Utilization of Enfrared Thermography and Leaf Reflectance Indices in Evaluation of Effects of the Treatment of Sunflower (Helianthus annuus L.) by Biologically Active Compounds | Využitie infračervenej termografie a indexov reflektancie listu v hodnotení účinku ošetrenia slnečnice ročnej (Helianthus annuus L.) biologicky aktívnymi látkami

The effects of biologically active compounds (Route and Sunagreen) on physiological fitness of three sunflower hybrids (NK Kondi, NK Dolbi a NK Tristan) were carried out during the whole growing season in vegetation polyfactorial experiments. Evaluation of the sunflower physiological fitness was realized by non-destructive technique of measuring the temperature difference (AT) with an infrared thermography and simultaneous measurement of the leaf reflectance indices NDVI (normalized difference vegetation index) and PRI (photochemical reflectance index). Inthispaperwe discuss the ontogenetic changes in the parameters AT, NDVI and PRI with emphasis on changes in weather conditions. We also investigated the potential effects of foliar applied biologically active compounds on plants and sensitivity of sunflower hybrids to their application. The results confirmed the typical ontogenetic changes of individual assessment parameters that reflect the physiological processes of plant during the growing season. In this vegetation period which was characterized by high precipitation in summer, the most sensitive measure parameter was AT. All sunflower hybrids significantly (p lt 0.05) responded to the treatment by Route, particularly in the reproductive stage of ontogeny (in treatment by Route the average AT was -4.5 to -5.2 deg C and in untreated plants -2.3 to -3.8 deg C). This result indicates a greater cooling effect of transpiration and thus a higher stomatal conductivity induced by Route treatment. Sunflower plants treated by Sunagreen showed in AT statistically significant response only in hybrid NK Tristan at the last phase of ontogeny. Reflectance indices NDVI and PRI, which correlate with the photosynthetic efficiency of plants, were proved as the less sensitive parameters describing the effects of biologically active substances on sunflower hybrids. Results showed that the PRI index increased during plant ontogeny with a subsequent decrease in the maturing of achenes but we did not observe the statistically significant positive effects of biologically active substances on physiological fitness of sunflower hybrids.