Hydroponic Rootboxes. Small rootboxes have been occasionally used to study root growth of (wetland) plants (as related to soil properties) under waterlogged / flooded conditions (e.g. Busch et al. 2006, see Figure). However, hydroponic root boxes are not yet commercially available, hampering research on the "hidden half" of wetland and waterlogged ecosystems. As a result, many studies use pots that only allow measurements of root growth and spatial patterns of soil properties at harvest time. Large tanks with multiple pots of plants have also been used, but often at the expense of lacking independent replicates. In response to customer demand, particularly for potential studies on rice root systems, Vienna Scientific is currently testing reliable and affordable hydroponic rhizobox designs that allow root and soil parameters to be studied under independently flooded conditions. Our goal is to develop a robust, low-cost floodable rootbox design that provides access to roots and soil via a removable (transparent) front and/or back panel, convenient water level adjustment via a drainage system (with side outlets), and a tightly sealed experimental rootbox system that effectively prevents leakage. Stay tuned for details!
The term waterlogging is used to describe the (super)saturation of the soil beyond the field capacity. Except in natural wetlands, waterlogging occurs when the infiltration of water from rainfall or flooding exceeds the rate of drainage and evapotranspiration. Diffusion of gases, particularly O2, is ∼10k-times slower in water than in air, leading to rapid O2 depletion in waterlogged soils - as diffusion fails to keep pace with the respiratory demand of roots and microbes. Oxygen depletion in the root zone therefore has a direct and rapid effect on plant growth by limiting aerobic respiration.
Others, such as mangroves, tap oxygen above the water table by developing special organs. These root morphological, anatomical and/or physiological adaptations can (at least partially) compensate for O2 deficiency in the soil and support aerobic root respiration. Much work has therefore focused on the development and functional role of aerenchymatous roots under waterlogged conditions. On the other hand, the quantification of responses of 'normal' (lateral) roots to waterlogging in 'non-wetland' plants/crops has often been overlooked. This is surprising given that extremes in water availability (both wet and dry) will increase worldwide under future climate conditions, and that many management practices (e.g. heavy machinery for harvesting) increase soil compaction - compaction makes soils more susceptible to waterlogging by reducing pore space. In addition to the direct effects of O2 depletion, many other soil biochemical processes are affected by waterlogging, including major changes in nutrient availability. It is therefore crucial that root and soil processes under temporary waterlogging receive more attention from researchers worldwide. Vienna Scientific aims to provide the technical means - through the development of effective hydroponic rootbox systems - that will enable the easier set-up of studies on the topic.
Roots and Rhizosphere
under Flooded Conditions