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Root System Genotype and Nitrogen Fertility Effects on Physiological Differences between Burley and Flue-Cured Tobacco. II. Whole Plant¹

Flue-cured tobacco (Nicotiana tabacum L.) cultivars produce similar leaf yields compared to hurley tobacco cultivars despite requiring approximately four times less N fertilizer. This study is the second part of an experiment to characterize physiological differences between representative burley and flue-cured cultivars and to determine the influence of the root system on shoot physiology. Control and reciprocally grafted plants of burley ‘Ky 14’ and flue-cured ‘Speight G28’ (G28) were grown in soil pots [Maury silt loam (Typic Paleudalfs)] at two levels of N fertilization (580 or 230 mg N week"1)- Plants were sampled and divided into laminae, midveins, stalk, and roots from 10 days before to 30 days after topping. Dry weight distribution for the cultivars was similar for all plant parts except laminae. G28 accumulated significantly more lamina dry weight than Ky 14, although leaf area and leaf number were similar for both genotypes. Cultivar differences in lamina dry weight occurred even though lamina and stalk N contents were similar, within an N level. Thus, G28 produced more lamina dry weight based on either units of N fertilizer added or lamina N accumulated. Laminae dry weight differences were explained in large part by higher starch concentration for G28 than Ky 14. Laminae free sugar concentration was low and similar for all treatments. These data inferred that starch metabolism or storage capability was dissimilar for the two tobacco types. The genotype of the root system did not influence any parameter measured for shoots and, thus, differences between cultivars may be expressed at the level of the leaf lamina cell.

Key Words: Yb genes • Nitrogen efficiency • Nicotiana tabacum L. • Senescence • Partitioning

² Plant physiologist, USDA-ARS; agronomist, USDA-ARS; and professor of agronomy, Univ. of Kentucky, Lexington, KY 40546.

Received for publication February 5, 1987.