Abstract
Pearl millet plays an important role for food security in arid regions.Improving its root system toward increased water uptakeefficiency could improve pearl millet tolerance to drought andlead to a significant production rise under water-limiting conditions.The objective of this work was to provide an integrateddescription of root system development at early stages and toassess the consequences of these findings for water uptake. Aprecise description of pearl millet root system development evidencedlarge variability among lateral root growth profiles. Tofurther analyze this diversity, the growth rates of many lateralroots were measured daily and a statistical model was designedto classify these roots on the basis of their growth profiles. Threecategories of lateral roots were identified in this way: (i) rootswith high growth rate that could keep on growing after the endof the experiment, (ii) roots with intermediate growth rates and(iii) roots with low growth rates that quickly stop growing. Thedifferent lateral root types were randomly distributed along theprimary root and there was no influence of root types on theintervals between successive lateral roots. The proportions ofthese different types were variable between plants of the samegenotype, suggesting that small environmental variations couldcontrol these proportions. Water movements between soil androots is modeled with R-SWMS to assess (i) the benefits of thethree-type structuring, (ii) the relative contribution of each typeto water uptake and (iii) the impact of specific proportions onglobal water uptake.