Effects of 6-benzylaminopurine on photosystem II functionality and leaf anatomy of in vitro cultivated Aechmea blanchetiana

Cytokinins (CKs) are often used during the in vitro cultivation of plant species. However, it is not clear how CKs, such as 6-benzylaminopurine (BAP), affect photosystem PS) II functionality and leaf anatomy over a long period of in vitro plant propagation. The aim of this study was to analyze the residual effects of BAP on the photosynthetic performance and leaf anatomy of Aechmea blanchetiana after 120 d without exposure to CKs. Aechmea blanchetiana plants previously grown in vitro were transferred to Murashige and Skoog (MS) culture media containing 0, 5, 10, 15, or 20 μM BAP. After 60 d on the MS medium with BAP, explants were subcultivated twice on the MS medium without growth regulators, first in a stationary liquid medium for 60 d and then in a solidified medium with 6 g dm -3 agar for 60 d. Leaf anatomy, pigment content, and chlorophyll a fluorescence were assessed for plants from each treatment after 120 d on the CK-free medium. Stomatal density presented a negative linear correlation with BAP concentration. Pigment content decreased in plants subjected to previous BAP exposure. An increase in absorbed energy flux per reaction center (ABS/RC) and a sharp decrease in energy transport flux (ETo/RC) followed by an increase in energy dissipation flux (DIo/RC) also occurred. Furthermore, maximum quantum yield (F V /F M ) decreased as a function of BAP concentration. Thus, the use of BAP during in vitro propagation of A. blanchetiana induced long-term physiological defects.