 420 or 800 ppm). The same growth and physiological analyses as in E-I were performed, with the addition of relative water content (RWC). In E-I, the presence of porous membranes enhanced seedling development in both culture media, particularly in the semisolid medium, which produced plants with superior growth and intense leaf greening even without sucrose supplementation. Sucrose supplementation (20 g L⁻¹) promoted improved plant development, especially when combined with membranes, resulting in greater fresh and dry biomass of shoots and roots, increased hypocotyl and shoot length, higher numbers of nodes and roots, and greater leaf area. Additionally, the membrane significantly increased chlorophyll b and carotenoid concentrations in C. fissilis plants. In E-II, increasing [CO₂] to 800 ppm and higher membrane permeability (four membranes) promoted greater shoot growth, higher dry biomass, larger leaf area, and increased numbers of lateral roots. Maximum root length and stem diameter were not affected, whereas root diameter varied depending on the interaction between CO₂ and permeability. Photochemical parameters (Fv/Fm, Fv/F₀, RC/ABS, and PI) remained stable, indicating preserved photosystem II functionality. Chlorophyll a and total chlorophyll contents increased with higher [CO₂] and permeability, whereas chlorophyll b remained unchanged. Carotenoids showed variable responses, with reductions under high permeability and elevated CO₂. Overall, combining porous membranes with semisolid medium, sucrose supplementation, elevated [CO₂] (800 ppm), and higher membrane permeability enhanced growth, biomass accumulation, and physiological performance of C. fissilis in vitro without impairing photochemical function. These strategies optimize the cultivation environment and support the micropropagation and acclimatization of the species.