Changes of carbohydrate composition of sweet maize (Zea mays L. Saccharata) grain during endosperm development

Abstract

Sweet corn is consumed as human food in the milk stage of grain development when grain is tender, soft and sweet. Sucrose, a dominant sugar at this stage of the endosperm development, causes sweetness of grain. The changes of grain carbohydrate composition of two genotypes (ZPSC 311 su and ZPSC 450 su) were monitored over stages of maturity (10, 15, 20, 23 and 28 days after pollination). This composition was determined by high pressure chromatography on the column with chemically bound stationary phase, type NH2 and polar mobile phase of acetonitrile-water. Carbohydrate composition of grain changed during the endosperm development in a way that the percentage share of fructose and glucose decreased, while the share of sucrose increased. The maximum value of a sucrose content on the 25th day after pollination amounted to 77.00% and 89.81% in ZPSC 450 su and 78.38% and 77.92% in ZPSC 311 su, in 1999 and 2000, respectively. Thereafter opposite changes occurred. Significant differences (of glucose, fructose) in the share of certain sugars over developmental stages in, were determined. A strong rank correlation between contents of glucose and fructose was detected indicating that the increased glucose content resulted in the increased fructose content and vice versa. Negative values for rank correlation was determined between contents of sucrose and glucose and contents of sucrose and fructose indicating that the increase of the sucrose content leads to the decrease of glucose and fructose contents and vice versa.

Kukuruz šećerac se upotrebljava za ishranu ljudi u mlečnoj fazi razvoja zrna kada je ono nežno, sočno i slatko. U toj fazi dominantan šećer u endospermu je saharoza koja daje slatkoću zrnu. U ovom radu praćene su promene ugljenohidratnog sastava zrna dva genotipa kukuruza šećerca (ZPSC 311 su i ZPSC 450 su) po fazama zrenja (10, 15, 20, 23 i 28 dana posle oplodnje). Ugljenohidratni sastav zrna određivan je metodom visokopritisne hromatografije na koloni sa hemijski vezanom stacioniranom fazom tipa NH2 i polarnom mobilnom fazom acetonitril-voda. Dobijeni rezultati pokazuju da se ugljenohidratni sastav zrna menjao tokom procesa razvoja endosperma, tako što se smanjivao udeo fruktoze i glukoze, a istovremeno povećavao udeo saharoze. Maksimalna vrednost sadržaja saharoze utvrđena je u fazi 25 dana posle oplodnje, 77,00% i 89,81% za ZPSC 450 su i 78,38% i 77,92% za ZPSC 311 su, tokom 1999. i 2000. godine. Nakon toga odvijale su se suprotne promene. Utvrđene su statistički značajne razlike u udelu pojedinih šećera po fazama zrenja, odnosno u zavisnosti od broja dana od oplodnje. Utvrđena je jaka korelativna veza između sadržaja glukoze i fruktoze, što ukazuje na to da se povećanjem sadržaja glukoze povećava i sadržaj fruktoze i obrnuto. Negativne vrednosti korelacije ranga nađene su između sadržaja saharoze i glukoze i sadržaja saharoze i fruktoze, što znači da se povećanjem sadržaja saharoze smanjuje sadržaj glukoze i fruktoze, i obrnuto.