Yellow deposits formation in roots is a part of tobacco plant phenotype under sulfur deficiency

Background and Purpose: It is known that plants respond to sulfur (S) deficit by adapting their physiology and development. Nowadays, scientists concentrate on the cellular level of such response, studying molecular processes, often treating visual phenotypes as fully explored and obvious. The goal of this study was to challenge such believes and find a new visual phenotype of plants during their response to S deficit. Materials and Methods: The macroscopic and microscopic observation of Nicotiana tabacump/ants grown under sulfur deficiency or control condition was conducted. Additionally, the absorbance spectrum of ethanol extracts from plant roots was measured. Results and Conclusions: In this study we showed that root color changes from colorless to yellow after transfer to S deficiency conditions. Microscopic observation of yellow roots showed that their color is a result of the yellowish deposits formation inside the root epidermis cells. Next experiments allowed to narrow down the list of chemicals responsible for the observed root phenotype to UV absorbing compounds. Our results, taken together with the data available in literature, pointed to the phenolic compounds as the most probable component of yellowish deposits responsible for change of root color during plant response to S deficiency. The physiological role of such accumulation is yet to be determined.