Magnesium and phosphorus distributions in developing tartary buckwheat cotyledons / Razporeditev magnezija in fosforja v razvijajočih se kličnih listih tatarske ajde

Tartary buckwheat ( Fagopyrum tataricum (L.) Gaertn.) is a gluten-free pseudocereal with good mineral element composition of grain. In particular, Tartary buckwheat grains have greater magnesium (Mg) concentration than ce- real grains. In (pseudo)cereal grain, Mg is bound to phytic acid, a phosphorus (P)-rich compound responsible for poor availability of Mg in the diet. The aim of the study was to evaluate changes in cell-type specific distribution of Mg and P in cotyledons of Tartary buckwheat grain and in 5-day-old and 8-day-old sprouts. Low-energy-X-ray-fluorescence map- ping revealed considerable co-localisation of Mg and P in globoid-like structures in cotyledons. In the grain these globoid-like structures were numerous and appeared in mesophyll cells of the cotyledons. In 5-day-old sprouts less Mg-P co-localisation was seen in mesophyll cells. In 8-day-old sprouts co-localisation of Mg and P was less confined to globoid-like structures in the mesophyll cells indicating the degradation of these globoids and release of Mg, presumably for different metabolic processes that occur during seedling development. The extent to which Mg release from phytic acid in sprouts correlates with the bioavailability of Mg during digestion remains to be investigated. Keywords : Fagopyrum tataricum , X-ray fluorescence micro-spectroscopy, sprouts, phytic acid, germination Tatarska ajda ( Fagopyrum tataricum (L.) Gaertn.) je nepravo žito, ki ne vsebuje glutena in ima za prehrano ugodno mineralno sestavo. Zrnje tatarske ajde vsebuje na primer vec magnezija (Mg) kot zrna pravih žit. V zrnju pravih, kot nepravih žit, je Mg mocno vezan na fitinsko kislino, organsko spojino, ki je zgrajena iz velikega stevila atomov fosforja (P). Omenjena vezava je odgovorna za slabo topnost Mg in slabo biodostopnost Mg v prehrani. Namen studije je bil ovrednotiti spremembe v razporeditvi Mg in P v razvijajocih se klicnih listih tatarske ajde. Preucevali smo klicne liste v zrnu, v pet in osem dni starih kalicah tatarske ajde. S pomocjo nizko-energijske rentgensko fluorescencne mikrospektroskopije smo na celicnem nivoju v klicnih listih zrn potrdili mocno kolokalizacijo Mg in P v globoidnih strukturah. V klicnih listih pet dni starih kalic se je stopnja kolokalizacije zmanjsala in globoidne strukture so bile manj stevilne. Stopnja kolokalizacije v klicnih listih osem dni starih kalic se je se dodatno zmanjsala, kar je nakazovalo na razgradnjo kompleksov fitinske kisline in Mg, verjetno kot posledica metabolnih potreb kalice po Mg. Potrebne so nadaljnje raziskave, s katerimi bi ovrednotili povezavo med postopnim sproscanjem Mg s fitinske kisline v kalicah in biodostopnostjo Mg v prebavilih. Kljucne besede: Fagopyrum tataricum , rentgensko fluorescencna mikro-spektroskopija, kalice, fitinska kislina, kalitev