D‐Root: a system for cultivating plants with the roots in darkness or under different light conditions

Abstract

SUMMARYIn nature roots grow in the dark and away from light (negative phototropism). However, most current research in root biology has been carried out with the root system grown in the presence of light. Here, we have engineered a device, called Dark-Root (D-Root), to grow plants in vitro with the aerial part exposed to the normal light/dark photoperiod while the roots are in the dark or exposed to specific wavelengths or light intensities. D-Root provides an efficient system for cultivating a large number of seedlings and easily characterizing root architecture in the dark. At the morphological level, root illumination shortens root length and promotes early emergence of lateral roots, therefore inducing expansion of the root system. Surprisingly, root illumination also affects shoot development, including flowering time. Our analyses also show that root illumination alters the proper response to hormones or abiotic stress (e.g. salt or osmotic stress) and nutrient starvation, enhancing inhibition of root growth. In conclusion, D-Root provides a growing system closer to the natural one for assaying Arabidopsis plants, and therefore its use will contribute to a better understanding of the mechanisms involved in root development, hormonal signaling and stress responses.

Organ specificity in the plant circadian system is explained by different light inputs to the shoot and root clocks

“…Silva‐Navas et al . (2015) have also noted that the responses of root length to direct illumination depend on light quality and that several photoreceptors are involved in these responses. However, our work does not exclude other potential differences between the two clocks apart from light inputs.…”

Light Signaling, Root Development, and Plasticity

“…1). Phyb mutants have been shown to produce fewer lateral roots (Salisbury et al, 2007), and Phyb and Phya single and double mutants have reduced root elongation compared with the wild type (Correll and Kiss, 2005;Silva-Navas et al, 2015). Recently, PhyB has been identified to act as a temperature sensor (Jung et al, 2016;Legris et al, 2016), which is interesting since heat stress is known to lead to increased main root growth (Hanzawa et al, 2013).…”

“…Supplementation of white light with FR light reduces root growth compared with normal white light (Salisbury et al, 2007;Fig. 2), and UVB has a strong inhibiting effect on root growth, either when supplied to the whole seedling or only the root (Tong et al, 2008;Leasure et al, 2009;Silva-Navas et al, 2015).…”

“…In field conditions, the top part of the root system will grow in minimal light and the lower part will even develop in darkness, while the shoot can be exposed to various different light conditions (Smith, 1982). Several solutions to these undesirable lab conditions have been postulated, including dark agar plugs (Sassi et al, 2012), black-colored vertical plates , and the D-Root system consisting of plate inserts plus cover slips (Silva-Navas et al, 2015). In the D-Root system, seedlings grow on medium in vertical square plates, but an insert at the root-shoot junction and an external cover slip prevent light exposure of the roots, whereas the shoot is exposed to the ambient light conditions.…”

Light Sheet Fluorescence Microscopy of Plant Roots Growing on the Surface of a Gel

“…the roots are exposed to light. This may cause different responses to their environment and induces changes in their biochemistry and development 26,27 . In order to reduce the amount of light on the root system, black plastic foil was used to cover the water surface as well as a lid made of black aluminum foil covered the sample chamber.…”