Effects of heat stress on Euphorbia peplus growth in hydroponics and subsequent ingenol production

Plant secondary metabolites (PSM) are phytochemicals with high relevance to the pharmaceutical and food industries. The accumulation of PSM occurs often under stress as a protective and/or adaptive mechanism. Environmental factors such as temperature, relative humidity, fertilization, light intensity, and atmospheric CO2 concentration have all separately a significant impact on plant growth and PSM production. Therefore, the purpose of this study is to examine the effects of heat stress on Euphorbia peplus growth and the subsequent ingenol production. Then, three temperature levels (18, 24, 30°C) were applied. Plants were cultivated in controlled environment chambers using a hydroponic system. Harvesting was conducted over three distinct periods (30 days, 45 days and 60 days). Throughout the crop, agronomic measurements were made (plant height, dry weight percentage), as well as an UPLC analysis of ingenol plant content. In response to heat stress (30°C), the plant's height decreased between the 45th and 60th day of cultivation, the plant bends over and loses leaves. In opposite, the plant's height carried on to increase at 18 and 24°C for all the periods of observation. At 30°C, the plants accumulated more dry matter after 45 and 60 days than the plants grown at other temperatures with a higher plant content of ingenol.