Prevention of reproductive failure in maize plants at low water potentials by stem tissue infusion

Abstract

A delivery method for rapid external supply of dilute or concentrated doses of water soluble materials to maize plants was developed. The route of access is through a small cavity prepared in the stem which acts as an infusion port. A rubber septum serves as an adaptor to both seal the site and to provide a means of liquid access. Fluids can be delivered to the stem at 2-10 ml h^-1 per infusion site. This stem infusion technique was utilized in the study of maize reproductive physiology. First, stem infusion of a liquid tissue culture medium was used to replace the estimated daily losses in dry weight gain of reproductive maize plants rendered temporarily incapable of photosynthesis during a water deficit. Second, the plant hormone abscisic acid was infused into the stems of well-watered maize plants to study the effects of reduced photosynthesis on maize reproductive growth without the complication of low water availability. Stem infusion of liquid tissue culture medium was highly effective in preventing reproductive failure induced in maize plants by low water potential (low ψ[w]) at anthesis. This was done experimentally, without rehydrating the plant, by the infusion of a small volume of the culture medium. Dehydrated plants which received infusion of a similar volume of water or which were not infused experienced nearly complete reproductive failure. Following rehydration, all plants exposed to low ψ[w] during anthesis recovered photosynthesis, but only those infused with the medium during low ψ[w] continued kernel development to maturity. Final grain yields of some of the medium-infused plants approached control yields. Subsequent experiments indicated that sucrose was required, but plant growth regulators were not required for an effective medium. These experiments identify assimilate supply and not low plant ψ[w] per se as a limiting factor in maize reproductive failure and suggest that improvement in drought tolerance may be achieved by changes in the assimilate storage patterns and/or the phenology of maize plants...