Split-root systems: detailed methodology, alternative applications, and implications at leaf proteome level

BACKGROUND

Split-root systems (SRS) have many applications in plant sciences, but their implementation, depending on the experimental design, can be difficult and time-consuming. Additionally, the system is not exempt from limitations, since the time required for the establishment of the SRS imposes a limit to how early in plant development experiments can be performed. Here, we optimized and explained in detail a method for establishing a SRS in young Arabidopsis thaliana seedlings, both in vitro and in soil.

RESULTS

We found that the partial de-rooting minimized the recovery time compared to total de-rooting, thus allowing the establishment of the split-root system in younger plants. Analysis of changes in the Arabidopsis leaf proteome following the de-rooting procedure highlighted the distinct metabolic alterations that totally and partially de-rooted plants undergo during the healing process. This system was also validated for its use in drought experiments, as it offers a way to apply water-soluble compounds to plants subjected to drought stress. By growing plants in a split-root system with both halves being water-deprived, it is possible to apply the required compound to one half of the root system, which can be cut from the main plant once the compound has been absorbed, thus minimizing rehydration and maintaining drought conditions.

CONCLUSIONS

Partial de-rooting is the suggested method for obtaining split-root systems in small plants like Arabidopsis thaliana, as growth parameters, survival rate, and proteomic analysis suggest that is a less stressful procedure than total de-rooting, leading to a final rosette area much closer to that of uncut plants. Additionally, we provide evidence that split root-systems can be used in drought experiments where water-soluble compounds are applied with minimal effects of rehydration.

High water uptake ability was associated with root aerenchyma formation in rice: Evidence from local ammonium supply under osmotic stress conditions

Root water uptake is strongly influenced by the morphology and anatomical structure of roots, which are regulated by nitrogen forms and environmental stimuli. To further illustrate the roles of different nitrogen forms on root water uptake under osmotic stress, a split-root system was supplied with different nitrogen forms and osmotic stress simulated by adding 10% (w/v) polyethylene glycol (PEG, 6000). The local effects of nitrogen form and osmotic stress on root morphology, anatomical structure, root lignin content, and water uptake rate were investigated. Under osmotic stress conditions, ammonium markedly promoted the formation and elongation of the lateral root, whereas a significant decrease in numbers of lateral roots was observed under local nitrate supply. Under nitrate supply in split-root systems, osmotic stress significantly promoted root cell death and more aerenchyma formation, as well as accelerated the lignification of the root. However, osmotic stress had no negative effect on the root anatomical structure under ammonium supply. The root water uptake rate was significantly higher in split-root supplied with ammonium than nitrate under osmotic stress conditions. In conclusion, the high water uptake ability in local ammonium supply was associated with the more lateral roots development and the lower cell death, aerenchyma formation and lignification under osmotic stress.