Impacts of photoautotrophic, photomixotrophic, and heterotrophic conditions on the anatomy and photosystem II of in vitro-propagated Aechmea blanchetiana (Baker) L.B. Sm. (Bromeliaceae)

Abstract

In vitro culture conditions have a major impact on the physiology and anatomy of micropropagated plants. Sucrose plays a very important role in micropropagation protocols, and is frequently employed during in vitro culture. However, it may induce disorders that negatively interfere with plant growth and development, such as a low photosynthetic rates. The aim of this study was to analyze the impacts of in vitro conditions on the anatomy and photosynthetic performance of Aechmea blanchetiana (Baker) L.B. Sm. Plants previously grown in vitro were transferred to culture media containing 0, 15, 30, or 45 g L−1 sucrose. Two different culture container sealing systems were tested: lids with a filter (permitted gas exchange), and with a PVC-covered filter (blocking fluent gas exchange). Plants grown with exogenous sucrose displayed anatomical traits that could decrease mineral and carbohydrate uptake from the medium. Plants cultured under photoautotrophic conditions had a thinner exodermis and the highest number of metaxylem vessels in the roots. This positively impacted the plant growth and physiological status. Sucrose induced plants with photosystem II (PS II) disorders, such as a lower number of active reaction centers. Under photoautotrophic conditions, there was an increase in absorbed energy flux per cross section (ABS/CSm), and energy transport flux (ETo/CSm), followed by a decrease in the energy dissipation flux (DIo/CSm). This indicated a high PS II efficiency, according to the performance index (PI(ABS)). The use of sucrose can induce physiological disorders in A. blanchetiana plants during in vitro propagation. Photoautotrophic conditions induce plants without anatomical disorders, and positively influence PS II efficiency.