Effects of Stem‐injected Sucrose on Grain Production, Dry Matter Distribution, and Chlorophyll Fluorescence of Field‐grown Corn Plants

Abstract

AbstractA field experiment was conducted to evaluate the effect of long‐term exogenous sucrose supply on aspects of corn plant physiology and development during the grain filling period. Concentrated sucrose solution was supplied to corn (Zea mays L.) stems by an injection technique. This injection technique delivered pressurized solutions through syringe needles sealed to the stem with latex. The pressure was applied to the syringe plunger with ceramic construction bricks. Solutions containing sucrose at 0, 150, and 300 g L−1 were injected over a 32 day period encompassing the duration of the active grain filling period. The primary ears of plants injected with sucrose produced approximately 50% more kernels and 30% more grain weight than those injected with distilled water. The injected internode was also considerably heavier (56%) for plants receiving 300 g sucrose L−1 than plants receiving distilled water. For all measured variables, plants injected with distilled water were either not different from or had larger values than the non‐injected controls. After one week sucrose injection caused photo‐synthetic inhibition (as measured by chlorophyll fluorescence) in the leaf just above the ear and the ear leaf, and this was more severe for plants receiving 300 g sucrose L−1 than for those receiving 150 g sucrose L−1. For sucrose injected plants, the increased size of the primary ear was concomitant with a large decrease in grain production by the secondary ear and an overall decrease in per plant grain production. These results suggest that the mechanisms for signalling between sinks (the primary and secondary ears) and the primary sink and the source (leaves) are different.