Stem and Root Carbohydrate Dynamics of Two Cotton Cultivars Bred Fifty Years Apart
2002
Wells, Randall S.
Little is known concerning carbohydrate pools within the nonleaf and nonreproductive portions of the cotton (Gossypium hirsutum L.) plant. A 2-yr field study was conducted to ascertain both the concentration and total content of soluble carbohydrate and starch in upper stems, lower stems, vegetative branches, and roots of two cultivars released approximately 50 yr apart [Deltapine (DPL) 14 and 5690] from the same breeding program. In addition, yield, canopy photosynthesis, nodes above white flower, and white flowers per square meter were measured in the second year. Cultivar main effect was significant for soluble carbohydrate, total carbohydrate (soluble carbohydrate + starch), root dry weight, and total stem and root dry weight per plant. These differences are reflected by the generally greater dry weight and larger soluble carbohydrate concentration of DPL 5690 at 143 d after planting in 1994. Deltapine 5690 also exhibited larger late-season, integrated canopy photosynthesis in 1994, attributing to its larger soluble carbohydrate content. There was an initial increase in total stem and root carbohydrate per plant in each year followed by a decrease. Timing of the maxima and minima differed between years and between cultivars in 1994. Both the upper/lower stem carbohydrate ratios and the upper/lower stem starch ratios indicate declining upper-stem carbohydrate as flowering approached a hiatus and a shift in carbohydrate content towards the lower half of the stem. The data indicate that carbohydrate concentration and content per plant vary throughout the season; however, the cultivars exhibited little alteration in carbohydrate trends due to breeding efforts.
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