Persistent adventitious and basal root development during salt stress tolerance in Echinocactus platyacanthus (Cactaceae) seedlings

Abstract

Echinocactus platycanthus is a remarkable globular cacti that can reach sizes up to 2 m in diameter, and is known for its high tolerance to salt stress, as they inhabit arid environments where salinity is prominent. Understanding the early developmental events of salt tolerance and stress responses will help understand how seedlings establish in arid environments. Thus, we asked how E. platyacanthus seedlings face continuous and prolonged exposure to high salinity concentrations, focusing in particular on the developmental responses of the root system architecture. We used 13 days old seedlings grown in vitro, in media supplemented with NaCl at toxic concentrations for many plants. Seedlings can withstand highly toxic salt concentrations and survival was not compromised. As expected, continuous and prolonged salt stress reduced root system architecture growth. However, adventitious and basal root development persisted in salt stressed seedlings, while main root growth was inhibited and epicotyl elongation was stunted. Adventitious and basal root proliferation might be an important component of tolerance to prolonged salt stress, and possibly crucial for the establishment of seedlings of E. platyacanthus in the wild.