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

Abstract

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 14C‐assimilates from the source leaf in corn.