Aspectos morfofisiológicos e anatômicos de plântulas de Handroanthus impetiginosus: reguladores de crescimento, trocas gasosas e enriquecimento de CO2 no cultivo in vitro

Abstract

Handroanthus impetiginosus, popularly known as ipê roxo (purple trumpet tree), is a woody species with significant pharmacological, timber, and ornamental potential; however, it faces propagation limitations. In vitro cultivation techniques—such as germination, multiplication, rooting, and CO2 enrichment—offer excellent alternatives for propagating this species. Thus, this study aimed to establish, multiply, and root the species in vitro, as well as to analyze the impact of sucrose and CO2 enrichment on the development and anatomy of ipê roxo. Chapter I presents the theoretical background, addressing key topics regarding the species' in vitro cultivation. Chapter II details the in vitro seed germination, multiplication (using stem segments), and rooting (using shoots) of ipê roxo. Seeds were surface-sterilized and inoculated onto ½ MS culture medium without growth regulators. WPM medium supplemented with the cytokinins m-TP and BAP (0, 2.5, and 5 μM) was used for stem segment multiplication, while WPM medium with the auxins NAA and IBA (0, 3, and 6 μM) was used for rooting. After 45 days of cultivation, 5 μM m-TP emerged as the superior cytokinin for ipê roxo multiplication, and IBA at moderate concentrations proved effective as a root inducer in micropropagation protocols. In Chapter III, stem segments derived from the multiplication phase—inoculated onto WPM medium supplemented with sucrose (0, 10, and 20 g L⁻¹) and 5 μM m-TP—were placed in two climate chambers: one with ambient CO2 concentration (420 ± 30 μmol mol⁻¹) and the other with elevated CO2 concentration (800 ± 30 μmol mol⁻¹). After 35 days of culture, it was observed that 10 g L⁻¹ sucrose + 800 μmol mol⁻¹ CO₂ maximized growth and photosynthetic efficiency during the in vitro culture of ipê roxo (purple trumpet tree), particularly during the transition phases to autotrophy, while 20 g L⁻¹ sucrose + 800 μmol mol⁻¹ CO₂ influenced the species' anatomy. This study presented interesting results that enable the establishment of a protocol for the multiplication and rooting of ipê roxo, which can serve as a basis for large-scale plant propagation. The findings also indicate the possibility that H. impetiginosus exhibits a degree of physiological and anatomical plasticity in response to high CO₂ concentrations—such as those predicted in climate change scenarios—suggesting the species possesses adaptive potential.