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Assimilation, Partitioning, and Nonstructural Carbohydrates in Sweet Compared with Grain Sorghum

1990; Wiley; Volume: 30; Issue: 5 Linguagem: Inglês

10.2135/cropsci1990.0011183x003000050030x

1435-0653

D. M. Vietor, F. R. Miller,

Plant responses to elevated CO2

Nonstructural carbohydrate concentrations in stems are greater for sweet than grain sorghums [ Sorghum bicolor (L.) Moench). Knowledge of plant characteristics associated with high nonstructural carbohydrates in sweet sorghum will aid efforts to increase nonstructural carbohydrates in grain sorghum stems. This study tested the hypothesis that variation of CO 2 assimilation rate, leaf area, branching at upper nodes, and partitioning of 14 C‐labeled assimilate to main stems are associated with variation of stem nonstructural carbohydrates. A sweet (Atlas ✕ Rio) and a grain (ATx623 ✕ RTx5388) hybrid, stages near and after physiological maturity, and defoliation and gibberellic acid (GA 3 ) treatments provided sources of variation for study. Concentrations of nonstructural carbohydrates in lower and upper stems of the sweet hybrid were 1.4 and 2.7 times higher, respectively, than for the grain hybrid, after physiological maturity. Variation in branching, including 14 C‐assimilate partitioning to branches, was not consistently associated with hybrid differences in stem nonstructural carbohydrates. Increased recovery (twofold) of 14 C‐assimilate in roots and labeled leaves corresponded with lower percentages of 14 C‐assimilate and lower concentrations of nonstructural carbohydrates in stems of the grain hybrid. Leaf areas and leaf CO 2 exchange rate were twice as great for the sweet hybrid. Although defoliation of the sweet hybrid minimized leaf area differences between hybrids, the sweet hybrid accumulated twice as much nonstructural carbohydrates in branches after physiological maturity. Greater potentials for CO 2 assimilation and for 14 C‐assimilate accumulation in mature stem tissue were associated with higher levels of stem nonstructural carbohydrates in the sweet compared with the grain hybrid.