Aerenchyma formation in roots and entry point of oxygen in stems of Syzygium kunstleri grown in hypoxic conditions

Sou, H.-D., Masumori, M., Tange, T., Oh, J.-H.

Aerenchyma formation in roots and entry point of oxygen in stems of Syzygium kunstleri grown in hypoxic conditions

Autores

Sou, H.-D., Masumori, M., Tange, T., Oh, J.-H.

Editor

FAO ;

Descripción

Aerenchyma serves as a low-resistance O2 transport pathway which makes the plant to survive in flooding conditions. When Syzygium kunstleri, tropical swamp woody plant species, is exposed to hypoxic conditions, primary and secondary aerenchyma(PA, SA) develop in stems and roots. The aim of this study is to investigate the development of PA and SA in the adventitious root, and investigate the entry point of O2 in stem of S. kunstleri sapling grown in hypoxic condition. We prepared cross sections of 0.5cm intervals from adventitious root(>10cm) developed in 0.1% agar medium to observe the longitudinal distribution of PA and SA under light and fluorescence microscopes. The entry point of O2 was investigated by measuring the change of oxygen partial pressure(pO2) by Clark-type O2 microelectrode at the adventitious root while changing the position of stem exposed to N2 or air. N2 or air was injected through a 3cm tube which covered the stem. Schizogenous aerenchyma(SCHA) was observed in the root tip, lysigenous aerenchyma(LYSIA) was observed in the upper position of the root, and LYSIA and SA were simultaneously observed in the root base. SA was formed inside the LYSIA, and cortex collapse was observed near the root base. O2 concentrations were controlled by N2 or air injections at the position of stem at 0-3 and 3-6cm above water level. N2 injections at the position of stem at 0-3cm above water level resulted in declines of pO2 in the roots from about 14-15 to 3-4kPa. The change in pO2 in the root was affected by removal of SA in stem under water. Air injection at the position of stem 0-3cm above water level after removal of SA in stem didn't make the recovery of the pO2 in the root from 2-4kPa. The light conditions did not affect the changes of pO2 in the root. SCHA, LYSIA and SA developed in order of age of tissue within each adventitious root. The SA in the stem of S. kunstleri positioned near water surface, was investigated as the entry point for atmospheric O2. Keywords: Sustainable forest management ID: 3623148