ABSTRACT In 2019, the atmospheric CO2 concentration exceeded the 415 ppm milestone for the first time in the human history. According to projections of the Intergovernmental Panel on Climate Change (IPCC), CO2 levels will continue to rise in the future, potentially affecting all living organisms. Plants with C3 metabolism may benefit from rising CO2 levels because the significant losses of photosynthesis, driven by photorespiration could be diminished under this scenario. This study addressed the anatomical changes in the stems of young Eucalyptus urophylla plants induced through cultivation in elevated CO2 (eCO2). Plants cultivated under eCO2 showed increased stem diameter (i.e., radial width of the secondary xylem, secondary phloem and cortex tissues). Periodic acid-Schiff (PAS)/Toluidine Blue staining suggested a decrease in the lignification content in the newly formed tissues of eCO2 stimulated plants. Levels of caffeate/5-hydroxyferulate O-methyltransferase form 1 (COMT1), a lignin biosynthesis specific proteoform, were significantly reduced in stem sections, supporting our findings: eCO2 induces plant growth, but reduces lignified tissues.

Eucalyptus urograndis is a hybrid eucalyptus of major economic importance to the Brazilian pulp and paper industry. Although widely used in forest nurseries around the country, little is known about the biochemical changes imposed by environmental stress in this species. In this study, we evaluated the changes in the stem proteome after short-term stimulation by exposure to low temperature. Using two-dimensional gel electrophoresis coupled to high-resolution mass spectrometry-based protein identification, 12 proteins were found to be differentially regulated and successfully identified after stringent database searches against a protein database from a closely related species (Eucalyptus grandis). The identification of these proteins indicated that the E. urograndis stem proteome responded quickly to low temperature, mostly by down-regulating specific proteins involved in energy metabolism, protein synthesis and signaling. The results of this study represent the first step in understanding the molecular and biochemical responses of E. urograndis to thermal stress.

Piper solmsianum é uma espécie herbácea do sudeste brasileiro onde vários compostos biologicamente ativos já foram identificados. O objetivo deste trabalho foi estabelecer suspensões celulares nesta espécie. Para tanto, foram utilizados explantes de pecíolos e folhas, retirados de plântulas cultivadas in vitro, os quais foram submetidos a diferentes combinações de reguladores de crescimento (AIA, ANA, 2,4-D e BAP). Foi obtida a neo-formação de raízes e brotos, estes últimos através do processo de organogênese indireta evidenciada por estudos histológicos. Para a indução e crescimento dos calos, foram avaliados, além das diferentes combinações de reguladores de crescimento, a suplementação ao meio de cultura de carvão ativado (1,5 mg.l-1) e o regime de luz. Culturas mantidas na luz, em meio de cultura suplementado com 0,2 mg.l-1 2,4-D e 2 mg.l-1 BAP e sem carvão ativado, resultaram em maior crescimento (massa fresca) dos calos. A partir destes calos, foram obtidas suspensões celulares, cuja dinâmica de crescimento e acúmulo de metabólitos foi estudado. Os resultados obtidos deverão ser utilizados para a caracterização de rotas biosintéticas em culturas in vitro em P. solmsianum.

Piper solmsianum is a shrub from Southeast Brazil in which many biologically active compounds were identified. The aim of this work was to establish a cell suspension culture system for this species. With this in mind, petiole and leaf explants obtained from in vitro plantlets were cultured in the presence of different plant growth regulator combinations (IAA, NAA, 2,4-D and BA). Root and indirect shoot adventitious formation, detected by histological analysis, was observed. Besides the different combinations of plant growth regulators, light regime and the supplement of activated charcoal (1.5 mg.l-1) were tested for callus induction and growth. Cultures maintained in light, on a 0.2 mg.l-1 2,4-D and 2 mg.l-1 BA supplemented medium, and in the absence of activated charcoal, showed the highest calli fresh matter increment. From a callus culture, cell suspension cultures were established and their growth and metabolite accumulation studied. The achieved results may be useful for further characterization of the activated secondary metabolites pathways in in vitro systems of P. solmsianum.