Leaf area estimation model by length and width method of rose with different genotypes and validity test

【Objective】To study the estimation models of rose leaf area for different genotypes and test their validity， which could provide reference for measuring rose leaf area and constructing digital models of rose growth and development.【Method】Using 6000 leaves of 300 rose varieties as experimental materials，the longest leaf length and widest leaf width of each variety’s rose leaves were measured using a vernier caliper. The actual measured leaf area was obtained using ImageJ image processing software. Based on the coefficient of determination（R²），root mean square error（RMSE）， and normalized root mean square error（NRMSE），7 leaf area models were established to simulate leaf area and fit it to the actual measured leaf area of each variety. Based on the leaf strain，leaf shape and leaf shape coefficient of different genotypes of rose，the classification and model coefficient were calculated.【Result】Among the 7 leaf area estimation models，the simulated leaf area and actual measured leaf area of models 3，4，and 7 were distributed near 1∶1 line，indicating good prediction of rose leaf area. Among them，model 4 had an R² of 0.907，RMSE of 0.726 cm²，and NRMSE of 0.082 cm²，with high accuracy，simplicity，and good universality，suitable for large-scale field measurements. There was no significant difference in the model coefficients between different rose strains（P>0.05）. The average model coefficient of circular leaves was significantly higher than that of oval and elliptical leaves（P<0.05，the same below）. Under the classification of leaves into 7 categories with a leaf shape coefficient of 0.2 intervals，the mean RMSE was 0.863 cm²，which was lower than the classification using a leaf shape coefficient of 0.4 intervals（0.894 cm²）. Randomly selecting 70 rose varieties to validate their leaf area model，the results showed that the average relative error of the leaf area model coefficient based on the leaf shape coefficient factor was 0.499%，indicating that the leaf area model coefficient based on the leaf shape coefficient could be used to determine rose leaf area.【Conclusion】The model formula for calculating rose leaf area with high accuracy and good universality is：leaf area=leaf area×leaf length×leaf width，the leaf shape coefficient with an interval of 0.2 can more accurately reflect the shape characteristics of rose leaves，and the obtained model coefficients have higher accuracy in calculating leaf area.