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Croissance racinaire en verger de pêchers - Influence de la disponibilité en assimilats carbonés et des contraintes du sol

Abstract : Fruit tree production in Mediterranean climate needs water supply via irrigation, particularly during summer. To improve water use efficiency, it is necessary to better understand the water need of tree and to localize soil volumes colonized by roots. Root growth varies in time and space following endogenous factors, like carbohydrate availability, and exogenous factors like soil properties. These factors are affected by cultural practices and particularly by irrigation, soil compaction and thinning. Root growth dynamics is marked by two intensive root growth periods. The first period of intensive root growth occurs early in the season, in April-May, during the phase of stone hardening of fruit. Early in the season, carbohydrates demand at tree scale is high (leaves, fruits, shoots, roots are growing) and leads to an intense mobilization of starch reserve. Crop load affects root and fruit growth, and the deficit irrigation affects principally the aerial growth. The second period of intensive root growth occurs after the fruit harvest in July-August, when leaves and shoot stopped their growth. Competition for carbohydrates is reduced and starch contents rise, particularly in trees submitted to deficit irrigation. Starch accumulation traduces a higher sensibility of growth than photosynthesis under deficit irrigation. During intensive root growth periods, apical diameter and the length of apical unbranched zone are increased, and water soluble carbohydrates contents in root tips too. Root architectural parameters and water soluble carbohydrates contents are good indicators of root growth dynamics. Root distribution in orchard is variable and depends of soil properties. Roots of wellirrigated trees colonized especially soil volumes in the row (under drippers) until 1 m in depth. On the opposite, root of trees submitted to deficit irrigation colonized the first 50 cm in depth, both in the row and the inter-row. Root colonized soil volumes where soil mechanical resistance was the lowest, and these soil volumes are more reduced in deficit irrigation. Low soil mechanical resistance, with low bulk density and high water content, allows a higher root elongation and particularly for thick roots. On the opposite, fine roots have a higher elongation in strength soil than thick roots. The soil mechanical resistance leads to reduce the root system hierarchy; lateral roots were more branched
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  • HAL Id : tel-00518376, version 1
  • PRODINRA : 247282

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Carole Bécel. Croissance racinaire en verger de pêchers - Influence de la disponibilité en assimilats carbonés et des contraintes du sol. Sciences agricoles. Université d'Avignon, 2010. Français. ⟨NNT : 2010AVIG0627⟩. ⟨tel-00518376⟩

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