Biomass‐based root morphological parameter models of rice ( <i>Oryza sativa</i> L.) under different drought intensities and drought durations in juvenile differentiation stage

Abstract Quantitative morphological parameters of the rice root system under drought stress in juvenile differentiation stage is pivotal for optimizing water management and breeding of drought‐tolerant varieties in rice ( Oryza sativa L.). This study aims to quantify responses of rice root morphological parameters to varying drought intensities (DI) and durations (DD) in juvenile differentiation stage by proposing a novel drought impact factor, including IF Bi‐DI (drought impact factor for total biomass under drought intensity), IF Bi‐DD (drought impact factor for total biomass under drought duration), IF RBi‐DI (drought impact factor for root biomass under drought intensity), and IF RBi‐DD (drought impact factor for root biomass under drought duration). Pot experiments were conducted during 2018 and 2019 rice growing seasons using two rice cultivars. Nanjing 9108 (conventional) and Huaidao 5 (hybrid), under different DI (including T1, T2, T3, and T4—four levels) and DDs (including W1, W2, W3, W11, and W12—five levels). The results showed that the ratio of scanned root length to the scanned root biomass, and the partition coefficient of total root biomass followed exponential functions, while the partition coefficient of scanned root biomass exhibited an S‐curve relationship. IF Bi‐DI , IF Bi‐DD , IF RBi‐DI , and IF RBi‐DD correlated linearly and logarithmically with time index, respectively. Root surface and volume models adhered to S‐curve functions, whereas root average diameter displayed a linear decline with root length. The validation of models developed by us demonstrated strong correlations between simulated and observed values ( r &gt; 0.73, p &lt; 0.001), with mean absolute difference ( d a ) and root mean square errors consistently below 5% and 6.095 g plant −1 , respectively. This study establishes first biomass‐driven framework to predict root morphological parameters under drought stress in juvenile differentiation stage, offering breeders actionable insights for developing drought‐resilient cultivars and enabling precision irrigation strategies to mitigate yield losses in water‐limited environments.