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The Effect of DNBP on the Accumulation of ¹⁴C-Sucrose and the Transport of ¹⁴C-Assimilates in Corn¹

Subtoxic rates of DNBP (2-sec-butyl-4, 6-dinitrophenol) sprayed on corn (Zea mays L.) have been reported to stimulate dry matter accumulation in the grain in some situations. The purpose of this work was to evaluate the short-term effect of the application of DNBP on the accumulation of sucrose and the translocation of ¹⁴C-assimilates.

Premerge 3 (Dow Chemical Company) as a source of DNBP was sprayed on the 4- to 5-week old leaves of green-house-grown corn, 16 to 24 hours prior to leaf disc sampling or ¹⁴CO₂ labeling. Leaf discs were also floated on DNBP and DNP prior to ¹⁴C-sucrose accumulation studies.

The accumulation of ¹⁴C from a 10 mM ¹⁴C-sucrose solution in discs from untreated leaves was significantly greater than that of discs from leaves sprayed with DNBP or floated on ¹⁴C-sucrose containing 0.7 mM DNBP or DNP. Efflux of ¹⁴C from the treated leaf discs indicated a pool of ¹⁴C easily leached from the discs. ¹⁴C retained was five times greater in untreated leaf discs.

The transport of ¹⁴C-assimilates in DNBP treated and untreated leaves suggested an inhibition of long distant transport with 18.7% of the assimilated ¹⁴C transported in 30 min in treated leaves and 29.5% of the assimilated ¹⁴C translocated in untreated leaf discs. A significantly greater percentage of ¹⁴C was recovered in the sink of untreated plants than was found in the sink of DNBP sprayed plants.

These experiments support the hypothesis that DNBP acts as an inhibitor of ¹⁴C-sucrose accumulation and the movement of ~C-assimilates from the source leaf in corn.

Key Words: Translocation • Sucrose uptake • Zea mays • DNP • Sucrose accumulation

² Assistant professor, Dep. de Fitotecnia, Centro de Ciencias Agrarias, Universidade Federal de Ceara, Fortaleza, Ceara, Brazil.

³ Assistant professor and professor, Agonomy Dep., Purdue Univ. West Lafayette, IN 47907.

⁴ Graduate assistant, Agronomy Dep., Plant Science Building, Univ. of Georgia, Athens, GA 30601.

Received for publication October 25, 1979.