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Integration of plant and soil knowledge

Apr 05, 2018

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    Integrating soil and plant knowledgeat different scales to betterunderstand the dynamics

    of water in SPAC

    Nottingham, 11 September 2008

    G. LOBET, L. PAGES, F. CHAUMONT,M. JAVAUX & X. DRAYE

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    Plan

    Context

    Material and methods

    Results

    Discussions

    Conclusions

    1

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    Context

    2Context Experience Results Discussions Conclusions

    Context Material and methods Results Discussions Conclusions

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    Water movement in plants

    3Context Experience Results Discussions Conclusions

    Several resistances:

    - in the stomata- along the xylem vessels- uptake by the roots

    Soil-Plant-AtmosphereContinuum

    Water potentialgradient

    Water movement

    Context Material and methods Results Discussions Conclusions

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    Aquaporins increasemembrane permeability

    - increase the water flow ratethrough the membranes

    -ZmPIP2:5 mainly present inendoderm and exoderm of maize

    roots

    Aquaporins

    5

    To test the quantitative contribution ofZmPIP2:5 at the root system level

    From: Hachez et al., 2006

    Context Material and methods Results Discussions Conclusions

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    Material and methods

    6Context Material and methods Results Discussions

    Context Material and methods Results Discussions Conclusions

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    Material

    Three tools were used:- transgenic plants deficient inZmPIP2:5- rhizotrons- light transmission imaging

    To get picture of the water

    distribution inside de rhizotronsat a low time scale

    7Context Material and methods Results Discussions ConclusionsContext Material and methods Results Discussions Conclusions

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    Methods

    Six rhizotrons- 3 Transgenic + 3 Wild-Type

    When plants are 30 days old:- substrate at the field capacity- water supply is stopped- light transmission imaging every 2 hours during 2 1/2 days.

    8Context Experience Results Discussions ConclusionsContext Material and methods Results Discussions Conclusions

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    Results

    9Context Experience Results Discussions ConclusionsContext Material and methods Results Discussions Conclusions

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    Growth parameters

    Shoots:- similar growth rate for all the plants

    Roots:- two groups:

    10Context Experience Results Discussions Conclusions

    Deep Superficial p-value

    Depth (cm) 75.0 + 8.66 48.3 + 7.64 0.016 *

    Growth rate(mm/day)

    19.21 + 7.65 11.53 + 4.15 0.008 **

    intrinsic variability

    of the growth rate

    Trangenics Wild-types p-value

    Depth (cm) 61.7 16.1 60.0 17.3 0.909

    Growth rate(cm/day)

    16.7 6.8 11.6 4.9 0.352

    Context Material and methods Results Discussions Conclusions

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    Transpiration

    11Context Experience Results Discussions Conclusions

    During the day- effect of stomatal regulation

    Across days- water less available- roots less efficient

    Context Material and methods Results Discussions Conclusions

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    Aquaporins

    Western Blot at the end of the experiment:- no differences between Transgenics and Wild-Type

    Morphological differences

    12Context Experience Results Discussions Conclusions

    Variation of the expression of the silencing?- Influence of the temperature

    Trangenics Wild-types p-value

    root:shoot 0.99 + 0.035 0.86 + 0.062 0.032 *

    % primaryroots

    21.59 + 1.90 14.18 + 2.95 0.022 *

    Transgenics produce:

    - more roots- more primary roots

    Context Material and methods Results Discussions Conclusions

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    Localised

    Rapid apparition of a dry zoneThe uptake region moves down quickly

    - effect of the substrate and root density (?)

    Uptake

    13Context Experience Results Discussions ConclusionsContext Material and methods Results Discussions Conclusions

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    Uptake pictures

    Superficial Deep

    Identical behaviours for the differenttype of root systems

    14Context Experience Results Discussions ConclusionsContext Material and methods Results Discussions Conclusions

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    Discussions

    15Context Experience Results Discussions ConclusionsContext Material and methods Results Discussions Conclusions

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    Hypotheses on the influenceof the lack of aquaporins

    On the development- roots less efficient if lacking AQP- increase of the root surface in order to balance the decrease

    in efficiency:

    - creation of new roots- increase in the growing rate of the existing roots (?)-

    Functional equilibria (Brouwer 1963) Equilibrium between supply and demand

    16Context Experience Results Discussions ConclusionsContext Material and methods Results Discussions Conclusions

    increase of branchingincrease of branching

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    In case of water stress- roots in the dry zone produce ABA- stomatal closure and decrease of transpiration

    If uptake localised- faster response of the roots

    Negative feed-back

    Prevent a drying of the rhizosphere

    Same dynamics observed in Partial RootZone Drying experiments (PRZD)

    Hypotheses on transpirationand water uptake

    17Context Experience Results Discussions ConclusionsContext Material and methods Results Discussions Conclusions

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    Conclusions

    18Context Experience Results Discussions ConclusionsContext Material and methods Results Discussions Conclusions

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    Conclusions

    The lack of aquaporins may have an influence on thedevelopmental processes (to be confirmed)

    The localised dynamics of the water uptake

    induces a tight regulation of the global uptake behaviour

    Light transmission imaging allows theobservation of the water uptake in situ and without heavy

    equipment

    Functional-structural plant modelling could bea useful tool for the understanding of the water dynamics

    in plant

    19Context Experience Results Discussions ConclusionsContext Material and methods Results Discussions Conclusions

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    Acknowledgements

    UCL:

    Xavier DrayeMathieu JavauxFranois Chaumont

    20Context Experience Results Discussions ConclusionsContext Material and methods Results Discussions Conclusions

    INRA, Avignon:

    Loc PagsClaude Doussan

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    Thanks for your attention