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

Abstract

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 več magnezija (Mg) kot zrna pravih žit. V zrnju pravih, kot nepravih žit, je Mg močno vezan na fitinsko kislino, organsko spojino, ki je zgrajena iz velikega števila atomov fosforja (P). Omenjena vezava je odgovorna za slabo topnost Mg in slabo biodostopnost Mg v prehrani. Namen študije je bil ovrednotiti spremembe v razporeditvi Mg in P v razvijajočih se kličnih listih tatarske ajde. Preučevali smo klične liste v zrnu, v pet in osem dni starih kalicah tatarske ajde. S pomočjo nizko-energijske rentgensko fluorescenčne mikrospektroskopije smo na celičnem nivoju v kličnih listih zrn potrdili močno kolokalizacijo Mg in P v globoidnih strukturah. V kličnih listih pet dni starih kalic se je stopnja kolokalizacije zmanjšala in globoidne strukture so bile manj številne. Stopnja kolokalizacije v kličnih listih osem dni starih kalic se je še dodatno zmanjšala, 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 sproščanjem Mg s fitinske kisline v kalicah in biodostopnostjo Mg v prebavilih.

Ključne besede: Fagopyrum tataricum, rentgensko fluorescenčna mikro-spektroskopija, kalice, fitinska kislina, kalitev