Responses of Barnyardgrass (Echinoch/oa crux galli (L) Beauv. var. curs galli) to Water Drained, Saturated and Flooded Soils in Root Aerenchyma Formation*

Responses of barnyardgrass (Echinochloa crus-galli var. crux-galli) to water drained, saturated, or flooded soils were assessed in relation to the aerenchyma formation in crown roots. Plant height, fresh weight of shoots, the number of crown roots, and the fresh weight of roots of 4-week-old barnyardgrass increased in the following order: saturated>drained>flooded. By contrast, aerenchyma was radially well developed in the cortex of crown roots when flooded, but no extensive aerenchyma formation was observed when the soil was drained. Both root porosity and the total area of aerenchyma increased in the following order: flooded>saturated>drained; however, these values varied with the portion and/or ages of crown roots tested. In relation to the diameter of the crown roots, barnyardgrass showed different responses from those of root aerenchyma, i. e., the root diameter increased significantly when the soil was saturated but decreased as the root aged. These results suggest that the response to flooding in Barnyardgrass is related to the formation of root aerenchyma which developed in a polar direction from the basal parts to the apical parts as the roots aged.