Photosynthèse, répartition des assimilats et rhizodéposition chez le maïs (Zea Mays L.) soumis à la compaction du sol

Abstract : The objective of this work was to investigate the effects of soil compaction on carbon assimilation, photosynthate partitioning, and morphology of corn plants during vegetative growth period up to tassel initiation. We were particularly interested in carbon input into the soil and soil microbial biomass. Corn plants were grown in culture pots containing compacted soil (bulk density of 1.45 g cm-3 ) or loose soil (bulk density of 1.30 g cm-3). Experiments were conducted in a growth chamber and lasted for 21 to 42 days. Carbon partitioning in the plant-soil system was evaluated using 14C pulse-labeling techniques. The increase in soil bulk density decreased carbon assimilation rate and total carbon fixation. Furthermore, soil compaction delayed leaf appearance rate decreasing therefore plant height, shoot dry weight, and leaf area. In addition, root biomass and root elongation were also inferior when plants were grown in compacted soil and root length appeared to be the most sensible parameter to high soil mechanical resistance. Simultaneously, a great increase in carbon input into the soil occurred to the detriment of root carbon. Soil microbial biomass increased considerably in compacted soil thanks to this increase in carbon substrates and to physical protection provided for soil microflora as a result of the reduced porosity in compacted soil. Three hypotheses were formulated to explain these results: 1- a decrease in soil or root water potential or a sink limitation induces a down-regulation of photosynthetic activity, 2- the increase in root diameter decreases soil mechanical resistance, and 3- the increase in carbon rhizodeposition alleviates the effects of mechanical constraint. The effects of soil compaction persisted with plant age although the difference between the two treatments decreased in terms of percentage.
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Ashraf Tubeileh. Photosynthèse, répartition des assimilats et rhizodéposition chez le maïs (Zea Mays L.) soumis à la compaction du sol. Sciences agricoles. Institut National Polytechnique de Lorraine, 2000. Français. ⟨NNT : 2000INPL088N⟩. ⟨tel-01749946⟩

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