Figure 1.

Transverse sections of young root segments (30 mm) from Central Amazon floodplain tree species. For fluorescence microscopical investigations of suberin deposits, root sections were stained with neutral red after quenching of autofluorescence with toluidine blue. a, Aerobically grown root tips from T. juruana. Note that the suberization initiates shortly behind the root tip. Arrow shows initiation of suberization. b through d, Transverse sections of aerobically (b and c) and hypoxically (d) grown roots. Roots of T. juruana are characterized by the presence of small intercellular spaces in the root cortex (b) and a strongly suberized hypodermis (c and d). e through g, Transverse sections of aerobically (e and f) and hypoxically (g) grown roots of L. corymbulosa. e, No air spaces in the root cortex are evident. Suberin staining pattern reveals an incompletely suberized hypodermis with a high number of passage cells. h through j, Transverse sections of aerobically (h and i) and hypoxically (j) grown roots of S. martiana. Cross sections show the formation of large aerenchymatous air spaces in the root cortex (h) and a weak suberin staining of the hypodermal cell layer (i and j). k through m, Transverse sections of aerobically (k and l) and hypoxically (m) grown roots of C. benthami. k, Small intercellular air spaces are present in the root cortex. Staining reveals no suberin deposits in young root segments. Bars = 5 mm (a) and 50 μm (b–m). Eight root segments were analyzed per species and growth type (C. benthami, n = 4).