Root responses of seven perennial forage species to severe drought

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Root responses of seven perennial forage species to

severe drought

Marine Zwicke, A Bertrand-Morvan, Marie-Pascale Prud’Homme, Florence

Volaire, Catherine Cochard

To cite this version:

Marine Zwicke, A Bertrand-Morvan, Marie-Pascale Prud’Homme, Florence Volaire, Catherine

Cochard. Root responses of seven perennial forage species to severe drought. 8th Symposium of the

International Society of Root Research, Jun 2012, Dundee, United Kingdom. 2012. �hal-02804703�

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Perennial forage species

Dactylis glomerata Dg

Festuca arundinacea Fa

Dactylis glomerata cv Medly Md

Poa pratensis Pp Poa trivialis Pt Trisetum flavescens Tf Taraxacum officinalis To A L I M E N T A T I O N A G R I C U L T U R E E N V I R O N N E M E N T INRA – Centre de Clermont-Ferrand - Theix

UR874 Grassland Ecosystem Research 63100• Clermont Ferrand • France www.clermont.inra.fr/urep

Root responses of seven perennial forage species

to severe drought

Materials & Methods

Introduction

Future climate scenarios suggest an increase in intensity and frequency of severe droughts. Maintaining grassland services depends on plant community resistance. When total leaf senescence is reached, basal meristems are known to be survival organs, by accumulating carbohydrates, which play important roles for osmotic adjustment (sucrose especially) and available carbon for re-growth ability (fructans). Fructans with high degree of polymerization (HDP > 5) could prevent cell damages (Vereyken et al. 2003). We would like to know if roots may also survive under severe soil drought. First, we aimed to compare the response of basal meristems and root apices during severe drought in order to determine the role of roots in resistance and survival strategiesof seven forage species.

Conclusions

Fructans were the major components of WSC although their concentration was stable during drought but increased in Dactylis glomerata of Mediterranean origin (Md). Fructansand sucrose concentrations were higher in basalmeristems, probably enhancing their regrowth capacity. In parallel, drought induced changes in carbohydrates allocation in roots and root apices where the sucrose concentration increased, possiblyby contributingto osmotic adjustment, whereas fructansconcentration decreased. However, we found positive relationships between the concentration of highly polymerized fructans in roots and their membrane stability confirming previous results in basal leaf meristem (Volaire et al 1998, Amiard et al 2003). These results show that carbohydrate accumulation before the end of leaf growth are determinant for roots survival during and after severe drought. Roots measurements Water Soluble Carbohydrates (WSC) contents Membrane stability NON MONTRE Others : Roots depth and biomass , TTC coloration

Above-ground compartment during the experiment

Carbohydrates content in meristems and roots

Zwicke M., Bertrand-Morvan A., Prud’homme M-P., Volaire F., Picon-Cochard C

Root Apices Roots

Basal Leaf Meristems

F ru c ta n s c o n te n t (m g /g D M ) Md Tf Pp Fa Dg To Pt Summer leaf senescence Survival 2 weeks after rehydration Recovery at spring 2012

Days after last watering0 20 40 60 80

0 50 100 150 200 250 300 Control at rehydration ns ns

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Dg Fa Md Pp Pt Tf To S u c ro s e c o n te n t (m g /g D M )

0 20 40 60 80 100 Control at rehydration ns ns ns ns Acknowledgments: Feder Région Auvergne Méta-programme ACCAF Climagie

Specieswere sown in PVC tubes (depth = 150 cm; d =10 cm), in granitic soil at the end of September 2010. During winter, tubes were kept outside in soil for plant vernalization. Experiment started in March 2011: each culture was irrigatedat field capacity (23%). In

July, precipitations were reduced and thereafterstopped to induce severe drought during 50 days. At the end of August, tubes were rehydrated to measure population survival and recovery. Control tubes were

maintained at field capacity during all the experiment. Tubes Sampling 0 18 50 50 Before drought

End of leaf growth

Before rehydration Control tubes at

rehydration

Days after last watering D R O U G H T Mar.2011 Jul.2011 Aug.2011 Rehydration Sept.2011

Recovery

Survival

Irrigation at field capacity

Fructans are the main WSC in

roots. Although WSC contents

depended on species, sucrose and

fructansdecreasedby drought. Pp,

Tf and Md showed highest sucrose

contents in roots at the end of

drought, whereas Fa, Dg and Pt showed lowest fructans content.

As other organs, fructans are main WSC. But under drought, sucrose increasedin root apices for Md and Pp which showed higher contents

than control tubes. Fructans

increase was observed for Tf, Pp, Dg and Pt, but Tf remained lower than the control.

0 20 40 60 80 100 120 140 160 180 Control at rehydration

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0 10 20 30 40 50 Control at rehydration

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0 20 40 60 80 100 120 140 160 180 Control at rehydration ns ns

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0 10 20 30 40 50 Control at rehydration ns ns

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Fructans and sucrose are higher in basal leaf meristems than in roots

and apices. Drought induced

sucrose accumulation for each

species, with highest contents in

Pp and Tf. Fructans content was

stable but increased in Md.

Although fructansdidnot accumulatein

roots, fructans with high degree of polymerization (HDP >5) contributed to roots cell integrity, except for Pt.

M a in r e s u lt s 0 20 40 60 80 100 0 2 0 4 0 6 0 8 0

Root HDP-fructanes content (mg/g DM)

R o o t m e m b ra n e s ta b ili ty ( % ) Dg Fa Md Pp Tf To Dg Fa Md Pp Pt Tf To P-Value *** *** *** *** ns *** *** R² 0.44 0.40 0.46 0.48 -0.42 0.35