Orthosiphon aristatus (Java Tea) is a traditional and socioeconomically valuable medicinal plant with different pharmaceutical activities for preventing and treating various diseases. Air temperature is one of the environmental elements that have an impact on plant growth and yield production. This study aimed to assess how Java tea plants respond to high air temperatures and to learn if compost amendment may have a substantial impact on plant growth and yield. This research was arranged using a completely randomized design (CRD), with air temperature as the main factor, and three replicates for each treatment. Java tea plants were maintained in the greenhouse (control) for 3 months and in the growth chamber day/night temperatures of 25°C, 30°C, 35°C, 40oC, 45oC and 50/25oC. Overall, the plants placed in growth chamber conditions have significantly demonstrated the optimal growth and yield of observed parameters than greenhouse treatments. Java tea plants kept at 30/25°C and 35/25°C had considerably higher plant height, leaf numbers, fresh and dry weight values than other treatments, whereas the 40oC treatments had the greatest growth decline, reduced in leaf number, fresh, and dry weight. Moreover, all plants subjected to 45/25°C and 50oC/25oC suffered more severe up to mortality. This research confirmed the positive and significant increase of total phenolic (TP), total flavonoid (TF) and antioxidant bioactive contents increased as temperature increased. Moreover, compost soil amendment was affected significantly the total phenols, total flavonoids and antioxidant secondary metabolites contents than the treatments without compost. Thus, the 35oC treatment recorded higher total flavonoids (23.86 mg QE/ 100 g DW) and 40oC treatments revealed higher total phenols and antioxidant contents (18.70 mg GAE/ 100 g DW; 40.95 ?mol TE/g DW) respectively. This study demonstrated that temperature control technology would be more beneficial for the high marketability of plant-based medicines that can enhance biomass and secondary metabolite production.
