Modeling of summer maize transpiration considering morphogenesis

Plant transpiration research is the foundation for improving the efficiency of agricultural water resource utilization and ensuring food production safety. It is an important content of agricultural production and water resource utilization research. However, spatial heterogeneities of leaf size and positions affect the estimation of transpiration. In this study, summer maize on the North China Plain was taken as the research object. Based on the measured data of the photosynthetic apparatus, morphogenesis and stem flow meter, the transpiration variation rule of summer maize leaves was analyzed, and the spatial distribution model of photosynthetically active radiation based on plant morphogenesis was constructed. Considering the spatial heterogeneities of leaf size and positions, the individual-plant scale transpiration model was upgraded. The reliability of transpiration model at individual plant scale was verified. The results showed that: i) the transpiration rate of leaves with different leaf positions, positive and negative leaves at the same leaf position and different parts of the same leaf were significantly different. ii) Based on the measured data, the structure of summer maize with spatial coordinates was obtained, and a calculation model for solar radiation reaching the top of the plants and a calculation model for photosynthetically active radiation reaching the surface of the leaves were constructed. Based on the different absorption, reflection, and transmission of radiation by summer maize leaves, the photosynthetically active radiation of each part of the leaves was characterized. iii) A plant transpiration model was constructed by combining the leaf panel transpiration model with the spatial distribution model of photosynthetically active radiation in summer maize plants, and, the determination coefficients between the simulated and the measured values of the individual plant scale transpiration rate were all above 0.95, the consistency index was close to 1.0, and the RMSE was in range of 12.41–16.64 g h−1. The individual plant transpiration obtained after simulated accumulation could meet the simulation accuracy. The results achieved the scale improvement of the leaf transpiration to individual plant transpiration.