Abstract BACKGROUND Understanding root architectural plasticity under water deficit is essential for improving rice drought tolerance. However, whether drought‐tolerant and drought‐sensitive cultivars differ in qualitative spatial strategies or merely in the magnitude of plastic responses remains unresolved, and conventional destructive phenotyping cannot capture three‐dimensional dynamics. RESULTS We developed WSroots, an L‐system‐based three‐dimensional model, and quantified root development in drought‐tolerant HY73 and drought‐sensitive Longliangyou Huazhan (LLYHZ) under polyethylene glycol‐6000 (PEG6000) osmotic stress at 0, 50, 125 and 200 g kg −1 for 28 days in hydroponic culture. HY73 maintained 25–30% of root length at 35–60 cm depth with only 25.2% total length reduction at 200 g kg −1 PEG6000, whereas LLYHZ concentrated 65–70% of roots in the 0–15 cm surface layer with 39.6% reduction. Root diameter declined less in HY73 (9.3%) than in LLYHZ (14.8%), indicating superior structural resilience. Calibration accuracy reached a coefficient of determination ( R 2 ) of 0.986 (HY73) and 0.949 (LLYHZ). CONCLUSION The two cultivars employ qualitatively distinct strategies – deep exploration versus shallow expansion – rather than quantitative gradients of the same response. Deep‐rooting maintenance is therefore a key target for drought‐resilient rice breeding. WSroots provides a transferable framework for virtual phenotyping and irrigation design that can be extended to soil‐based systems through water potential equivalence. © 2026 Society of Chemical Industry.
Yang et al. (Tue,) studied this question.