Sammendrag
Aim Root growth strategies may be critical for seeding
survival and establishment under dry conditions, but
these strategies and their plasticity are little known. We
aim to document the ability of young grass seedlings to
adjust their root system architecture, root morphology
and biomass allocation to roots to promote water uptake
and survival under progressive drought.
Methods Seedlings growing in columns filled with sand
and exposed to drought or well-watered controls were
repeatedly harvested for determination of biomass fractions, root length, −architecture and -morphology in a
greenhouse experiment. Allometric scaling exponents
and standardised major axis regression were used to
investigate allocation patterns.
Results Young seedlings were able to sustain leaf turgor
and functions during eight weeks of progressive drought
through phenotypic plasticity of the primary root system
producing deeper and simpler roots. Biomass allocation
to roots decreased or did not respond, and other components of root morphology showed only moderate
plasticity.
Conclusion Our results suggest that morphological and
architectural plasticity of the primary root system may
well be key features for dehydration avoidance and
survival in grass seedlings under moderate drought
when allocation of biomass to roots and development
of secondary roots are constrained.
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