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Title: CARBOHYDRATE DISTRIBUTION IN STALKS AND EARS OF SWEET MAIZE WITH DIFFERENT ENDOSPERM GENOTYPES

Author
item Russo, Vincent
item Collins, Julie
item Perkins Veazie, Penelope
item Smith, T

Submitted to: Cereal Research Communications
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/3/2003
Publication Date: 4/20/2004
Citation: Russo, V.M., Collins, J.K., Perkins Veazie, P.M., Smith, T. 2004. Carbohydrate distribution in stalks and ears of sweet maize with different endosperm genotypes. Cereal Research Communications. 32(1):91-98.

Interpretive Summary: How sugars move through sweet corn (Zea mays L.) tissues to be deposited in kernels needs to be clarified. Tissues of the sweet corn cultivars 'Summer Flavor #72Y', 'Merit', and 'Supersweet Jubilee', which have the sugar enhanced, sugary 1, or shrunken2 endosperm types, respectively, were sampled at developmental stages from juvenile to fresh-market maturity for glucose, fructose and sucrose content. Fructose and glucose declined, but sucrose increased in stalks. In developing ears fructose and glucose increased. Sugars were generally unchanged in cobs. In kernels, fructose, glucose, and total carbohydrates (TCARB) decreased while sucrose, starch and water soluble polysaccharides (WSP) were unchanged in 'Summer Flavor #72Y'. In 'Merit', fructose and glucose decreased while sucrose, WSP and TCARB increased, and starch stayed the same. In 'Supersweet Jubilee' fructose decreased and glucose, starch, and WSP was unchanged, and sucrose and TCARB increased. Analysis suggests that patterns of sugar movement through tissues are different in the cultivars. Patterns of carbohydrate movement decreased in complexity in the order of 'Summer Flavor #72Y', 'Merit', 'Supersweet Jubilee'. Understanding how sugar levels in tissues change as plants develop should be helpful in predicting kernel sugar content in improved cultivars, and identify developmental stages, and tissues, which are important in distribution of sugars in sweet corn.

Technical Abstract: Sweet corn (Zea mays L.) kernels are carbohydrate sinks. Stalk tissues can be a sink or a source. Quantity of sugars present in sweet corn tissues, especially those other than kernels, are not well documented. Amounts of fructose, glucose, sucrose and their total in the 9th stalk internode (I9) from the 12-leaf stage (V12) to fresh-market maturity (R3) were determined in the 'Summer Flavor #72Y', 'Merit', and 'Supersweet Jubilee' sweet corn which have the sugar enhanced, sugary 1, or shrunken2 endosperm types, respectively. Developing ears (DE) were sampled at tassel emergence (VN) and silking (R1). Kernels and cob tissue were sampled at blister (R2) and R3 stages. Amounts of water soluble polysaccharides (WSP), starch, and total carbohydrates (TCARB; the added values for individual sugars, WSP, and starch) in kernels were determined at R2 and R3. Correlation analysis was performed on percentage of sugars at all developmental stages. In I9, from V12 to R3, fructose and glucose declined, but sucrose increased in al cultivars. In DE, fructose and glucose increased between VN and R1. In cobs sugars were generally unchanged in cultivars from R2 to R3. In kernels, fructose, glucose, total sugar and TCARB decreased while sucrose, starch and WSP were unchanged in 'Summer Flavor #72Y'; in 'Merit', fructose, glucose and total sugar decreased while sucrose, WSP and TCARB increased, and starch stayed the same; and in 'Supersweet Jubilee' fructose decreased, glucose, total sugar, starch, and WSP was unchanged, and sucrose and TCARB increased. Analysis suggests that patterns of sugar translocation through tissues are different in the cultivars. Patterns of carbohydrate movement decreased in complexity in the order of 'Summer Flavor #72Y', 'Merit', 'Supersweet Jubilee'.