The role of the sink tissue in variegated Pelargonium zonale under excess excitation energy pressure morphologic, photosynthetic and metabolic study

In the global warming era, we are facing extreme changes in environmental conditions such as high and low temperatures, high light and ultraviolet radiation intensity, as well as drought and increased CO2 levels. The effects of these factors on plants are often interrelated and usually result in a disturbed balance between the amount of energy received and the ability to process it. In order to balance energy input and prevent photooxidative damage, plants have evolved multiple mechanisms for energy dissipation and photoprotection. To efficiently dissipate the excess excitation energy (EEE), the additional electron sinks, such as photorespiration, biosynthesis of phenolics and nitrate reduction are stimulated. Variegated leaves of Pelargonium zonale have been proven to be a suitable model system for examining ‘source–sink’ interactions within the same leaf, providing the same microenvironment conditions, unlike common root-shoot studies. The aim of our study was to investigate carbon and nitrogen reallocation between photosynthetically active (green leaf sectors) and photosynthetically inactive (white leaf sectors) under EEE pressure induced by low temperature in combination with high light intensity. Besides the amino acids and phenolics analyses, we monitored morphological and photosynthetic parameters of P. zonale leaves. Our results revealed higher content of free proteogenic amino acids in the white leaf sectors than in the green ones. Moreover, EEE triggered increased polyphenol synthesis, namely anthocyanins, already on the fourth day of the experiment. Also, the leaf fresh/dry weight (FW/ DW) ratio was significantly lower in plants exposed to EEE, indicating possible cell wall stiffening.Book of Abstracts: 4th International Conference on Plant Biology and 23rd SPPS Meeting, 6-8 October 2022, Belgrad