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Accueil du site → Doctorat → États-Unis → 1992 → Physiological and morphological traits associated with nitrogen uptake and use in Moroccan wheats at different moisture regimes

University of Nebraska - Lincoln (1992)

Physiological and morphological traits associated with nitrogen uptake and use in Moroccan wheats at different moisture regimes

Karrou Mohammed

Titre : Physiological and morphological traits associated with nitrogen uptake and use in Moroccan wheats at different moisture regimes

Auteur : Karrou Mohammed >

Université de soutenance : University of Nebraska - Lincoln

Grade : Doctor of Philosophy (PhD) 1997

Résumé
Nitrogen (N) fertilizer recommendations are among the crucial problems to be addressed for the erratic conditions of the arid and semi-arid areas of Morocco. One potential solution to this problem for wheat is the selection of cultivars with improved N use efficiency. However, to be more efficient, selection requires the understanding of the physiological and morphological mechanisms associated with N uptake and use under different soil moisture regimes. To reach this objective, studies were conducted with three bread wheat cultivars. Water regime differences were created by a line source irrigation system in the field, or by withholding water during stem elongation in the controlled environments. Data from the greenhouse and growth chamber studies showed that overall, Merchouch 8 had higher CO$\sb2$ assimilation efficiency (AEI) and CO$\sb2$ exchange rate (CER) and was more adapted to different soil N conditions than the other cultivars. Severe water stress masked the effect of N on dry matter production and shoot N content, and decreased N uptake and influx. The reduction of growth due to water stress was more important under high than low N. Plants that were water stressed during stem elongation increased their N influx during the period of recovery to a higher level than those not stressed. Under water stress, both high and low N tended to stimulate some stomatal closing. However, CER decreased only when N rate was increased.^ Field studies showed that grain and biomass yields were affected by water regime x N x cultivar interaction. Merchouch 8 was the most and Saada the least responsive to N rate increase. Nitrogen supply had a negative effect on nitrogen harvest index under the dry regime. The earliest cultivar, Merchouch 8 used more water, but had higher water use efficiency, and produced more grain and biomass when N was provided. Canopy temperature measurement was a better indicator of wheat performance than diffusive resistance. Nitrogen supply tended to increase dry matter production, leaf area index and root length per volume of soil. ^

Mots clés : Agronomy, water stress, Biological sciences, Botany

Présentation

Page publiée le 17 septembre 2010, mise à jour le 8 septembre 2017