Lateral Roots, In Addition To Adventitious Roots, Form A Barrier To Radial Oxygen Loss In Zea Nicaraguensis And A Chromosome Segment Introgression Line In Maize

Plants typically respond to waterlogging by producing new adventitious roots with aerenchyma and many wetland plants form a root barrier to radial O-2 loss (ROL), but it was not known if this was also the case for lateral roots.We tested the hypothesis that lateral roots arising from adventitious roots can form a ROL barrier, using root-sleeving electrodes and O-2 microsensors to assess ROL of Zea nicaraguensis, the maize (Zea mays ssp. mays) introgression line with a locus for ROL barrier formation (introgression line (IL) #468) from Z. nicaraguensis and a maize inbred line (Mi29).Lateral roots of Z. nicaraguensis and IL #468 both formed a ROL barrier under stagnant, deoxygenated conditions, whereas Mi29 did not. Lateral roots of Z. nicaraguensis had higher tissue O-2 status than for IL #468 and Mi29. The ROL barrier was visible as suberin in the root hypodermis/exodermis. Modelling showed that laterals roots can grow to a maximum length of 74 mm with a ROL barrier, but only to 33 mm without a barrier.Presence of a ROL barrier in lateral roots requires reconsideration of the role of these roots as sites of O-2 loss, which for some species now appears to be less than hitherto thought.