Nitrogen distribution within a sympodial branch of cotton
1992
Zhu, B. | Oosterhuis, D.M.
Although nitrogen (N) partitioning within the cotton (Gossypium hirsutum L.) plant has been documented, little is known about the distribution within a sympodial branch in relation to the development of individual bolls. Field studies were conducted on a Captina silt loam (Typic Fragiudults) to investigate the N distribution within a representative sympodial branch at main-stem node 10. The dry matter, percentage N and total N were determined at 7-day intervals during branch development for individual leaves, petioles, bolls, and the branch. The dry weight of the main-stem leaf, and the first three sympodial leaves along the branch peaked at 21, 28, 35, and 42 days, respectively, which coincided with the time of maximum total-N content. Peak N content for the main-stem leaf was 63 mg, and declined progressively with 60% of the total N exported within 42 days. However, individual sympodial leaves exhibited only a slight decrease in total-N content despite the increasing N requirement of the subtended bolls. The majority of the N accumulated in the bolls, while at the same time the N content of the leaves decreased, and the N content of the petioles and branches remained somewhat constant. The N concentration on a dry matter basis differed among various plant organs and tended to decline in both vegetative and reproductive organs as the season progressed. The leaves were the primary N sinks prior to anthesis, and thereafter the N sink was gradually shifted to the developing bolls. The N requirement of a developing boll may not be supplied solely via the subtending leaf and imports from additional sources may be required.
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