Influence of Leaf Grafting on Leaf Constituents and Senescence Characteristics of Burley and Flue‐Cured Tobacco

Productivity of flue‐cured tobacco (Nicotiana tabacumL.) is similar to that of burley tobacco in spite of the former's lower need for N fertilizer. The objective of this study was to utilize a leaf grafting technique to demonstrate the level of control of an individual leaf with regard to the unique characteristics of burley and flue‐cured tobacco cultivars. Leaves of burley cultivar ‘Ky 14’ were grafted onto shoots of flue‐cured cultivar ‘Speight G28’ (G28) and visa versa and compared to both grafted and nongrafted controls of a particular cultivar. Plants were grown in a greenhouse at two N fertility levels (648 or 144 mg N wk−1). Leaf grafting decreased leaf growth of both the burley and the flue‐cured cultivar compared to nongrafted controls, but relative cultivar differences were maintained. Compared to Ky 14, G28 leaves accumulated more dry weight, due primarily to greater starch accumulation, had higher chlorophyll concentration and, at low N fertility, maintained a higher carbon dioxide exchange rate (CER) and ribulose 1,5‐bisphosphate carboxylase/oxygenase (rubisco) concentration. Grafting a Ky 14 leaf onto a G28 stalk or a G28 leaf onto a Ky 14 stalk did not alter dry weight, starch, or N characteristics of the grafted leaf. Leaf senescence, however, as indicated by loss of chlorophyll, CER, and rubisco, was delayed for Ky 14 leaves grafted onto G28 stalks. For G28 leaves grafted to Ky 14 stalks, loss of chlorophyll was hastened, but declines in CER and rubisco were not altered. The results indicated that cultivar differences in dry weight and starch accumulation were controlled by biochemical or physical factors within an individual leaf, but that senescence characteristics of individual leaves could be influenced by the plant genotype.