Abstract:

Aims We investigated aerenchyma formation in stems of riparian plants Arundinella anomala and Salix variegata as affected by addition of ethylene and α-naphthalene acetic acid (α-NAA) under non-flooded conditions in order to ascertain whether phytohormone ethylene and auxin are direct stimuli for aerenchyma formation in flooded plants.

Methods Our experiment included treatments of ethylene (0, 250, 500 mg·L^-1), α-NAA (0, 50, 100 mg·L^-1) and joint addition of ethylene and α-NAA (250 mg·L^-1+50 mg·L^-1) for A. anomala and S. variegata plants. Five days following hormone additions, we obtained transverse sections of mid-stems of A. anomala and S. variegata and analyzed aerenchyma formation using E80i Nikon microscope, ACT-2U and Simple PCI software.

Important findings Aerenchyma formation was enhanced when plants were irrigated with either ethylene or α-NAA. Moreover, aerenchyma formation increased with hormone concentration. Aerenchyma formation was enhanced when plants were irrigated with a mixture of ethylene (250 mg·L^-1) and α-NAA (50 mg·L^-1), but it did not differ from aerenchyma formation induced by either ethylene addition of 250 mg·L^-1 or α-NAA addition of 50 mg·L^-1. Our work demonstrates that, in flooded environments, the aerenchyma formation in plant stems is directly related to increases of ethylene and auxin, and flooding may not be the direct stimulus for the formation of aerenchyma.

Key words: Arundinella anomala, aerenchyma, ethylene, α-naphthalene acetic acid, Salix variegate, Three Gorges Reservoir Region