Impact of three lateral root types identified in pearl millet on water uptake
Résumé
Pearl millet plays an important role for food security in arid regions.
Improving its root system toward increased water uptake
efficiency could improve pearl millet tolerance to drought and
lead to a significant production rise under water-limiting conditions.
The objective of this work was to provide an integrated
description of root system development at early stages and to
assess the consequences of these findings for water uptake. A
precise description of pearl millet root system development evidenced
large variability among lateral root growth profiles. To
further analyze this diversity, the growth rates of many lateral
roots were measured daily and a statistical model was designed
to classify these roots on the basis of their growth profiles. Three
categories of lateral roots were identified in this way: (i) roots
with high growth rate that could keep on growing after the end
of the experiment, (ii) roots with intermediate growth rates and
(iii) roots with low growth rates that quickly stop growing. The
different lateral root types were randomly distributed along the
primary root and there was no influence of root types on the
intervals between successive lateral roots. The proportions of
these different types were variable between plants of the same
genotype, suggesting that small environmental variations could
control these proportions. Water movements between soil and
roots is modeled with R-SWMS to assess (i) the benefits of the
three-type structuring, (ii) the relative contribution of each type
to water uptake and (iii) the impact of specific proportions on
global water uptake.
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