The researchers studied how different plant indices can help estimate leaf area in rice plants. They measured the reflectance of rice fields and compared it to the actual leaf area. They found that certain indices, like RVI and R 810/R 560, were better at estimating leaf area than others like NDVI and SAVI. The best estimate came from the ratio of near infrared to green bands. This method was accurate in predicting leaf area in rice plants, especially during different growth stages and nitrogen levels.