Oxygen in the air and oxygen dissolved in the floodwater both sustain growth of aquatic adventitious roots in rice

Flooding is an environmental stress that leads to a shortage of O-2 that can be detrimental for plants. When flooded, deepwater rice grow floating adventitious roots to replace the dysfunctional soil-borne root system, but the features that ensure O-2 supply and hence growth of aquatic roots have not been explored. We investigate the sources of O-2 in aquatic adventitious roots and relate aerenchyma and barriers for gas diffusion to local O-2 gradients, as measured by microsensor technology, to link O-2 distribution in distinct root zones to their anatomical features. The mature root part receives O-2 exclusively from the stem. It has aerenchyma that, together with suberin and lignin depositions at the water-root and cortex-stele interfaces, provides a path for longitudinal O-2 movement toward the tip. The root tip has no diffusion barriers and receives O-2 from the stem and floodwater, resulting in improved aeration of the root tip over mature tissues. Local formation of aerenchyma and diffusion barriers in the mature root channel O-2 towards the tip which also obtains O-2 from the floodwater. These features explain aeration of floating roots and their ability to grow under water.

Automated summary

Research has shown that aquatic adventitious roots are able to grow underwater in flooded environments due to their unique structures that provide a sufficient oxygen supply.