title: Assessment of an apparent relationship between availability of soluble carbohydrates and reduced nitrogen during floral initiation in tobacco.
abstract: Daily relative accumulation rate of soluble carbohydrates (RARS) and reduced nitrogen (RARN) in the shoot, as estimates of source strength, were compared with daily relative growth rates (RGR) of the shoot, as an estimate of sink demand, during floral transformation in apical meristems of tobacco (Nicotiana tabacum 'NC 2326') grown at day/night temperatures of 18/14, 22/18, 26/22, 30/26, and 34/30 C.  Source strength was assumed to exceed sink demand for either carbohydrates or nitrogen when the ratio of RARS/RGR or RARN/RGR was greater than unity, and sink demand was assumed to exceed source strength when the ratio was less than unity.  Time of floral initiation, which was delayed up to 21 days with increases in temperature over the experimental range, was associated with intervals in which source strength of either carbohydrate or nitrogen exceeded sink demand, while sink demand for the other exceeded source strength.  Floral initiation was not observed during intervals in which source strengths of both carbohydrates and nitrogen were greater than or less than sink demand.  These results indicate that floral initiation is responsive to an imbalance in the relative availabilities of carbohydrate and nitrogen.
authors.affiliation: Department of Soil Science, North Carolina State University, Raleigh 27695, USA.
authors.forename: C D
authors.initials: CD
authors.lastname: Raper
authors.forename: J F
authors.initials: JF
authors.lastname: Thomas
authors.forename: L
authors.initials: L
authors.lastname: Tolley-Henry
authors.forename: J W
authors.initials: JW
authors.lastname: Rideout
mesh_terms: D050260:Carbohydrate Metabolism; D018519:Meristem / Q000254:growth & development* / Q000378:metabolism; D009584:Nitrogen / Q000378:metabolism*; D018520:Plant Shoots / Q000254:growth & development* / Q000378:metabolism; D010947:Plants, Toxic; D013696:Temperature; D014026:Nicotiana / Q000254:growth & development / Q000378:metabolism
chemical_list: D009584:Nitrogen