Nonstructural Carbohydrates in Axillary Branches and Main Stem of Senescent and Nonsenescent Sorghum Types
1990
Vietor, D. M. | Miller, F. R. | Cralle, H. T.
Although the concentration of nonstructural carbohydrates in main stems has been compared between senescent and nonsenescent types of sorghum [Sorghum bicolor (L.) Moench], nonstructural carbohydrates in axillary branches at upper nodes have not been compared between senescence types. The objective of this study was to test the hypothesis that nonsenescent hybrids of semidwarf sorghum accumulate more nonstructural carbohydrates in branches and in the main stem than senescent hybrids after black layer. Plants were labeled (exposed to ¹⁴CO₂) 14 d before, at, and 14 d after black layer formation under field conditions. Nonstructural carbohydrates in branches and in lower and upper portions of the main stem were sampled 5 or 7 d after labeling. Comparisons between hybrids 14 d after black layer supported the hypothesis. The content of nonstructoral carbohydrates in branches increased twofold more for nonsenescent than for senescent plants between stages of labeling at and 14 d after black layer. The concentration and content of nonstructural carbohydrates in main stems of senescent plants declined 40% or more during the same period. Branches comprised 84 to 100% of the increase in content of nonstructural carbohydrates even though concentrations and ¹⁴C-photosynthate recoveries in the nonstructural fraction of branches declined after black layer. Nonstructural carbohydrates in branches at upper nodes need to be monitored in addition to those in main stems for comparisons involving the senescence types from this study. Contribution of Texas Agric. Exp. Stn., Technical Article no. 24349. Partially supported by Center for Energy and Mineral Resources, Texas A&M Univ.
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