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Accueil du site → Doctorat → États-Unis → 1992 → Growth retardants promote drought resistance in corn (Zea mays L.)

Colorado State University (1992)

Growth retardants promote drought resistance in corn (Zea mays L.)

Kasele, Idumbo Nsongi

Titre : Growth retardants promote drought resistance in corn (Zea mays L.)

Auteur : Kasele, Idumbo Nsongi

Université de soutenance : Colorado State University

Grade : Doctor of Philosophy (PhD) 1992

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. 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$\sp-1$), and five ethephon treatments (no application and combinations of 0.56 and 0.84 kg a.i.ha$\sp-1$ with 0.28 kg a.i.ha$\sp-1$ applied at two growth stages). In 1990, the treatments were altered to include a factorial combination of four plant densities (24700, 37045, 49390, and 61735 plants ha$\sp-1$) and three ethephon rates (0.00, 0.28, and 0.56 kg ha$\sp-1$ a.i. applied at six-leaf growth stage) grown under rainfed conditions. Plant height, leaf area index, dry matter yield, cumulative evapotranspiration, grain yield and yield components were measured for the treatments. 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.

Mots clés : soil water, Ecology, Agronomy, Biological sciences, Botany

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Page publiée le 22 octobre 2015, mise à jour le 19 novembre 2018