Physiological response of sugar beet (Beta vulgaris) genotypes to a temporary water deficit, as evaluated with a multiparameter fluorescence sensor

Greenhouse and field experiments were carried out to evaluate the potential of specific fluorescence emission parameters for the detection of a temporary water deficit in selected sugar beet (Beta vulgaris L.) genotypes. Changes in the plant physiology due to reduced water availability were recorded with a multiparameter fluorescence sensor in addition to destructive and non-invasive reference analysis. Our results show that an insufficient water supply is followed by only slight changes of the UV-excited blue fluorescence. However, significant alterations due to desiccation were detected in several chlorophyll fluorescence parameters measured after excitation with UV, green and red light. In the scope of our activities, the relevance of the green light source for the fluorescence excitation became evident and enabled to characterize cultivar-specific reactions during dehydration and re-watering period. A field experiment was conducted to validate the data collected in the greenhouse. As proven, several days of low water supply led to effects similar to those observed in the greenhouse study. Our results indicate that the far-red fluorescence, as well as the simple and complex fluorescence ratios having the chlorophyll fluorescence as basis, is the appropriate parameter to evaluate physiological responses of sugar beet plants exposed to a short-term, temporary water deficit.