Rice yield reduction due to water limitation depends on its severity and duration and on the phenological stage of its occurrence. We exposed three contrasting rice genotypes, IR64, UPLRi7 and Apo (adapted to lowland, upland and aerobic conditions, respectively), to three water regimes (puddle, 100% and 60% field capacity) in pots during the vegetative (GSI), flowering (GSII) and grain filling (GSIII) stages. Stress at all the three stages significantly reduced yield especially in lowland genotype IR64. Effect of water limitation was more severe at GSII than at the other two stages. Stress at GSI stage reduced both source activity (leaf area and photosynthetic rate) and sink capacity (tiller number or panicle number per pot). When stress was imposed at GSII, spikelet fertility was most affected in all the three genotypes. In both GSII and GSIII, although leaf area was constant in all the three water regimes, estimated relative whole-plant photosynthesis was strongly associated with yield reduction. Reduced photosynthesis due to stress at any given stage was found to have direct impact on yield. Compared to the other genotypes, Apo had deeper roots and maintained a better water relation, thus, higher carbon gain and spikelet viability, and ultimately, higher biomass and productivity under water-limited conditions. Therefore, screening for these stage-dependent adaptive mechanisms is crucial in breeding for sustained rice production under water limitation.

由于水分限制而导致的水稻减产取决于其严重性和持续时间以及其发生的物候阶段。在营养（GSI），开花期，我们将三种不同的水稻基因型IR64，UPLRi7和Apo（分别适应低地，旱地和有氧条件）暴露于盆中的三种水分状况（水坑，100％和60％田间持水量）。 （GSII）和谷物填充（GSIII）阶段。这三个阶段的胁迫都显着降低了产量，特别是在低地基因型IR64中。GSII的水分限制效应比其他两个阶段更为严重。GSI阶段的压力降低了源活性（叶面积和光合速率）和库容（分pot数或每盆穗数）。当对GSII施加压力时，在所有三种基因型中，小穗育性受到的影响最大。在GSII和GSIII中，尽管在所有三种水分制度下叶片面积都是恒定的，但估计的相对全株光合作用与减产密切相关。发现在任何给定阶段由于压力而导致的光合作用降低直接影响产量。与其他基因型相比，Apo具有更深的根系并保持了更好的水关系，因此，在缺水条件下，更高的碳获取量和小穗活力，以及最终更高的生物量和生产力。因此，筛选这些阶段相关的适应性机制对于育种在缺水条件下持续水稻生产至关重要。发现在任何给定阶段由于压力而导致的光合作用降低直接影响产量。与其他基因型相比，Apo具有更深的根系并保持了更好的水分关系，因此，在缺水条件下，更高的碳素吸收和小穗活力，以及最终更高的生物量和生产力。因此，筛选这些阶段相关的适应性机制对于育种在缺水条件下持续水稻生产至关重要。发现在任何给定阶段由于压力而导致的光合作用降低直接影响产量。与其他基因型相比，Apo具有更深的根系并保持了更好的水关系，因此，在缺水条件下，更高的碳获取量和小穗活力，以及最终更高的生物量和生产力。因此，筛选这些阶段相关的适应性机制对于育种在缺水条件下持续水稻生产至关重要。