CO2 enrichment leads to altered cell wall composition in plants of Pfaffia glomerata (Spreng.) Pedersen (Amaranthaceae)

Abstract

Pfaffia glomerata, popularly known as Brazilian-ginseng, stands out as a species of medicinal interest that has a high photoautotrophic potential for in vitro cultivation. This study aimed to analyze cell wall components of P. glomerata during in vitro cultivation in a CO2-enriched atmosphere. For this, P. glomerata plants were grown in MS medium without sucrose, in acrylic chambers with continuous forced air ventilation at 400 and 1000 μL L−1 CO2, and a control treatment with flasks put outside the chambers, without forced ventilation. The experiment was evaluated at 20, 30 and 40\xa0days of cultivation, totaling nine treatments in a 3\u2009×\u20093 factorial scheme (CO2 concentration × days), with 4 replications. Analyses of growth, photosynthesis and cell wall immunohistochemistry (using monoclonal antibodies JIM7, JIM13 and LM10) were done. The CO2 enrichment at the concentration of 1000 μL L−1 induced greater growth and accumulation of dry mass, in addition to increasing the photosynthetic rate. Immunohistochemistry analyses showed that the presence of homogalacturonan pectins detected by the JIM7 antibody decreased from 20 to 40\xa0days, regardless of CO2 treatment. The deposition of heteroxylan and the JIM13 AGP epitope was detected exclusively in the secondary wall regions, with higher intensity in the treatment of 1000 µL L−1 CO2. This work opens new perspectives to understanding the dynamics between photoautotrophy and cell wall deposition in P. glomerata. P. glomerata under elevated CO2 produces more pectic polysaccharides and hemicelluloses in the cell wall; increasing pectic polymers and xylans are associated with dry biomass gain in P. glomerata under high CO2.