Table 3.
Strategies and approaches for root phenotyping.
| Plant Cultivation System | Growth Media | Description | References |
|---|---|---|---|
| 1. Growth and luminescence observatory for roots (GLO-Roots) | Soil (lab) | This method combines custom-made growth vessels and new image analysis algorithms to non-destructively monitor RSA development over space (2-D) and time. The technique allows information on soil properties (e.g., moisture) to be integrated with root growth data. The system makes use of luminescence imaging of roots expressing plant codon-optimize luciferase. | [96] |
| 2. X-Ray computed tomography | Soil (lab and greenhouse) | Non-destructively visualizes opaque root structures by measuring the attenuation of ionizing radiation as it passes through the root. A series of projections are acquired and combined to reconstruct a 3D image of the root system. | [97,98] |
| 3. Rhizophonics | Liquid media (lab) | Combines hydroponics and rhizotrons. System is made of a nylon fabric supported by an aluminum frame. The set-up is immersed in a tank filled with liquid media. Allows non-destructive, 2-D imaging of root architecture while simultaneously sampling shoots. | [99] |
| 4. Clear pot method | Soil (greenhouse) | Uses transparent pots filled with soil or other potting media. Seeds are planted close to the pot wall to enable high- throughput imaging of roots along the clear pot wall. To prevent light exposure, the clear pot is placed in black pots while roots are developing. | [100] |
| 5. Rhizoslides | Paper-based (lab, greenhouse) | The set-up consists of a plexiglass sheet covered with moistened germination paper. Seeds are planted on the slit of the plexiglass. The system allows separation of crown roots from embryonic roots. | [101] |
| 6. Shovelomics | Soil (field-based) | Involves manual excavation of plants and separating roots from the shoots. Washed roots are then placed on a phenotyping board for root trait quantification. New algorithms allow extraction of several root traits in a high throughput manner. | [94,95] |
| 7. Soil coring | Soil (field-based) | Uses a tractor-mounted, hydraulic soil corer to drive steel alloy sampling tubes into the soil. When combined with novel planting configurations (e.g., hill plots), this method allows for phenotyping deep rooted crop varieties. | [102] |
| 8. Rhizolysimeters | Soil (field-based) | Elaborate facility consisting of an underground corridor and concrete silos and pipes to house soil-containing soil cores for direct root observation. | [103] |
| 9. Minirhizotrons | Soil (field-based) | A transparent observation tube permanently inserted in the soil. Images of roots growing along the minirhizotron wall at particular locations in the soil profile can be captured over time. | [104,105] |