Minirhizotron observation of pigeonpea root system after waterlogging

The root growth of pigeonpea plants [Cajanus cajan (L) Millsp.] was studied with a micro-video camera inserted into a glass tube embedded in the soil, and the effects of soil waterlogging were quantified. Daily changes in root length density (RLD) and the differences in root growth between waterlogged and control plants were calculated by adopting curve-fitting into the time-course data of RLD. Roots which suffered from waterlogging exhibited higher daily changes in RLD during the recovery process than unstressed roots. After waterlogging, an increase in RLD was first observed in the upper soil layers, and then in progressively deeper layers. This study demonstrates that root growth can be successfully studied by frequent observations of the same soil-plant interface through glass tubes. Furthermore, the effects of waterlogging can be adequately studied using this technique.