TRANSITION4WOOD:*the*lord* of*the*ring*?**

Guillermina*Dalla*Salda* Alejandro*Mar2nez4Meier* María*Elena*Fernández* Anne4Sophie*Sergent* Philippe*Rozenberg**

INTRODUCTION' !  Wood* in* conifers* is* formed* by* one* type* of* cells* that* show* different* characteris2cs* in* rela2on* to* the*condi2ons*under*which*they*were*formed.* * * !  Tree4rings* * are* a* con$nuous' varia$on' of* cell* dimensions*that*is*oNen*simplified*in:*earlywood* and*latewood,*but*in4between*them*we*can*also* determine*a*third*part:*transi2on4wood.* !  *Wood*cell*structure*determines*wood*density.* !  In* Douglas* fir* wood* density* is* related* to** cavita2on* resistance* that* is* a* relevant* trait* for* drought*resistance*in*trees.*

INTRODUCTION' How* do* earlywood,* transi2on4wood* and* latewood*deal*with*increasing*xylem*tension?*

* * Addressing*this*ques2on*is*important*to*understand*how* hydraulic* safety* func2ons* within* the* growth* ring* and* therefore* the* role* of* latewood,* earlywood* and* transi2on4wood*in*terms*of*drought*resistance.*

50*Douglas4fir*trees*of*10*different*gene2c* en22es*in*Patagonia,*Argen2na* 2011*tree4ring* 4*VULNERABLE* 4*RESISTANT*

100

PLC*(%)*

80

60

40

0 1 2 2.5 3 3.5

20

MPa* 0 -5

-4

-3

-2

-1

0

pressure*(Mpa)*

MATERIAL'&'METHODS'

MPa*

•  *Subsequently*the*conduc2ve*area*was*stained*by*introducing*through*the* sample*an*aqueous*colored*solu2on*(1*%*phloxine*solu2on).** MPa*

MPa*

0*********1*********2*********2.5******3*******3.5*

0*********1*********2*********2.5******3*******3.5*

Latewood* Transi2on4wood* Earlywood*

•  *Samples*were*then*oven*dried*and*polished*and*wood*surface*was*digitalized.* Images*were*further*treated*(ImageJ)*and*the*%*of*colored*area*was*assessed*in* each*type*of*wood.***

MATERIAL'&'METHODS'

2008

2009

2010

2011

0.4

0.6

2007

0.2

profil

0.8

pe49b.pxb microdensity*profile*

0

length*(x*24μm)**

500

1000

max*

x.profil

2011*tree–rings* was*divided*in* three*parts:* earlywood,* transi2on4wood* and*latewood**

1500

MDP3*

MDP1* MDP2* min*

MATERIAL'&'METHODS'

Resistant Vulnerable

%*of*non*conduc2ve*area**

100

Earlywood Transition-wood

75

Latewood

50

25

0 0

1

2

2.5

3

3.5

Pressure (Mpa)

RESULTS'

P0

P50

P88

Eric Badel PIAF - INRA X-Ray Microtomography

RESULTS'

Standardized*tree4rings***

0.8

density*(g/cm3 )**

Vulnerable 0.6

0.4

Resistant

0.2

0

5

10

15

20

length*(x24µm )**

RESULTS'

25

30

DISCUSSION' Assuming:* * %*of*conduc2ve*area* *

= propaga2on*of*xylem*cavita2on*

In* Douglas4fir,* cavita2on* propaga2on* would* not* follow*a*trend*related*to*cell*dimensions,*but*would* rather*follow*a*latewood4earlywood4transi2on4wood* sequence,*extending*from*the*boundaries*of*the*ring* towards*the*inner*part*of*the*ring.*

DISCUSSION' Assuming:* * %*of*conduc2ve*area* *

= propaga2on*of*xylem*cavita2on*

In* Douglas4fir,* cavita2on* propaga2on* would* not* follow*a*trend*related*to*cell*dimensions,*but*would* rather*follow*a*latewood4earlywood4transi2on4wood* sequence,*extending*from*the*boundaries*of*the*ring* towards*the*inner*part*of*the*ring.*

CONCLUSION' •  * * * Significant* differences* between* resistant* and* vulnerable* to* cavita2on* individuals* were* observed* only* in* the* transi2on4wood* por2on*of*the*ring.** • * * * Transi2on4wood,* in Douglas Fir,* would* have* a* key* role* in* differen2al* resistance* to* cavita2on* 4* and* therefore,* to* drought4*

density*(g/*cm3)**

which*deserves*further*inves2ga2on.*

length*(x*24μm)**

THANK*YOU*!!*