| Reduction in early season vegetative growth and water use of corn with growth retardants (GR) can potentially increase available soil water during reproductive stages and increase grain yield under drought stress.;In the greenhouse, both GR treatments reduced leaf expansion, but increased specific leaf weight, stomatal density, soluble protein, and chlorophyll content. Stomatal conductance, carbon exchange rates, transpiration, and water use efficiency at single leaf basis were higher in treated plants. Ethephon application reduced plant height and leaf area index by 10 to 30% and therefore the early season evapotranspiration. Ethephon treatments either had no effect or reduced yields in 1989 under all irrigation and plant density levels, because of a lack of significant drought stress. However, when drought conditions existed in 1990, ethephon application decreased yields at low plant densities and increased yields with a maximum of 37% at high plant densities. Thus, GR treatments would appear to have the potential for improving drought resistance in corn.;Corn plants were treated with a seed-applied gibberellin biosynthesis inhibitor (GBI) and a foliar-applied (ethephon) GR and grown under greenhouse conditions, receiving optimal water and nutrients. Leaf area and weight, stomatal density and size, and leaf chlorophyll and soluble protein content were determined at the six-leaf growth stage. Leaf gas exchange characteristics were determined on 5th leaf using photosynthesis measuring system. Field experiments were conducted during the 1989 and 1990 growing seasons to determine the impact of ethephon application on vegetative growth, water use, and grain yield of corn grown under semiarid conditions in eastern Colorado. The 1989 experiment consisted of a factorial combination of two irrigation levels (limited and full), two plant densities (53333 and 80000 plants ha... |
