Root growth of Rumex and Plantago species in compacted and waterlogged soils

The root patterns of Rumex palustris (Sm.), Rumex acetosa (L.) and Plantago major (L.) ssp. major, three species occurring in the river forelands, were studied in experimentally waterlogged or drained compacted soils and compared with specimens growing in drained loosely packed-soils as a control. A modified method for endoscopy in root boxes was developed. The species studied showed different patterns of root development as a result of soil waterlogging or compaction. R. palustris was the least sensitive to waterlogged soils, as shown by the formation of new, morphologically distinctive roots; R. acetosa was the most sensitive and P. major had an intermediate response. With respect to soil compaction P. major was the least affected species, followed by R. acetosa and R. palustris, respectively. The fractional root porosity of these species was studied by using a flow-through system to create hypoxia, a small soil-pore diameter or a combination of both. Hypoxia resulted in a higher root porosity. In both Rumex species small soil-pores inhibited this increase. Contrasting results were found for the porosity of Plantago roots. Results are discussed in relation to the distribution of these species in the field.