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					樹形や導管間の連絡による水輸送パ
   ターンへの影響を考える
 -つる植物、クズを用いた解析例


      種子田春彦
   東京大学・院・理 寺島研
      (ポスドク)
         生理生態学の観点からわかること
                       進化や生態学的現象
                                   生態学のKeywords
                                    生産性が
                                   ・生産性が高い
              器官や組織の機能              効率が
                                   ・効率が高い
空間スケール
空間スケール




                                    成長速度が
                                   ・成長速度が高い
          生理学的性質
          形態学的特徴


                             個体から群集レベルでの現象の
                            メカニズムを生理学な現象から明
                            らかにする



                   時間スケール
                   時間スケール
光合成は、蒸散による大量の水の消費を
      必要とする.

                • 水利用効率
                 (1 gの炭水化物を固定するた
                  めに必要な水の量)

                針葉樹 :200-300 g
                落葉広葉樹
                   :300-400 g
  CO2   Water   草本 :700-1000 g

  葉の断面図
通導抵抗は大きいので、葉は強い原動力
  を使って水をなんとか引き上げる.

  Leaf water potential (MPa)
                           )   Transpiration rate (mmol m-2 s-1)




                                                                   草本

                                                                   硬い茎を持つ草本
                                                                   低木

                                                                   落葉広葉樹

                                                                   落葉針葉樹
                                                                   常緑針葉樹
A leaf pulls water competing for water
           with other leaves.
                   • Distal leaves are under
                     great disadvantages.
                        Because…
                   1) Water transport distance is
                      long.
                   2) Gravitational force is large.

                   3) Motive force is limited at a
                      certain value.
      Today’s Question

How do distal leaves compete for
   water with basal leaves?
Water transport networks should be
        arranged properly.

• Sectoriality
 -Segmentation of water transport pathway


• Hydraulic architecture
 -Arrangements of hydraulic resistance in a
 shoot.
  ‘Sectoriality’ depends on magnitude of
 transverse movement of water in xylem.




   Sectored                   Interconnected
(Independent)
Interconnection sites between conduits
    are less often and impermeable.




                                 Kudzu
  Chances of interconnecting may
increase with long running distance.



                    • A vessel runs connecting
                      with several different ones.
                    • Sites where vessels are
                      interconnecting are long.



                Running pattern of vessels in Fagus wood
                     (Tyree and Zimmermann 2002)
 Hydraulic architecture depends on the
  morphological features of conduits

1) Vessel diameter
     Hydraulic conductivity is the fourth-power of vessel
     lumen diameter.


2) Vessel length
     Hydraulic conductivity increasing with frequency of
     vessel end where water passes through the pit
     membrane of pit pore.
           Hydraulic conductance
main stem > branch > junction > petiole > leaf lamina




               Tyree and Zimmermann (2002)
Hydraulic architecture prevents hydraulic
         patterns from favoring.

              • The frictions at branch junctions
                can function as a valve.
              • A main stem has larger leaf
                specific conductance (LSC)
                than lateral branches, causing
                more water to flow axially.

               LSC (leaf specific conductivity) =
                       hydraulic conductivity
                          distal foliage area
                  Zimmermann (1978)
‘Sectoriality’ and ‘hydraulic architecture’
          vary among species.
Current-year shoot of Kudzu is suitable
 for study on long-distance transport.
         ● Shoot is >15 m long and few branching.
         ● One can treat in the laboratory easily.
         ● Shoot form is very simple.
                        Simple shoot form of kudzu vine
petiole / leaf lamina




                                                                                                   15 c
Lateral branches:




                                                                                                       m
                                                                                                           40 cm




                                                                                  A main stem: stem (internodes)
                                                           1.2                                                           550
                        Leaf area of distal foliage (m )




                                                                                                                         500
                        2




                                                            1
                                                                                                                         450
                                                           0.8
                                                                                                           SLA (cm /g)
                                                                                                           2             400

                                                           0.6                                                           350

                                                                                                                         300
                                                           0.4
                                                                                                                         250
                                                           0.2
                                                                                                                         200

                                                            0                                                            150
                                                                 0         5           10          15                          0   10       20        30   40
                                                                     Distance from shoot tip (m)                                        Node number
  In an internode-to-leaf pathway, water
  passes via interconnections of vessels.
                                               Leaf



Secondary xylem
    vessels
 Primary xylem
    vessels




  Water from roots passes through secondary xylem vessels,
    which do not connect with leaf trace vessels directly.
 How do distal leaves compete for
    water with basal leaves?
           In case of Kudzu vine
• Sectoriality
 -Magnitude of connections between conduits.


• Hydraulic architecture
 -Arrangements of hydraulic resistance in a
 shoot.
 How do distal leaves compete for
    water with basal leaves?
           In case of Kudzu vine
• Sectoriality
 -Magnitude of connections between conduits.


• Hydraulic architecture
 -Arrangements of hydraulic resistance in a
 shoot.
   Scheme of sectored flow in
   internode-to-leaf pathways




   Sectored          Interconnected
(Independent)
  Do leaf trace vessels connect with
      secondary xylem vessels?
                                         Suction by
                                         partial vacuum




 Safranin




Yes, Transverse movement of dye among primary and
secondary vessels were observed within an internode.
How many secondary xylem vessels do
  leaf trace vessels connect with?
                                    Suction
          11cm      7cm     3cm




                                                     Safranin




         33cm       27cm     19cm             15cm



About 80% of secondary xylem vessels have access
      with leaf trace vessels within an internode.
Dyed patterns indicate the distribution
of interconnections between vessels.

                                  A leaf pulls
                                     water.

                                            Safranin dye




     Dye solution should move to a leaf where
strongest tension occurs at the minimum distance.
 Where do interconnecting sites occur?



           values at 1.0 of fraction of internode length
             The number of dyed vessels relative to
                                                            1

                                                           0.8

                                                           0.6

                                                           0.4

                                                           0.2

                                                            0
                                                            -0.4 -0.2      0   0.2   0.4   0.6   0.8   1   1.2
                                                                        Fraction of internode length




Interconnecting sites were evenly                                                            distributed along
an internode.
Measurements of internode-to-petiole hydraulic
   conductance in shortening internode.




       If interconnections are important on water
    transport to a leaf, shortening treatment should
           decrease the hydraulic conductance.
Do interconnections contribute to water
        transport quantitatively?
                                                      1.2
    Hydraulic conductivity relative to
       Hydraulic conductivity relative to kh (N) at
                                                       1
             values at 25 cm

                                                      0.8
                         25cm




                                                      0.6


                                                      0.4                                                     順方向
                                                                                                              逆方向

                                                      0.2


                                                       0
                                                            0   5         10          15          20         25     30
                                                                Distance from a basal end of segment to node (cm)
                                                                          Internode length (cm)

Yes. Interconnections help effective transport from an
                                                                    internode to a leaf.
  Large magnitude of transverse
 movement of water in xylem was
     observed in kudzu vine.




   Sectored           Interconnected
(Independent)
         Theoretical models predict the flow via
         independent and interconnected xylem
                at a whole-shoot scale.
(b) Independent model




               RP(5)    RP(4)    RP(3)     RP(2)     RP(1)           RP(5)     RP(4)     RP(3)    RP(2)     RP(1)


                                                             RI(5)     RI(4)     RI(3)    RI(2)     RI(1)




       RB(5)    RB(4)    RB(3)     RB(2)     RB(1)


              Sectored                                           Interconnected
           (Independent)
  For parameters of calculations, measured
  hydraulic conductance values were used.
                                             2000
                                                        (a) KI


                                             1500
                                                                                                        (e) Measurement of
                                                                                                      (a) Measurement of KI KI

                                             1000
                                                                                                        0.002 MPa
                                             500                                     0.65
                                                                           y = 160.2 x
Hydraulic conductance (mg H 2O MPa -1 s-1)




                                                                               2
                                                                           R       = 0.64

                                               0
                                                        (b) KP
                                              20                                                       (c) Measurement of K
                                                                                                      (b) Measurement of KIP
                                                                                                                           Ip
                                              15

                                                                                                        0.008 MPa
                                              10



                                               5                                        0.12
                                                                               y = 8.06 x
                                                                               R   2
                                                                                       = 0.028
                                                                                                        Kp values were obtained by subtraction of KI from KIP
                                               0
                                                        (c) KB

                                              80
                                                                                                      (c) Measurement of KB
                                              60
                                                                                                                          KI
                                              40
                                                                                                          KB =
                                              20
                                                                           R
                                                                                     -0.35
                                                                           y = 160.2 x
                                                                               2
                                                                                   = 0.34
                                                                                                               The number of distal nodes
                                               0
                                                    0            10   20               30        40

                                                                 Node number
 Both models predict the favored
patterns by different mechanisms.

                                     12
                                                   Interconnected model
                                     10            Independent model
   Hydraulic conductance
                           s -1)

                                           8
                           -1
                            (mg H 2O MPa




                                           6


                                           4


                                           2


                                           0
                                               0    10            20      30   40
                                                          Node number
Flow patterns in a shoot base-to-petiole
      pathway were measured.
                               Flow was generated by 0.2
                               MPa of a positive pressure.
                                  Pressure chamber




                        Mass flow from petiole cut ends
                          were measured for 3min.
                                                         Which model are measured KBP
                                                           patterns explained more?
                                                                                                                                                    14
                                          12            (a)                                                                                                      (b)
                                                                                                                                                    12




                                                                                                Predicted hydraulic conductance
                                                               Measurement
                                          10                   Interconnected model
                                                                                                                                                    10




                                                                                                                                  (mg H 2O MPa -1 s-1)
Hydraulic conductance




                                                               Independent model
                        (mg H 2O MPa -1 s -1)




                                                8
                                                                                                                                                         8

                                                6
                                                                                                                                                         6

                                                4                                                                                                        4

                                                                                                                                                                                    Independent model
                                                2                                                                                                        2                          Interconnected model
                                                                                                                                                                                             1:1

                                                0                                                                                                        0
                                                    0         10          20          30   40                                                                0     2    4     6     8     10      12       14
                                                                                                                                                                  Measured hydraulic conductance
                                                                   Node number
                                                                                                                                                                        (mg H 2O MPa -1 s-1)



                                                    Interconnected model. Kudzu vine exhibited
                                      water transport patterns assuming interconnecting xylem.
 Why does sectored vascular pattern
  favor water supply at basal node?
(b) Independent model


                                                             Total conductance of one
                                                             pipe (vascular bundle)

                                                                                   1
               RP(5)    RP(4)    RP(3)     RP(2)     RP(1)
                                                               K TOT =  
                                                                       RL + ∑ RB (i )
                                                                              KI
                                                             KB =
                                                                    The number of distal nodes
       RB(5)    RB(4)    RB(3)     RB(2)     RB(1)




  For water supply in tune with transpiration demand…
                                     RL >> ∑RB is required.
In kudzu, sectored flow was offset by large
magnitude of transverse water movement.
 Because …                 Extent of interconnecting
 ・Long internodes          should vary among wood
 ・Short distance between   features.
 vessels.
 How do distal leaves compete for
    water with basal leaves?
           In case of Kudzu vine
• Sectoriality
 -Magnitude of connections between conduits.


• Hydraulic architecture
 -Arrangements of hydraulic resistance in a
 shoot.
    Measurements of KI, KP and KL
 (an internode, a petiole and a lamina)
         (e) Measurement of K
      a) Measurements of KI I

          0.002 MPa


       (c) Measurement of IP
      b) Measurements of KKIP

         0.008 MPa


         K Measurement subtraction: KP = 1/(1/KIP – 1/KI)
       (d) P is obtained byof K

      c) Measurements of KL

     Transpiration rate (mmol m −2 s −1 )
KL =
        Leaf water potential (MPa )
                                            Vacuum pump method (Sack et al. 2002)
LSC of internodes values are higher than those
  of petioles and leaf lamina in kudzu vine.
                                            1000
                                 )
                                -1
                                 s
                                -2
    Leaf-specific conductance




                                             100
                                 m




                                                                                                    Internodes
                                -1
                                (mmol MPa




                                                                                                    Petioles

                                              10

                                                                                                    Leaf lamina


                                               1
                                                   0   5   10   15    20      25   30   35   40

                                                                Node number




                                                           Internodes                             Petiole
           Measurements of KBP
       (shoot base-to-petiole pathway)

Outflow from petioles were measured
through a shoot when the flow was forced
from its stem base at positive pressure of
0.2 MPa.



                  0.2 MPa
Is water transported equally to all nodes in
    a shoot base-to-petiole pathway?
                                                             100


                                          -to-petiole path
                  relative to values at 3rd node
                                                              10
         Hydraulic conductance of stem




                                                               1




                                                             0.1
                                                                   0   5   10   15   20   25   30   35   40
                                                                                Node number

  No.   Hydraulic architecture of shoot base-to-petiole
  pathways favors KBP at basal nodes.
           Measurements of KW
         (whole-plant conductance)
Whole-plant conductance and
diurnal patterns of transpiration
rate were measured at three
points in a shoot




           Transpiration rate (mmol m −2 s −1 )
      KW =
              Leaf water potential (MPa )
                           Soil water potential is assumed to be zero.
                                        Are KW values favored at basal nodes,
                                                 as KBP values did?
                                                                                                                                                                                        14
                                    0     5   10   15    20   25   30
                               0                                                                     12                                                                                 12                KW




                                                                                                                                            Whole-plant conductance
                                        Leaf water potential                                                  Transpiration rate




                                                                                                                                                                      (mmol m MPa s )
                                                                                                                                                                      -1
                                                                        s )
                                                                        -1
                             -0.2
                                                                                                     10                                                                                 10




                                                                                                                                                                      -1
                                                                        -2
Leaf water potential (MPa)




                             -0.4




                                                                        Transpiration rate (mmol m
                                                                                                     8                                                                                  8
                             -0.6




                                                                                                                                                                      -2
                             -0.8                                                                    6                                                                                  6

                              -1                                                                                                                                                        4
                                                                                                     4
                             -1.2
                                                                                                     2                                                                                  2
                             -1.4

                                                                                                     0                                                                                  0
                             -1.6
                                                                                                          0    5   10   15   20   25   30                                                    0   5   10   15   20   25   30

                                                                                                                        Node number
                                          Measurements started at…
                                                        8:30 a.m. -                                                10:00 a.m. -                                                              11:30 a.m. -

                                         No. KW of mature leaves did not largely reduce toward
                                         the shoot tip.
                        Can hydraulic architecture of whole-plant
                         path supply water equally to all leaves?
●Diurnal changes in transpiration rate                                                                ● Whole-plant conductance at 9:00 a.m..
                                                                                                                             6
                                  7
 Transpiration rate (mmol m s )
 -1




                                                                                                                                                    n.s. by ANOVA
                                                                                    Terminal
 -2




                                  6                                                                                          5




                                                                                                   Whole-plant conductance
                                                                                    Middle




                                                                                                    (mmol m -2 s-1 MPa -1)
                                  5                                                 Basal                                    4
                                  4
                                                                                                                             3
                                  3
                                                                                                                             2
                                  2
                                  1                                                                                          1

                                  0                                                                                          0
                                   6:00   7:30   9:00   10:30   12:00   13:30   15:00   16:30                                    Terminal        Middle             Basal

                                                        Time of Day (h:m)


                                                           terminal leaf                        Middle leaf                                 Basal leaf




                                             Yes.  Transpiration rate and KW values are not
                                             dependent on positions of the shoot.
      Hydraulic architecture of kudzu is
     modeled by electrical circuit analogy
                  Hydraulic resistance
                   of petiole or lamina
  Hydraulic resistance
      of internode
                                          …   …


                                          …   …


• The modeled flow assumes that all leaves pull water
  at the same motive force.
                                   Measured values of KI, KP and KL were
                                          used for calculations
                                   1000
 s )
-1 -1




                                                                                      Internode
                                    100
 Hydraulic conductance (mmol MPa




                                                                                      Petiole
                                                                                       + petiole junction
                                     10
                                                                                      Leaf lamina
                                      1



                                    0.1                                              KI >> KP >> KL
                                   0.01
                                          0   5   10   15   20   25   30   35   40
                                                       Node number
Can the difference between two pathways
   be explained by the circuit model?
                                                50
Hydraulic conductance of stem base-to-petiole




                                                                                                                                    2.5
                                                         Shoot base-to-petiole path




                                                                                              Whole-plant conductance relative to
      path relative to values at 5th node




                                                40                                                                                   2




                                                                                                      values at node 9th
                                                30                                                                                  1.5


                                                20                                                                                   1


                                                10                                                                                  0.5
                                                                                                                                              Root-to-leaf lamina path
                                                 0                                                                                   0
                                                     0     5   10   15   20   25   30    35                                               0   5   10   15   20   25   30   35

                                                                                        Node number
                    Yes, Favoring of hydraulic patterns was largely improved
                          when leaf laminas are involved in the transport pathways.
 Large resistance of leaf lamina prevents
  water supply from favoring in a shoot.

● Axial conductance >> Radial conductance




● Axial conductance ≧ Radial conductance
How do distal leaves compete for water
  with basal leaves in kudzu shoot?
  ΨL
        KL(1)   KL(2)    KL(3)    KL(4)       KL(5)


        ΨX(1)   ΨX(2)    ΨX(3)    ΨX(4)      ΨX(5)         ΨXB

        Water supply at node i = K L (i ) ⋅ (ΨL − ΨX (i ) )
 i) KL << KI Hydraulic patterns is not favored.
  ∵ Lateral flow << Axial flow            Change in ΨX is very slight.

 ii) KL << KI Hydraulic patterns is largely favored.
  ∵ Lateral flow < Axial flow             Change in ΨX is large.
                   Conclusions
● Sectoriality
Large amount of transverse movement of water in xylem results
in low extent of sectoriality.




● Hydraulic architecture
Large resistance of leaf lamina enables water from soil to supply
to leaves in tune with their transpiration demand.

				
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posted:8/9/2011
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