Table I. Experiments conducted and traits considered in this study.
Ave root diam, Average root diameter; CT, canopy temperature; DTF, days to 50% flowering; gS, stomatal conductance; GY, grain yield; L, lowland; LDS, lowland drought stress; %LR, percentage lateral root (>60 cm); LRW, lowland rewatered; NS, nonstress (control); PHT, plant height; Plas, plasticity; RDW, root dry weight; RGR, relative growth rate from 24 to 31 d after sowing (DAS); RL, root length; RLD, root length density; R/S, root-shoot ratio; S, stress; SDW, shoot dry weight; SL, shoot length; TWU, total water uptake; U, upland; UDS, upland drought stress; URW, upland rewatered.
| Study | Treatment | Env. Code | Date of Planting/Transplanting | Observed Traits |
|---|---|---|---|---|
| Lysimeter | Lowland drought stress | LDS stress | August 17, 2012/August 29, 2012 | TWU, maximum root depth, SDW, RDW (0–20, 20–40, 40–60, and >60 cm), R/S, Ave root diam (>60 cm), RLD (>60 cm), %LR (>60 cm), forks (>60 cm), Plas RDW (0–20, 20–40, 40–60, and >60 cm), Plas %LR (0–20, 20–40, 40–60, and >60 cm) |
| Lowland rewatered | LRW stress | August 17, 2012/August 29, 2012 | ||
| Lowland control (for LDS) | LDS control | August 17, 2012/August 29, 2012 | TWU, maximum root depth, SDW, RDW (0–20, 20–40, 40–60, and >60 cm), R/S, Ave root diam (>60 cm), RLD (>60 cm), %LR (>60 cm), forks (>60 cm) | |
| Lowland control (for LRW) | LRW control | August 17, 2012/August 29, 2012 | ||
| Direct-seeded upland drought stress | UDS stress | August 17, 2012 | TWU, maximum root depth, SDW, RDW (0–20, 20–40, 40–60, and >60 cm), R/S, Ave root diam (>60 cm), RLD (>60 cm), %LR (>60 cm), forks (>60 cm), Plas RDW (0–20, 20–40, 40–60, and >60 cm), Plas %LR (0–20, 20–40, 40–60, and >60 cm) | |
| Direct-seeded upland rewatered | URW stress | August 17, 2012 | ||
| Direct-seeded upland control (for UDS) | UDS control | August 17, 2012 | TWU, maximum root depth, SDW, RGR, RDW (0–20, 20–40, 40–60, and >60 cm), R/S, Ave root diam (>60 cm), RLD (>60 cm), %LR (>60 cm), forks (>60 cm) | |
| Direct-seeded upland control (for URW) | URW control | August 17, 2012 | ||
| Field agronomic | Direct-seeded upland nonstress | 2012UNS | January 3, 2012 | GY, DTF, PHT |
| Direct-seeded upland stress | 2012US | January 6, 2012 | ||
| Direct-seeded upland nonstress | 2013UNS | December 20, 2012 | ||
| Direct-seeded upland stress | 2013US | January 22, 2013 | ||
| Lowland control | 2012LNS | December 10, 2011/January 5, 2012 | ||
| Lowland stress | 2012LS | December 20, 2011/January 14, 2012 | ||
| Lowland stress (Kali Aus population only) | 2013LS | December 19, 2012/January 7, 2013 | ||
| Field physiology | Direct-seeded upland nonstress | 2013UNS phys | December 17, 2013 | RLD, %LR, forks, Ave root diam, RDW (0–15, 15–30, 30–45, and 45–60 cm), GY |
| Direct-seeded upland stress | 2013US phys | December 17, 2013 | CT, gS, soil water potential, RLD, %LR, forks, Ave root diam, RDW (0–15, 15–30, 30–45, and 45–60 cm), Plas RLD (0–15, 15–30, 30–45, and 45–60 cm), Plas %LR (0–15, 15–30, 30–45, and 45–60 cm), Plas RDW (0–15, 15–30, 30–45, and 45–60 cm), GY | |
| Rhizoscope | Control phosphorus | P | July 8, 2013 | RL in rhizobox, root number >30 cm, root number >20 cm, shoot length, tiller number, SDW, RDW (0–15, 15–30, and >30 cm), R/S, Ave root diam, root angle |
| Low phosphorus | P/8 | July 8, 2013 | RL in rhizobox, RL, root number >30 cm, root number >20 cm, tiller number, SL, SDW, RDW (0–15, 15–30, and >30 cm), R/S, Ave root diam, root angle, Plas RL in rhizobox, Plas RL, Plas root number >30 cm, Plas root number >20 cm, Plas tiller number, Plas SL, Plas SDW, Plas RDW (0–15, 15–30, and >30 cm), Plas total root dry weight, Plas R/S, Plas Ave root diam, Plas root angle |