ABSTRACT

Canopy photosynthesis is an important component of biomass production in field-grown rice (Oryza sativa L.). Although canopy temperature differences (CTD) provide important information for evaluating canopy photosynthesis, the measurement of CTD is still a labor-intensive task. Therefore, we designed this study to establish a model for predicting CTD under different field conditions using meteorological data and evaluated the environmental response of CTD using the established model. Our study collected 2,056,264 CTD data points from two rice cultivars having different photosynthetic capacities, ‘Koshihikari’ and ‘Takanari’, and then used these data to create a novel model using a neural network (NN). The input variables were limited to meteorological data, and the output variable was set to CTD. The established NN model produced a prediction accuracy of R² = 0.792 and RMSE = 0.605°C. We then used this NN model to simulate the CTD response of the Koshihikari and Takanari cultivars in response to various environmental changes. These predictions revealed that Takanari had a lower CTD than Koshihikari when exposed to high relative humidity (RH) or low to moderate solar radiation (R_s). In contrast, the CTD of Koshihikari tended to be lower than that of Takanari under lower RH or higher R_s. This result implies that the advantages of the single-leaf gas exchange system in Takanari can be mitigated under extremely high-VPD conditions. Thus, our new method may provide a powerful tool to gain a better understanding of gas exchange, growth processes, and varietal differences in rice cultivated under field conditions.

摘要

冠层光合作用是大田水稻生物量生产的重要组成部分（Oryza sativaL.)。虽然冠层温差 (CTD) 为评估冠层光合作用提供了重要信息，但 CTD 的测量仍然是一项劳动密集型任务。因此，我们设计了这项研究，以建立一个利用气象数据预测不同野外条件下 CTD 的模型，并使用建立的模型评估 CTD 的环境响应。我们的研究收集了来自具有不同光合能力的两个水稻品种“越光”和“高成”的 2,056,264 个 CTD 数据点，然后使用这些数据使用神经网络 (NN) 创建一个新模型。输入变量仅限于气象数据，输出变量设置为 CTD。建立的 NN 模型产生了 R ^{2的预测精度} = 0.792 和 RMSE = 0.605°C。然后，我们使用这个 NN 模型来模拟 Koshihikari 和 Takanari 品种对各种环境变化的 CTD 响应。这些预测表明，当暴露于高相对湿度 (RH) 或低至中等太阳辐射 ( Rs )时，Takanari 的 CTD 低于 Koshihikari _。相比之下，在较低 RH 或较高R _s下，越光的 CTD 往往低于 Takanari 的 CTD 。这一结果表明，Takanari 单叶气体交换系统的优势可以在极高 VPD 条件下得到缓解。因此，我们的新方法可能为更好地了解田间条件下种植的水稻的气体交换、生长过程和品种差异提供了一个强大的工具。