An estimation of canopy photosynthetic activities is needed in order to better understand biomass production of field crops. Thermal imaging techniques and the heat balance model enable us to estimate canopy diffusive conductance (g_c) and canopy transpiration rate (E) of crops under field conditions. However, because conventional methods are unstable when wind velocity is very low, it is difficult to apply this model directly to field-grown crops. In this study, we modified the conventional model by measuring aerodynamic resistance in rice (Oryza sativa (L.)) under windless conditions (r_a∗). The r_a∗ ranged from 9.50 to 35.40 s m⁻¹ among the genotypes. By introducing the concept of r_a∗ to the original heat balance model, the stability when wind velocity is under 3.0 m s⁻¹ improved greatly. Using seven rice genotypes, we evaluated genotypic differences in E with higher temporal resolution. The daily cumulative transpiration ranged from 2.32 kg m⁻² d⁻¹ to 10.29 kg m⁻² d⁻¹ depending on genotype and weather conditions. High-yielding cultivars consistently showed greater transpiration rates under various weather conditions. We confirmed the relationship between estimated E and final grain yield, especially during the daytime. Our modified model is useful as a monitoring tool for rice canopy transpiration.

为了更好地了解田间作物的生物量生产，需要估算冠层的光合活动。热成像技术和热平衡模型使我们能够估计田间条件下农作物的冠层扩散导度（g _c）和冠层蒸腾速率（E）。但是，由于传统方法在风速非常低时不稳定，因此很难将此模型直接应用于田间种植的农作物。在这项研究中，我们通过在无风条件下（r _a ∗）测量水稻（Oryza sativa（L.））的空气动力学阻力来修改常规模型。所述ř_一个*范围从9.50到35.40 S M ^-1在基因型之间。通过将r _a＊的概念引入原始的热平衡模型，风速在3.0 m s ^-1以下时的稳定性大大提高。使用七种水稻基因型，我们以较高的时间分辨率评估了E中的基因型差异。每天的累积蒸腾量取决于基因型和天气状况，从2.32 kg m ^-2  d ^-1到10.29 kg m ^-2  d ^-1。在各种天气条件下，高产品种始终表现出更高的蒸腾速率。我们确认了估计E之间的关系和最终的谷物产量，尤其是在白天。我们修改后的模型可用作水稻冠层蒸腾的监测工具。