Composition of seed soluble carbohydrates and ultrastructural diversity of testa in lupins from the mediterranean region

Abstract

This article present a comparison of soluble sugar levels in seeds of Lupinus atlanticus, Lupinus cosentinii, Lupinus palaestinus and Lupinus pilosus, Lupinus hispanicus subsp. hispanicus and Lupinus luteus of Juno variety. Considering that sugars are accumulated in embryos, only the embryonic tissues were used for biochemical analyses. Additionally, the share of testa and embryo in seed tissues was evaluated. The seed-coat thickness was measured using scanning electron microscopy. The seed coat had the largest share in seeds of Lupinus pilosus and Lupinus palaestinus, and the least share in seeds of Lupinus hispanicus subsp. hispanicus and Lupinus luteus of Juno variety. In the seed of Lupinus pilosus the thickness of the seed coat was 1100 µm, while in Lupinus luteus it was 300 µm. The analysed Lupinus seeds accumulated from 73 mg/g d.m. (dry matter of seed embryo) to 155 mg of soluble sugars/g d.m. The highest quantity of oligosaccharides of the raffinose series was found in seeds of Lupinus luteus, while the lowest amount in seed of Lupinus palaestinus. Galactosyl cyclitols appeared in largest amount in seeds of Lupinus palaestinus and Lupinus pilosus, appropriately 41.93 and 33.75 mg/g dm. The lowest amount of galactosyl cyclitols appeared in Lupinus atlanticus, Lupinus cosentinii and Lupinus hispanicus.