The effect of temperature stress on photosynthesis in Heliotropium thermophilum

In this study, the relationship between high temperature and photosynthesis was investigated in Heliotropium thermophilum (Boraginaceae), a flowering, endemic and thermophilic plant. The plants were obtained from Aydın Buharkent geothermal area. Plants growing at 20-30 °C -portion of the geothermal area were considered as control group, while the plants growing at 55-65 °C were named as experimental group. Physiological analyzes were done in two different growth periods including before and after flowering. To detect the effect of high temperature on photosynthesis in Heliotropium thermophilum, for this purpose, water potential, lipid peroxidation, cell membran stability and H2O2 analysis were carried out so that stress levels on leaves could be determined. In addition, chlorophyll and starch contents, chlorophyll fluorescence, photosynthetic gas exchange parameters, some of photosynthetic enzymes (rubisco and invertase) were measured. After the studies to determine the stress level, no change was determined. Based on these results, it was understood that the plant was tolerant to heat stress. In addition, a general increase in all chlorophyll fluorescence parameters except for Fv/Fm were observed. Fv/Fm did not change. Increase in photosynthetic gas exchange parameters, starch content, rubisco and invertase acitivities were also observed. It was determined that a certain degree of stress did not affect photosynthetic efficiency at high temperature and H. thermophilum protected the photosynthetic units under high temperature conditions