Biology learning, especially the topic of plant physiology, requires Higher Order Thinking Skills (HOTS). This ability needs to be improved with HOTS based teaching materials. The teaching materials, however, have not been developed, especially those in plant physiology topic. Students' HOTS in biology learning still requires an improvement as HOTS is important for the 21st century. One alternative that can be developed is teaching materials in the form of an E-Supplement Book Based on Plant Physiology Research (ESPPRe). The purpose of this study was to measure students' HOTS related to the concept of plant physiology as the basis for developing ESPPRe. The method used was descriptive using a survey technique. The instrument used in this study amounted to 10 items distributed using Google form. The results indicated that the scores were categorized as low for all students (40.81) with male students (41.39) and female students (40.74). This suggested that the HOTS score still needs to be improved and it is necessary to develop ESPPRe in further research. The content on the ESPPRe media that must be developed is related to activities to analyze and criticize problems that have been presented in ESPPRe. Next, students are expected to be able to create solutions and ideas related to these problems. The development of various learning media will make students happier in learning. This is because HOTS-based learning implementation will be varied. This study concludes that the HOTS score is still in the low category and the ESPPRe can be developed in subsequent studies. Suggestion from this research is to be able to implement the book to improve students' abilities to solve problems.