STEM INFUSION OF FIELD-GROWN MAIZE

Field experiments were conducted in summer 1992 on the Central Experim ental Farm, Ottawa (45 degrees 22'N, 75 degrees 43'W) to determine whe ther a stem infusion technique developed for maize under controlled co nditions was applicable to field-grown maize and to evaluate whether p roviding sucrose in solution at silking via stem infusion altered plan t source-sink relationships sufficiently to increase kernel set. The h igher and more variable evaporative demand and more difficult installa tion under field conditions dictated modifications to the stem infusio n apparatus to prevent leakage and to facilitate assembly prior to fie ld set-up. A range of several field parameters were tested to identify conditions that would maximize infusion of sucrose solution: raising the syringe barrel height increased the volume of solution uptake; the largest amount of sucrose was taken up using a concentration of 150 g sucrose L(-1), and consecutive multiple infusions of the same plant i ncreased solution uptake. Solution uptake was found to be greatest in the first 24 h of infusion. Leaf soluble carbohydrate and starch conce ntrations and ear leaf photosynthesis were not changed by sucrose infu sion. Sucrose solution infused at silking appeared to increase kernel set in one of the experimental hybrids.