Distribution of photosensitive fagopyrin in buckwheat flowers and its potential biological relevance.

Fagopyrum esculentum (Moench) is a valuable pseudo-cereal valued for its highly nutritious, gluten-free seeds. Despite being recognized as a 21st -century superfood, buckwheat remains non-competitive in seed yield compared to common cereals. Low productivity is mainly caused by abnormalities in female gametophyte development and frequent flower and embryo abortion. Buckwheat flowers accumulate high levels of phototoxic fagopyrin (FAG), whose physiological role remains unclear. FAG and its precursor (PFAG) are light-sensitive compounds with absorbance spectra in the green-yellow range (549-593 nm, peak at 590 nm), which makes their accumulation potentially responsive to light conditions. To address this, plants were cultivated under different light spectra, and the content of FAG and PFAG was analyzed in distinct floral organs (stamen, pistil, petal, and receptacle) using LC-MS, with their spatial distribution assessed by the MALDI-MS imaging. Pistil showed statistically the highest FAG and PFAG contents, while petals contained the lowest levels. A high density of FAG surrounding the ovary indicates a potential role in the reproductive part. Moreover, negative correlations were detected between flower production and FAG levels in the receptacles and pistils under specific light treatments. These results suggest that FAG may influence flower production and female gametophyte development, linking light environment to reproductive success in buckwheat.