Yield maintenance under drought: expansive growth and hydraulics also matter in reproductive organs
Résumé
Yield maintenance under drought in maize (Zea mays) is associated
with flowering synchrony which requires the rapid extension
of styles and stigma (silks) to be accessible for pollen. We
have shown that the control of grain set under moderate water
deficits similar to those in the field result from a developmental
process linked to the timing of silk growth, in opposition to the
common view that abortion is linked to the sugar metabolism
in ovaries. A switch to abortion occurs 2-3 days after first silk
emergence in water-stressed plants, when silk growth stops simultaneously
for all ovary cohorts, and explains abortion rates in
different treatments, genotypes and positions on the ear. Analyses
of transcripts and metabolites indicate that the first molecular
events occur in silks rather than in ovaries, and involve genes
affecting expansive growth rather than sugar metabolism. Sugar
availability is preserved in ovaries until the switch to abortion,
and the disruption of carbon metabolism only occurs afterwards.
Hence, changes in metabolite contents, transcript amounts and
enzyme activities involved in ovary sugar metabolism would be
a consequence rather than a cause of the beginning of ovary
abortion. Patterns of silk growth responses to environment share
common features with those of leaf growth, with both kinetic
and genetic evidences. These findings have large consequences
for breeding drought tolerant maize and for modelling grain
yields under drought. Oury et al (2016) Plant Physiology171: 986-
996 and 171: 997-1008
Turc et al (2016) New Phytologist 212: 377–388
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