Stem Infusion of Maize Plants

A delivery method was developed for rapid exogenous supply of dilute or concentrated doses of water‐soluble materials to maize ( Zea mays L.) plants. The point of access was through a small cavity, prepared in the stem, which acted as an infusion port. A rubber serum bottle stopper with a septum served as an adapter both to seal the opening and to provide a means of liquid access. Conventional hypodermic needles were used to transport the liquid from an external reservoir across the septum of the stopper. Liquids were gravity‐fed under pressure heads ranging from 0 to 100 cm of water. During daylight hours, well‐watered plants could be infused with concentrated solutions such as liquid tissue culture media at 2 to 3 mL h −1 per infusion site. Water or dilute solutions could be infused at 5 to 10 mL h‐ −1 per infusion site. Multiple infusion sites were possible, thereby increasing the total rate of fluid infusion per plant. Infusions by this technique were used to provide physiologically significant quantities of nutritional or regulatory substances to maize plants. For example, a daily increment of ≈5 g dry weight of culture medium per plant, a quantity equivalent to the dry matter produced daily by photosynthesis, could be externally provided by the infusion ≈30 mL d −1 plant −1 . This allowed all the nutritional requirements of the plants to be supplied externally in a modest volume of solution. Infusion of 10 −4 M (±)‐abscisic acid also could be used to induce stomatal closure and temporarily reduce photosynthesis. Various applications of this technique to maize and other species may be possible.